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<H1>Autoconf</H1>
<H2>Creating Automatic Configuration Scripts</H2>
<H2>Edition 2.53, for Autoconf version 2.53</H2>
<H2>8 March 2002</H2>
<ADDRESS>David MacKenzie</ADDRESS>
<ADDRESS>Ben Elliston</ADDRESS>
<ADDRESS>Akim Demaille</ADDRESS>
<P>
<P><HR><P>
<H1><A NAME="SEC1" HREF="autoconf_toc.html#TOC1">Introduction</A></H1>
<PRE>
A physicist, an engineer, and a computer scientist were discussing the
nature of God. ``Surely a Physicist,'' said the physicist, ``because
early in the Creation, God made Light; and you know, Maxwell's
equations, the dual nature of electromagnetic waves, the relativistic
consequences...'' ``An Engineer!,'' said the engineer, ``because
before making Light, God split the Chaos into Land and Water; it takes a
hell of an engineer to handle that big amount of mud, and orderly
separation of solids from liquids...'' The computer scientist
shouted: ``And the Chaos, where do you think it was coming from, hmm?''
---Anonymous
</PRE>
<P>
Autoconf is a tool for producing shell scripts that automatically
configure software source code packages to adapt to many kinds of
UNIX-like systems. The configuration scripts produced by Autoconf
are independent of Autoconf when they are run, so their users do not
need to have Autoconf.
<P>
The configuration scripts produced by Autoconf require no manual user
intervention when run; they do not normally even need an argument
specifying the system type. Instead, they individually test for the
presence of each feature that the software package they are for might need.
(Before each check, they print a one-line message stating what they are
checking for, so the user doesn't get too bored while waiting for the
script to finish.) As a result, they deal well with systems that are
hybrids or customized from the more common UNIX variants. There is
no need to maintain files that list the features supported by each
release of each variant of UNIX.
<P>
For each software package that Autoconf is used with, it creates a
configuration script from a template file that lists the system features
that the package needs or can use. After the shell code to recognize
and respond to a system feature has been written, Autoconf allows it to
be shared by many software packages that can use (or need) that feature.
If it later turns out that the shell code needs adjustment for some
reason, it needs to be changed in only one place; all of the
configuration scripts can be regenerated automatically to take advantage
of the updated code.
<P>
The Metaconfig package is similar in purpose to Autoconf, but the
scripts it produces require manual user intervention, which is quite
inconvenient when configuring large source trees. Unlike Metaconfig
scripts, Autoconf scripts can support cross-compiling, if some care is
taken in writing them.
<P>
Autoconf does not solve all problems related to making portable software
packages--for a more complete solution, it should be used in concert
with other GNU build tools like Automake and Libtool. These other tools
take on jobs like the creation of a portable, recursive <TT>`Makefile'</TT>
with all of the standard targets, linking of shared libraries, and so
on. See section <A HREF="autoconf.html#SEC2">The GNU build system</A>, for more information.
<P>
Autoconf imposes some restrictions on the names of macros used with
<CODE>#if</CODE> in C programs (see section <A HREF="autoconf.html#SEC186">Preprocessor Symbol Index</A>).
<P>
Autoconf requires GNU M4 in order to generate the scripts. It uses
features that some UNIX versions of M4, including GNU M4 1.3,
do not have. You must use version 1.4 or later of GNU M4.
<P>
See section <A HREF="autoconf.html#SEC151">Upgrading From Version 1</A>, for information about upgrading from version 1.
See section <A HREF="autoconf.html#SEC174">History of Autoconf</A>, for the story of Autoconf's development.
See section <A HREF="autoconf.html#SEC169">Questions About Autoconf</A>, for answers to some common questions about Autoconf.
<P>
See the @href{http://www.gnu.org/software/autoconf/autoconf.html,
Autoconf web page} for up-to-date information, details on the mailing
lists, pointers to a list of known bugs, etc.
<P>
Mail suggestions to <A HREF="mailto:autoconf@gnu.org">the Autoconf mailing
list</A>.
<P>
Bug reports should be preferably submitted to the
@href{http://sources.redhat.com/cgi-bin/gnatsweb.pl?database=autoconf,
Autoconf Gnats database}, or sent to <A HREF="mailto:bug-autoconf@gnu.org">the
Autoconf Bugs mailing list</A>. If possible, first check that your bug is
not already solved in current development versions, and that it has not
been reported yet. Be sure to include all the needed information and a
short <TT>`configure.ac'</TT> that demonstrates the problem.
<P>
Autoconf's development tree is accessible via CVS; see the Autoconf
web page for details. There is also a
@href{http://subversions.gnu.org/cgi-bin/cvsweb/autoconf/, CVSweb
interface to the Autoconf development tree}. Patches relative to the
current CVS version can be sent for review to the
<A HREF="mailto:autoconf-patches@gnu.org">Autoconf Patches mailing list</A>.
<P>
Because of its mission, Autoconf includes only a set of often-used
macros that have already demonstrated their usefulness. Nevertheless,
if you wish to share your macros, or find existing ones, see the
@href{http://www.gnu.org/software/ac-archive/, Autoconf Macro
Archive}, which is kindly run by <A HREF="mailto:simons@computer.org">Peter Simons</A>.
<H1><A NAME="SEC2" HREF="autoconf_toc.html#TOC2">The GNU build system</A></H1>
<P>
Autoconf solves an important problem--reliable discovery of
system-specific build and runtime information--but this is only one
piece of the puzzle for the development of portable software. To this
end, the GNU project has developed a suite of integrated utilities to
finish the job Autoconf started: the GNU build system, whose most
important components are Autoconf, Automake, and Libtool. In this
chapter, we introduce you to those tools, point you to sources of more
information, and try to convince you to use the entire GNU build system
for your software.
<H2><A NAME="SEC3" HREF="autoconf_toc.html#TOC3">Automake</A></H2>
<P>
The ubiquity of <CODE>make</CODE> means that a <CODE>Makefile</CODE> is almost the
only viable way to distribute automatic build rules for software, but
one quickly runs into <CODE>make</CODE>'s numerous limitations. Its lack of
support for automatic dependency tracking, recursive builds in
subdirectories, reliable timestamps (e.g. for network filesystems), and
so on, mean that developers must painfully (and often incorrectly)
reinvent the wheel for each project. Portability is non-trivial, thanks
to the quirks of <CODE>make</CODE> on many systems. On top of all this is the
manual labor required to implement the many standard targets that users
have come to expect (<CODE>make install</CODE>, <CODE>make distclean</CODE>,
<CODE>make uninstall</CODE>, etc.). Since you are, of course, using Autoconf,
you also have to insert repetitive code in your <CODE>Makefile.in</CODE> to
recognize <CODE>@CC@</CODE>, <CODE>@CFLAGS@</CODE>, and other substitutions
provided by @command{configure}. Into this mess steps <EM>Automake</EM>.
<A NAME="IDX1"></A>
<P>
Automake allows you to specify your build needs in a <CODE>Makefile.am</CODE>
file with a vastly simpler and more powerful syntax than that of a plain
<CODE>Makefile</CODE>, and then generates a portable <CODE>Makefile.in</CODE> for
use with Autoconf. For example, the <CODE>Makefile.am</CODE> to build and
install a simple "Hello world" program might look like:
<PRE>
bin_PROGRAMS = hello
hello_SOURCES = hello.c
</PRE>
<P>
The resulting <CODE>Makefile.in</CODE> (~400 lines) automatically supports all
the standard targets, the substitutions provided by Autoconf, automatic
dependency tracking, <CODE>VPATH</CODE> building, and so on. <CODE>make</CODE> will
build the <CODE>hello</CODE> program, and <CODE>make install</CODE> will install it
in <TT>`/usr/local/bin'</TT> (or whatever prefix was given to
@command{configure}, if not <TT>`/usr/local'</TT>).
<P>
Automake may require that additional tools be present on the
<EM>developer's</EM> machine. For example, the <CODE>Makefile.in</CODE> that
the developer works with may not be portable (e.g. it might use special
features of your compiler to automatically generate dependency
information). Running <CODE>make dist</CODE>, however, produces a
<TT>`hello-1.0.tar.gz'</TT> package (or whatever the program/version is)
with a <CODE>Makefile.in</CODE> that will work on any system.
<P>
The benefits of Automake increase for larger packages (especially ones
with subdirectories), but even for small programs the added convenience
and portability can be substantial. And that's not all...
<H2><A NAME="SEC4" HREF="autoconf_toc.html#TOC4">Libtool</A></H2>
<P>
Very often, one wants to build not only programs, but libraries, so that
other programs can benefit from the fruits of your labor. Ideally, one
would like to produce <EM>shared</EM> (dynamically-linked) libraries,
which can be used by multiple programs without duplication on disk or in
memory and can be updated independently of the linked programs.
Producing shared libraries portably, however, is the stuff of
nightmares--each system has its own incompatible tools, compiler flags,
and magic incantations. Fortunately, GNU provides a solution:
<EM>Libtool</EM>.
<A NAME="IDX2"></A>
<P>
Libtool handles all the requirements of building shared libraries for
you, and at this time seems to be the <EM>only</EM> way to do so with any
portability. It also handles many other headaches, such as: the
interaction of <CODE>Makefile</CODE> rules with the variable suffixes of
shared libraries, linking reliably to shared libraries before they are
installed by the superuser, and supplying a consistent versioning system
(so that different versions of a library can be installed or upgraded
without breaking binary compatibility). Although Libtool, like
Autoconf, can be used on its own, it is most simply utilized in
conjunction with Automake--there, Libtool is used automatically
whenever shared libraries are needed, and you need not know its syntax.
<H2><A NAME="SEC5" HREF="autoconf_toc.html#TOC5">Pointers</A></H2>
<P>
Developers who are used to the simplicity of <CODE>make</CODE> for small
projects on a single system might be daunted at the prospect of learning
to use Automake and Autoconf. As your software is distributed to more
and more users, however, you will otherwise quickly find yourself
putting lots of effort into reinventing the services that the GNU build
tools provide, and making the same mistakes that they once made and
overcame. (Besides, since you're already learning Autoconf, Automake
will be a piece of cake.)
<P>
There are a number of places that you can go to for more information on
the GNU build tools.
<UL>
<LI>Web
The home pages for
@href{http://www.gnu.org/software/autoconf/,Autoconf},
@href{http://www.gnu.org/software/automake/,Automake}, and
@href{http://www.gnu.org/software/libtool/,Libtool}.
<LI>Automake Manual
See section `Automake' in <CITE>GNU Automake</CITE>, for more
information on Automake.
<LI>Books
The book <CITE>GNU Autoconf, Automake and Libtool</CITE><A NAME="DOCF1" HREF="autoconf_foot.html#FOOT1">(1)</A>
describes the complete GNU build environment. You can also find the
entire book on-line at @href{http://sources.redhat.com/autobook/,"The
Goat Book" home page}.
<LI>Tutorials and Examples
The @href{http://sources.redhat.com/autoconf/,Autoconf Developer Page}
maintains links to a number of Autoconf/Automake tutorials online, and
also links to the @href{http://www.gnu.org/software/ac-archive/,
Autoconf Macro Archive}.
</UL>
<H1><A NAME="SEC6" HREF="autoconf_toc.html#TOC6">Making @command{configure} Scripts</A></H1>
<P>
<A NAME="IDX3"></A>
<A NAME="IDX4"></A>
<P>
The configuration scripts that Autoconf produces are by convention
called @command{configure}. When run, @command{configure} creates several
files, replacing configuration parameters in them with appropriate
values. The files that @command{configure} creates are:
<UL>
<LI>
one or more <TT>`Makefile'</TT> files, one in each subdirectory of the
package (see section <A HREF="autoconf.html#SEC22">Substitutions in Makefiles</A>);
<LI>
optionally, a C header file, the name of which is configurable,
containing <CODE>#define</CODE> directives (see section <A HREF="autoconf.html#SEC27">Configuration Header Files</A>);
<LI>
a shell script called <TT>`config.status'</TT> that, when run, will recreate
the files listed above (see section <A HREF="autoconf.html#SEC145">Recreating a Configuration</A>);
<LI>
an optional shell script normally called <TT>`config.cache'</TT>
(created when using <SAMP>`configure --config-cache'</SAMP>) that
saves the results of running many of the tests (see section <A HREF="autoconf.html#SEC84">Cache Files</A>);
<LI>
a file called <TT>`config.log'</TT> containing any messages produced by
compilers, to help debugging if @command{configure} makes a mistake.
</UL>
<P>
<A NAME="IDX5"></A>
<A NAME="IDX6"></A>
To create a @command{configure} script with Autoconf, you need to write an
Autoconf input file <TT>`configure.ac'</TT> (or <TT>`configure.in'</TT>) and run
@command{autoconf} on it. If you write your own feature tests to
supplement those that come with Autoconf, you might also write files
called <TT>`aclocal.m4'</TT> and <TT>`acsite.m4'</TT>. If you use a C header
file to contain <CODE>#define</CODE> directives, you might also run
@command{autoheader}, and you will distribute the generated file
<TT>`config.h.in'</TT> with the package.
<P>
Here is a diagram showing how the files that can be used in
configuration are produced. Programs that are executed are suffixed by
<SAMP>`*'</SAMP>. Optional files are enclosed in square brackets (<SAMP>`[]'</SAMP>).
@command{autoconf} and @command{autoheader} also read the installed Autoconf
macro files (by reading <TT>`autoconf.m4'</TT>).
<P>
Files used in preparing a software package for distribution:
<PRE>
your source files --> [autoscan*] --> [configure.scan] --> configure.ac
configure.ac --.
| .------> autoconf* -----> configure
[aclocal.m4] --+---+
| `-----> [autoheader*] --> [config.h.in]
[acsite.m4] ---'
Makefile.in -------------------------------> Makefile.in
</PRE>
<P>
Files used in configuring a software package:
<PRE>
.-------------> [config.cache]
configure* ------------+-------------> config.log
|
[config.h.in] -. v .-> [config.h] -.
+--> config.status* -+ +--> make*
Makefile.in ---' `-> Makefile ---'
</PRE>
<H2><A NAME="SEC7" HREF="autoconf_toc.html#TOC7">Writing <TT>`configure.ac'</TT></A></H2>
<P>
To produce a @command{configure} script for a software package, create a
file called <TT>`configure.ac'</TT> that contains invocations of the
Autoconf macros that test the system features your package needs or can
use. Autoconf macros already exist to check for many features; see
section <A HREF="autoconf.html#SEC35">Existing Tests</A>, for their descriptions. For most other features,
you can use Autoconf template macros to produce custom checks; see
section <A HREF="autoconf.html#SEC68">Writing Tests</A>, for information about them. For especially tricky
or specialized features, <TT>`configure.ac'</TT> might need to contain some
hand-crafted shell commands; see section <A HREF="autoconf.html#SEC110">Portable Shell Programming</A>. The
@command{autoscan} program can give you a good start in writing
<TT>`configure.ac'</TT> (see section <A HREF="autoconf.html#SEC11">Using @command{autoscan} to Create @file{configure.ac}</A>, for more information).
<P>
Previous versions of Autoconf promoted the name <TT>`configure.in'</TT>,
which is somewhat ambiguous (the tool needed to produce this file is not
described by its extension), and introduces a slight confusion with
<TT>`config.h.in'</TT> and so on (for which <SAMP>`.in'</SAMP> means "to be
processed by @command{configure}"). Using <TT>`configure.ac'</TT> is now
preferred.
<H3><A NAME="SEC8" HREF="autoconf_toc.html#TOC8">A Shell Script Compiler</A></H3>
<P>
Just as for any other computer language, in order to properly program
<TT>`configure.ac'</TT> in Autoconf you must understand <EM>what</EM> problem
the language tries to address and <EM>how</EM> it does so.
<P>
The problem Autoconf addresses is that the world is a mess. After all,
you are using Autoconf in order to have your package compile easily on
all sorts of different systems, some of them being extremely hostile.
Autoconf itself bears the price for these differences: @command{configure}
must run on all those systems, and thus @command{configure} must limit itself
to their lowest common denominator of features.
<P>
Naturally, you might then think of shell scripts; who needs
@command{autoconf}? A set of properly written shell functions is enough to
make it easy to write @command{configure} scripts by hand. Sigh!
Unfortunately, shell functions do not belong to the least common
denominator; therefore, where you would like to define a function and
use it ten times, you would instead need to copy its body ten times.
<P>
So, what is really needed is some kind of compiler, @command{autoconf},
that takes an Autoconf program, <TT>`configure.ac'</TT>, and transforms it
into a portable shell script, @command{configure}.
<P>
How does @command{autoconf} perform this task?
<P>
There are two obvious possibilities: creating a brand new language or
extending an existing one. The former option is very attractive: all
sorts of optimizations could easily be implemented in the compiler and
many rigorous checks could be performed on the Autoconf program
(e.g. rejecting any non-portable construct). Alternatively, you can
extend an existing language, such as the <CODE>sh</CODE> (Bourne shell)
language.
<P>
Autoconf does the latter: it is a layer on top of <CODE>sh</CODE>. It was
therefore most convenient to implement @command{autoconf} as a macro
expander: a program that repeatedly performs <EM>macro expansions</EM> on
text input, replacing macro calls with macro bodies and producing a pure
<CODE>sh</CODE> script in the end. Instead of implementing a dedicated
Autoconf macro expander, it is natural to use an existing
general-purpose macro language, such as M4, and implement the extensions
as a set of M4 macros.
<H3><A NAME="SEC9" HREF="autoconf_toc.html#TOC9">The Autoconf Language</A></H3>
<P>
<A NAME="IDX7"></A>
<P>
The Autoconf language is very different from many other computer
languages because it treats actual code the same as plain text. Whereas
in C, for instance, data and instructions have very different syntactic
status, in Autoconf their status is rigorously the same. Therefore, we
need a means to distinguish literal strings from text to be expanded:
quotation.
<P>
When calling macros that take arguments, there must not be any blank
space between the macro name and the open parenthesis. Arguments should
be enclosed within the M4 quote characters <SAMP>`['</SAMP> and <SAMP>`]'</SAMP>, and be
separated by commas. Any leading spaces in arguments are ignored,
unless they are quoted. You may safely leave out the quotes when the
argument is simple text, but <EM>always</EM> quote complex arguments such
as other macro calls. This rule applies recursively for every macro
call, including macros called from other macros.
<P>
For instance:
<PRE>
AC_CHECK_HEADER([stdio.h],
[AC_DEFINE([HAVE_STDIO_H])],
[AC_MSG_ERROR([Sorry, can't do anything for you])])
</PRE>
<P>
is quoted properly. You may safely simplify its quotation to:
<PRE>
AC_CHECK_HEADER(stdio.h,
[AC_DEFINE(HAVE_STDIO_H)],
[AC_MSG_ERROR([Sorry, can't do anything for you])])
</PRE>
<P>
Notice that the argument of <CODE>AC_MSG_ERROR</CODE> is still quoted;
otherwise, its comma would have been interpreted as an argument separator.
<P>
The following example is wrong and dangerous, as it is underquoted:
<PRE>
AC_CHECK_HEADER(stdio.h,
AC_DEFINE(HAVE_STDIO_H),
AC_MSG_ERROR([Sorry, can't do anything for you]))
</PRE>
<P>
In other cases, you may have to use text that also resembles a macro
call. You must quote that text even when it is not passed as a macro
argument:
<PRE>
echo "Hard rock was here! --[AC_DC]"
</PRE>
<P>
which will result in
<PRE>
echo "Hard rock was here! --AC_DC"
</PRE>
<P>
When you use the same text in a macro argument, you must therefore have
an extra quotation level (since one is stripped away by the macro
substitution). In general, then, it is a good idea to <EM>use double
quoting for all literal string arguments</EM>:
<PRE>
AC_MSG_WARN([[AC_DC stinks --Iron Maiden]])
</PRE>
<P>
You are now able to understand one of the constructs of Autoconf that
has been continually misunderstood... The rule of thumb is that
<EM>whenever you expect macro expansion, expect quote expansion</EM>;
i.e., expect one level of quotes to be lost. For instance:
<PRE>
AC_COMPILE_IFELSE([char b[10];],, [AC_MSG_ERROR([you lose])])
</PRE>
<P>
is incorrect: here, the first argument of <CODE>AC_COMPILE_IFELSE</CODE> is
<SAMP>`char b[10];'</SAMP> and will be expanded once, which results in
<SAMP>`char b10;'</SAMP>. (There was an idiom common in Autoconf's past to
address this issue via the M4 <CODE>changequote</CODE> primitive, but do not
use it!) Let's take a closer look: the author meant the first argument
to be understood as a literal, and therefore it must be quoted twice:
<PRE>
AC_COMPILE_IFELSE([[char b[10];]],, [AC_MSG_ERROR([you lose])])
</PRE>
<P>
Voil`a, you actually produce <SAMP>`char b[10];'</SAMP> this time!
<P>
The careful reader will notice that, according to these guidelines, the
"properly" quoted <CODE>AC_CHECK_HEADER</CODE> example above is actually
lacking three pairs of quotes! Nevertheless, for the sake of readability,
double quotation of literals is used only where needed in this manual.
<P>
Some macros take optional arguments, which this documentation represents
as @ovar{arg} (not to be confused with the quote characters). You may
just leave them empty, or use <SAMP>`[]'</SAMP> to make the emptiness of the
argument explicit, or you may simply omit the trailing commas. The
three lines below are equivalent:
<PRE>
AC_CHECK_HEADERS(stdio.h, [], [], [])
AC_CHECK_HEADERS(stdio.h,,,)
AC_CHECK_HEADERS(stdio.h)
</PRE>
<P>
It is best to put each macro call on its own line in
<TT>`configure.ac'</TT>. Most of the macros don't add extra newlines; they
rely on the newline after the macro call to terminate the commands.
This approach makes the generated @command{configure} script a little
easier to read by not inserting lots of blank lines. It is generally
safe to set shell variables on the same line as a macro call, because
the shell allows assignments without intervening newlines.
<P>
You can include comments in <TT>`configure.ac'</TT> files by starting them
with the <SAMP>`#'</SAMP>. For example, it is helpful to begin
<TT>`configure.ac'</TT> files with a line like this:
<PRE>
# Process this file with autoconf to produce a configure script.
</PRE>
<H3><A NAME="SEC10" HREF="autoconf_toc.html#TOC10">Standard <TT>`configure.ac'</TT> Layout</A></H3>
<P>
The order in which <TT>`configure.ac'</TT> calls the Autoconf macros is not
important, with a few exceptions. Every <TT>`configure.ac'</TT> must
contain a call to <CODE>AC_INIT</CODE> before the checks, and a call to
<CODE>AC_OUTPUT</CODE> at the end (see section <A HREF="autoconf.html#SEC19">Outputting Files</A>). Additionally, some macros
rely on other macros having been called first, because they check
previously set values of some variables to decide what to do. These
macros are noted in the individual descriptions (see section <A HREF="autoconf.html#SEC35">Existing Tests</A>), and they also warn you when @command{configure} is created if they
are called out of order.
<P>
To encourage consistency, here is a suggested order for calling the
Autoconf macros. Generally speaking, the things near the end of this
list are those that could depend on things earlier in it. For example,
library functions could be affected by types and libraries.
<PRE>
Autoconf requirements
<CODE>AC_INIT(<VAR>package</VAR>, <VAR>version</VAR>, <VAR>bug-report-address</VAR>)</CODE>
information on the package
checks for programs
checks for libraries
checks for header files
checks for types
checks for structures
checks for compiler characteristics
checks for library functions
checks for system services
<CODE>AC_CONFIG_FILES([<VAR>file...</VAR>])</CODE>
<CODE>AC_OUTPUT</CODE>
</PRE>
<H2><A NAME="SEC11" HREF="autoconf_toc.html#TOC11">Using @command{autoscan} to Create <TT>`configure.ac'</TT></A></H2>
<P>
<A NAME="IDX8"></A>
<P>
The @command{autoscan} program can help you create and/or maintain a
<TT>`configure.ac'</TT> file for a software package. @command{autoscan}
examines source files in the directory tree rooted at a directory given
as a command line argument, or the current directory if none is given.
It searches the source files for common portability problems and creates
a file <TT>`configure.scan'</TT> which is a preliminary <TT>`configure.ac'</TT>
for that package, and checks a possibly existing <TT>`configure.ac'</TT> for
completeness.
<P>
When using @command{autoscan} to create a <TT>`configure.ac'</TT>, you
should manually examine <TT>`configure.scan'</TT> before renaming it to
<TT>`configure.ac'</TT>; it will probably need some adjustments.
Occasionally, @command{autoscan} outputs a macro in the wrong order
relative to another macro, so that @command{autoconf} produces a warning;
you need to move such macros manually. Also, if you want the package to
use a configuration header file, you must add a call to
<CODE>AC_CONFIG_HEADERS</CODE> (see section <A HREF="autoconf.html#SEC27">Configuration Header Files</A>). You might
also have to change or add some <CODE>#if</CODE> directives to your program in
order to make it work with Autoconf (see section <A HREF="autoconf.html#SEC12">Using @command{ifnames} to List Conditionals</A>, for
information about a program that can help with that job).
<P>
When using @command{autoscan} to maintain a <TT>`configure.ac'</TT>, simply
consider adding its suggestions. The file <TT>`autoscan.log'</TT> will
contain detailed information on why a macro is requested.
<P>
@command{autoscan} uses several data files (installed along with Autoconf)
to determine which macros to output when it finds particular symbols in
a package's source files. These data files all have the same format:
each line consists of a symbol, whitespace, and the Autoconf macro to
output if that symbol is encountered. Lines starting with <SAMP>`#'</SAMP> are
comments.
<P>
@command{autoscan} accepts the following options:
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the command line options and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version number of Autoconf and exit.
<DT>@option{--verbose}
<DD>
<DT>@option{-v}
<DD>
Print the names of the files it examines and the potentially interesting
symbols it finds in them. This output can be voluminous.
<DT>@option{--include=<VAR>dir</VAR>}
<DD>
<DT>@option{-I <VAR>dir</VAR>}
<DD>
Also look for input files in <VAR>dir</VAR>. Multiple invocations
accumulate. Directories are browsed from last to first.
</DL>
<H2><A NAME="SEC12" HREF="autoconf_toc.html#TOC12">Using @command{ifnames} to List Conditionals</A></H2>
<P>
<A NAME="IDX9"></A>
<P>
@command{ifnames} can help you write <TT>`configure.ac'</TT> for a software
package. It prints the identifiers that the package already uses in C
preprocessor conditionals. If a package has already been set up to have
some portability, @command{ifnames} can thus help you figure out what its
@command{configure} needs to check for. It may help fill in some gaps in a
<TT>`configure.ac'</TT> generated by @command{autoscan} (see section <A HREF="autoconf.html#SEC11">Using @command{autoscan} to Create @file{configure.ac}</A>).
<P>
@command{ifnames} scans all of the C source files named on the command line
(or the standard input, if none are given) and writes to the standard
output a sorted list of all the identifiers that appear in those files
in <CODE>#if</CODE>, <CODE>#elif</CODE>, <CODE>#ifdef</CODE>, or <CODE>#ifndef</CODE>
directives. It prints each identifier on a line, followed by a
space-separated list of the files in which that identifier occurs.
<P>
@command{ifnames} accepts the following options:
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the command line options and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version number of Autoconf and exit.
</DL>
<H2><A NAME="SEC13" HREF="autoconf_toc.html#TOC13">Using @command{autoconf} to Create @command{configure}</A></H2>
<P>
<A NAME="IDX10"></A>
<P>
To create @command{configure} from <TT>`configure.ac'</TT>, run the
@command{autoconf} program with no arguments. @command{autoconf} processes
<TT>`configure.ac'</TT> with the <CODE>m4</CODE> macro processor, using the
Autoconf macros. If you give @command{autoconf} an argument, it reads that
file instead of <TT>`configure.ac'</TT> and writes the configuration script
to the standard output instead of to @command{configure}. If you give
@command{autoconf} the argument @option{-}, it reads from the standard
input instead of <TT>`configure.ac'</TT> and writes the configuration script
to the standard output.
<P>
The Autoconf macros are defined in several files. Some of the files are
distributed with Autoconf; @command{autoconf} reads them first. Then it
looks for the optional file <TT>`acsite.m4'</TT> in the directory that
contains the distributed Autoconf macro files, and for the optional file
<TT>`aclocal.m4'</TT> in the current directory. Those files can contain
your site's or the package's own Autoconf macro definitions
(see section <A HREF="autoconf.html#SEC101">Writing Autoconf Macros</A>, for more information). If a macro is
defined in more than one of the files that @command{autoconf} reads, the
last definition it reads overrides the earlier ones.
<P>
@command{autoconf} accepts the following options:
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the command line options and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version number of Autoconf and exit.
<DT>@option{--verbose}
<DD>
<DT>@option{-v}
<DD>
Report processing steps.
<DT>@option{--debug}
<DD>
<DT>@option{-d}
<DD>
Don't remove the temporary files.
<DT>@option{--force}
<DD>
<DT>@option{-f}
<DD>
Remake <TT>`configure'</TT> even if newer than its input files.
<DT>@option{--include=<VAR>dir</VAR>}
<DD>
<DT>@option{-I <VAR>dir</VAR>}
<DD>
Also look for input files in <VAR>dir</VAR>. Multiple invocations
accumulate. Directories are browsed from last to first.
<DT>@option{--output=<VAR>file</VAR>}
<DD>
<DT>@option{-o <VAR>file</VAR>}
<DD>
Save output (script or trace) to <VAR>file</VAR>. The file @option{-} stands
for the standard output.
<DT>@option{--warnings=<VAR>category</VAR>}
<DD>
<DT>@option{-W <VAR>category</VAR>}
<DD>
<A NAME="IDX11"></A>
Report the warnings related to <VAR>category</VAR> (which can actually be a
comma separated list). See section <A HREF="autoconf.html#SEC104">Reporting Messages</A>, macro
<CODE>AC_DIAGNOSE</CODE>, for a comprehensive list of categories. Special
values include:
<DL COMPACT>
<DT><SAMP>`all'</SAMP>
<DD>
report all the warnings
<DT><SAMP>`none'</SAMP>
<DD>
report none
<DT><SAMP>`error'</SAMP>
<DD>
treats warnings as errors
<DT><SAMP>`no-<VAR>category</VAR>'</SAMP>
<DD>
disable warnings falling into <VAR>category</VAR>
</DL>
Warnings about <SAMP>`syntax'</SAMP> are enabled by default, and the environment
variable <CODE>WARNINGS</CODE>, a comma separated list of categories, is
honored. @command{autoconf -W <VAR>category</VAR>} will actually
behave as if you had run:
<PRE>
autoconf --warnings=syntax,$WARNINGS,<VAR>category</VAR>
</PRE>
If you want to disable @command{autoconf}'s defaults and <CODE>WARNINGS</CODE>,
but (for example) enable the warnings about obsolete constructs, you
would use @option{-W none,obsolete}.
<A NAME="IDX12"></A>
<A NAME="IDX13"></A>
@command{autoconf} displays a back trace for errors, but not for
warnings; if you want them, just pass @option{-W error}. For instance,
on this <TT>`configure.ac'</TT>:
<PRE>
AC_DEFUN([INNER],
[AC_TRY_RUN([exit (0)])])
AC_DEFUN([OUTER],
[INNER])
AC_INIT
OUTER
</PRE>
you get:
<PRE>
$ <KBD>autoconf -Wcross</KBD>
configure.ac:8: warning: AC_TRY_RUN called without default \
to allow cross compiling
$ <KBD>autoconf -Wcross,error</KBD>
configure.ac:8: error: AC_TRY_RUN called without default \
to allow cross compiling
acgeneral.m4:3044: AC_TRY_RUN is expanded from...
configure.ac:2: INNER is expanded from...
configure.ac:5: OUTER is expanded from...
configure.ac:8: the top level
</PRE>
<DT>@option{--trace=<VAR>macro</VAR>[:<VAR>format</VAR>]}
<DD>
<DT>@option{-t <VAR>macro</VAR>[:<VAR>format</VAR>]}
<DD>
Do not create the @command{configure} script, but list the calls to
<VAR>macro</VAR> according to the <VAR>format</VAR>. Multiple @option{--trace}
arguments can be used to list several macros. Multiple @option{--trace}
arguments for a single macro are not cumulative; instead, you should
just make <VAR>format</VAR> as long as needed.
The <VAR>format</VAR> is a regular string, with newlines if desired, and
several special escape codes. It defaults to <SAMP>`$f:$l:$n:$%'</SAMP>; see
below for details on the <VAR>format</VAR>.
<DT>@option{--initialization}
<DD>
<DT>@option{-i}
<DD>
By default, @option{--trace} does not trace the initialization of the
Autoconf macros (typically the <CODE>AC_DEFUN</CODE> definitions). This
results in a noticeable speedup, but can be disabled by this option.
</DL>
<P>
It is often necessary to check the content of a <TT>`configure.ac'</TT>
file, but parsing it yourself is extremely fragile and error-prone. It
is suggested that you rely upon @option{--trace} to scan
<TT>`configure.ac'</TT>.
<P>
The <VAR>format</VAR> of @option{--trace} can use the following special
escapes:
<DL COMPACT>
<DT><SAMP>`$$'</SAMP>
<DD>
The character <SAMP>`$'</SAMP>.
<DT><SAMP>`$f'</SAMP>
<DD>
The filename from which <VAR>macro</VAR> is called.
<DT><SAMP>`$l'</SAMP>
<DD>
The line number from which <VAR>macro</VAR> is called.
<DT><SAMP>`$d'</SAMP>
<DD>
The depth of the <VAR>macro</VAR> call. This is an M4 technical detail that
you probably don't want to know about.
<DT><SAMP>`$n'</SAMP>
<DD>
The name of the <VAR>macro</VAR>.
<DT><SAMP>`$<VAR>num</VAR>'</SAMP>
<DD>
The <VAR>num</VAR>th argument of the call to <VAR>macro</VAR>.
<DT><SAMP>`$@'</SAMP>
<DD>
<DT><SAMP>`$<VAR>sep</VAR>@'</SAMP>
<DD>
<DT><SAMP>`${<VAR>separator</VAR>}@'</SAMP>
<DD>
All the arguments passed to <VAR>macro</VAR>, separated by the character
<VAR>sep</VAR> or the string <VAR>separator</VAR> (<SAMP>`,'</SAMP> by default). Each
argument is quoted, i.e. enclosed in a pair of square brackets.
<DT><SAMP>`$*'</SAMP>
<DD>
<DT><SAMP>`$<VAR>sep</VAR>*'</SAMP>
<DD>
<DT><SAMP>`${<VAR>separator</VAR>}*'</SAMP>
<DD>
As above, but the arguments are not quoted.
<DT><SAMP>`$%'</SAMP>
<DD>
<DT><SAMP>`$<VAR>sep</VAR>%'</SAMP>
<DD>
<DT><SAMP>`${<VAR>separator</VAR>}%'</SAMP>
<DD>
As above, but the arguments are not quoted, all new line characters in
the arguments are smashed, and the default separator is <SAMP>`:'</SAMP>.
The escape <SAMP>`$%'</SAMP> produces single-line trace outputs (unless you put
newlines in the <SAMP>`separator'</SAMP>), while <SAMP>`$@'</SAMP> and <SAMP>`$*'</SAMP> do
not.
</DL>
<P>
For instance, to find the list of variables that are substituted, use:
<PRE>
$ <KBD>autoconf -t AC_SUBST</KBD>
configure.ac:2:AC_SUBST:ECHO_C
configure.ac:2:AC_SUBST:ECHO_N
configure.ac:2:AC_SUBST:ECHO_T
<I>More traces deleted</I>
</PRE>
<P>
The example below highlights the difference between <SAMP>`$@'</SAMP>,
<SAMP>`$*'</SAMP>, and <STRONG>$%</STRONG>.
<PRE>
$ <KBD>cat configure.ac</KBD>
AC_DEFINE(This, is, [an
[example]])
$ <KBD>autoconf -t 'AC_DEFINE:@: $@</KBD>
*: $*
$: $%'
@: [This],[is],[an
[example]]
*: This,is,an
[example]
$: This:is:an [example]
</PRE>
<P>
The <VAR>format</VAR> gives you a lot of freedom:
<PRE>
$ <KBD>autoconf -t 'AC_SUBST:$$ac_subst{"$1"} = "$f:$l";'</KBD>
$ac_subst{"ECHO_C"} = "configure.ac:2";
$ac_subst{"ECHO_N"} = "configure.ac:2";
$ac_subst{"ECHO_T"} = "configure.ac:2";
<I>More traces deleted</I>
</PRE>
<P>
A long <VAR>separator</VAR> can be used to improve the readability of complex
structures, and to ease its parsing (for instance when no single
character is suitable as a separator)):
<PRE>
$ <KBD>autoconf -t 'AM_MISSING_PROG:${|:::::|}*'</KBD>
ACLOCAL|:::::|aclocal|:::::|$missing_dir
AUTOCONF|:::::|autoconf|:::::|$missing_dir
AUTOMAKE|:::::|automake|:::::|$missing_dir
<I>More traces deleted</I>
</PRE>
<H2><A NAME="SEC14" HREF="autoconf_toc.html#TOC14">Using @command{autoreconf} to Update @command{configure} Scripts</A></H2>
<P>
<A NAME="IDX14"></A>
<P>
Installing the various components of the GNU Build System can be
tedious: running @command{gettextize}, @command{automake} etc. in each
directory. It may be needed either because some tools such as
@command{automake} have been updated on your system, or because some of
the sources such as <TT>`configure.ac'</TT> have been updated, or finally,
simply in order to install the GNU Build System in a fresh tree.
<P>
It runs @command{autoconf}, @command{autoheader}, @command{aclocal},
@command{automake}, @command{libtoolize}, and @command{gettextize} (when
appropriate) repeatedly to update the GNU Build System in specified
directories, and their subdirectories (see section <A HREF="autoconf.html#SEC33">Configuring Other Packages in Subdirectories</A>). By
default, it only remakes those files that are older than their sources.
<P>
If you install a new version of some tools, you can make
@command{autoreconf} remake <EM>all</EM> of the files by giving it the
@option{--force} option.
<P>
See section <A HREF="autoconf.html#SEC26">Automatic Remaking</A>, for <TT>`Makefile'</TT> rules to automatically
remake @command{configure} scripts when their source files change. That
method handles the timestamps of configuration header templates
properly, but does not pass @option{--autoconf-dir=<VAR>dir</VAR>} or
@option{--localdir=<VAR>dir</VAR>}.
<P>
@command{autoreconf} accepts the following options:
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the command line options and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version number of Autoconf and exit.
<DT>@option{--verbose}
<DD>
Print the name of each directory where @command{autoreconf} runs
@command{autoconf} (and @command{autoheader}, if appropriate).
<DT>@option{--debug}
<DD>
<DT>@option{-d}
<DD>
Don't remove the temporary files.
<DT>@option{--force}
<DD>
<DT>@option{-f}
<DD>
Remake even <TT>`configure'</TT> scripts and configuration headers that are
newer than their input files (<TT>`configure.ac'</TT> and, if present,
<TT>`aclocal.m4'</TT>).
<DT>@option{--install}
<DD>
<DT>@option{-i}
<DD>
Copy missing auxiliary files. This option is similar to the option
<CODE>--add-missing</CODE> in @command{automake}.
<DT>@option{--symlink}
<DD>
<DT>@option{-s}
<DD>
Instead of copying missing auxiliary files, install symbolic links.
<DT>@option{--include=<VAR>dir</VAR>}
<DD>
<DT>@option{-I <VAR>dir</VAR>}
<DD>
Also look for input files in <VAR>dir</VAR>. Multiple invocations
accumulate. Directories are browsed from last to first.
</DL>
<H1><A NAME="SEC15" HREF="autoconf_toc.html#TOC15">Initialization and Output Files</A></H1>
<P>
Autoconf-generated @command{configure} scripts need some information about
how to initialize, such as how to find the package's source files; and
about the output files to produce. The following sections describe
initialization and the creation of output files.
<H2><A NAME="SEC16" HREF="autoconf_toc.html#TOC16">Initializing @command{configure}</A></H2>
<P>
Every @command{configure} script must call <CODE>AC_INIT</CODE> before doing
anything else. The only other required macro is <CODE>AC_OUTPUT</CODE>
(see section <A HREF="autoconf.html#SEC19">Outputting Files</A>).
<P>
<DL>
<DT><U>Macro:</U> <B>AC_INIT</B> <I>(<VAR>package</VAR>, <VAR>version</VAR>, @ovar{bug-report}, @ovar{tarname})</I>
<DD><A NAME="IDX15"></A>
<A NAME="IDX16"></A>
Process any command-line arguments and perform various initializations
and verifications.
<P>
Set the name of the <VAR>package</VAR> and its <VAR>version</VAR>. These are
typically used in @option{--version} support, including that of
@command{configure}. The optional argument <VAR>bug-report</VAR> should be
the email to which users should send bug reports. The package
<VAR>tarname</VAR> differs from <VAR>package</VAR>: the latter designates the full
package name (e.g., <SAMP>`GNU Autoconf'</SAMP>), while the latter is meant for
distribution tar ball names (e.g., <SAMP>`autoconf'</SAMP>). It defaults to
<VAR>package</VAR> once <SAMP>`GNU '</SAMP> strip, lower cased, and all non
alphanumeric character mapped onto <SAMP>`-'</SAMP>.
<P>
It is preferable that these arguments be static, i.e., there should not
be any shell computation, but they can be computed by M4. The following
M4 macros (e.g., <CODE>AC_PACKAGE_NAME</CODE>), output variables (e.g.,
<CODE>PACKAGE_NAME</CODE>), and preprocessor symbols (e.g.,
<CODE>PACKAGE_NAME</CODE>) are then defined:
<DL COMPACT>
<DT><CODE>AC_PACKAGE_NAME</CODE>, <CODE>PACKAGE_NAME</CODE>
<DD>
<A NAME="IDX17"></A>
<A NAME="IDX18"></A>
<A NAME="IDX19"></A>
Exactly <VAR>package</VAR>.
<DT><CODE>AC_PACKAGE_TARNAME</CODE>, <CODE>PACKAGE_TARNAME</CODE>
<DD>
<A NAME="IDX20"></A>
<A NAME="IDX21"></A>
<A NAME="IDX22"></A>
Exactly <VAR>tarname</VAR>.
<DT><CODE>AC_PACKAGE_VERSION</CODE>, <CODE>PACKAGE_VERSION</CODE>
<DD>
<A NAME="IDX23"></A>
<A NAME="IDX24"></A>
<A NAME="IDX25"></A>
Exactly <VAR>version</VAR>.
<DT><CODE>AC_PACKAGE_STRING</CODE>, <CODE>PACKAGE_STRING</CODE>
<DD>
<A NAME="IDX26"></A>
<A NAME="IDX27"></A>
<A NAME="IDX28"></A>
Exactly <SAMP>`<VAR>package</VAR> <VAR>version</VAR>'</SAMP>.
<DT><CODE>AC_PACKAGE_BUGREPORT</CODE>, <CODE>PACKAGE_BUGREPORT</CODE>
<DD>
<A NAME="IDX29"></A>
<A NAME="IDX30"></A>
<A NAME="IDX31"></A>
Exactly <VAR>bug-report</VAR>.
</DL>
</DL>
<H2><A NAME="SEC17" HREF="autoconf_toc.html#TOC17">Notices in @command{configure}</A></H2>
<P>
The following macros manage version numbers for @command{configure}
scripts. Using them is optional.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PREREQ</B> <I>(<VAR>version</VAR>)</I>
<DD><A NAME="IDX32"></A>
<A NAME="IDX33"></A>
<A NAME="IDX34"></A>
Ensure that a recent enough version of Autoconf is being used. If the
version of Autoconf being used to create @command{configure} is earlier
than <VAR>version</VAR>, print an error message to the standard error output
and do not create @command{configure}. For example:
<PRE>
AC_PREREQ(2.53)
</PRE>
<P>
This macro is the only macro that may be used before <CODE>AC_INIT</CODE>, but
for consistency, you are invited not to do so.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_COPYRIGHT</B> <I>(<VAR>copyright-notice</VAR>)</I>
<DD><A NAME="IDX35"></A>
<A NAME="IDX36"></A>
<A NAME="IDX37"></A>
State that, in addition to the Free Software Foundation's copyright on
the Autoconf macros, parts of your @command{configure} are covered by the
<VAR>copyright-notice</VAR>.
<P>
The <VAR>copyright-notice</VAR> will show up in both the head of
@command{configure} and in <SAMP>`configure --version'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_REVISION</B> <I>(<VAR>revision-info</VAR>)</I>
<DD><A NAME="IDX38"></A>
<A NAME="IDX39"></A>
<A NAME="IDX40"></A>
Copy revision stamp <VAR>revision-info</VAR> into the @command{configure}
script, with any dollar signs or double-quotes removed. This macro lets
you put a revision stamp from <TT>`configure.ac'</TT> into @command{configure}
without RCS or <CODE>cvs</CODE> changing it when you check in
@command{configure}. That way, you can determine easily which revision of
<TT>`configure.ac'</TT> a particular @command{configure} corresponds to.
<P>
For example, this line in <TT>`configure.ac'</TT>:
<PRE>
AC_REVISION($Revision: 1.1 $)
</PRE>
<P>
produces this in @command{configure}:
<PRE>
#! /bin/sh
# From configure.ac Revision: 1.30
</PRE>
</DL>
<H2><A NAME="SEC18" HREF="autoconf_toc.html#TOC18">Finding @command{configure} Input</A></H2>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_SRCDIR</B> <I>(<VAR>unique-file-in-source-dir</VAR>)</I>
<DD><A NAME="IDX41"></A>
<A NAME="IDX42"></A>
<VAR>unique-file-in-source-dir</VAR> is some file that is in the package's
source directory; @command{configure} checks for this file's existence to
make sure that the directory that it is told contains the source code in
fact does. Occasionally people accidentally specify the wrong directory
with @option{--srcdir}; this is a safety check. See section <A HREF="autoconf.html#SEC144">@command{configure} Invocation</A>, for more information.
</DL>
<P>
Packages that do manual configuration or use the <CODE>install</CODE> program
might need to tell @command{configure} where to find some other shell
scripts by calling <CODE>AC_CONFIG_AUX_DIR</CODE>, though the default places
it looks are correct for most cases.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_AUX_DIR</B> <I>(<VAR>dir</VAR>)</I>
<DD><A NAME="IDX43"></A>
<A NAME="IDX44"></A>
Use the auxiliary build tools (e.g., <TT>`install-sh'</TT>,
<TT>`config.sub'</TT>, <TT>`config.guess'</TT>, Cygnus @command{configure},
Automake and Libtool scripts etc.) that are in directory <VAR>dir</VAR>.
These are auxiliary files used in configuration. <VAR>dir</VAR> can be
either absolute or relative to <TT>`<VAR>srcdir</VAR>'</TT>. The default is
<TT>`<VAR>srcdir</VAR>'</TT> or <TT>`<VAR>srcdir</VAR>/..'</TT> or
<TT>`<VAR>srcdir</VAR>/../..'</TT>, whichever is the first that contains
<TT>`install-sh'</TT>. The other files are not checked for, so that using
<CODE>AC_PROG_INSTALL</CODE> does not automatically require distributing the
other auxiliary files. It checks for <TT>`install.sh'</TT> also, but that
name is obsolete because some @command{make} have a rule that creates
<TT>`install'</TT> from it if there is no <TT>`Makefile'</TT>.
</DL>
<H2><A NAME="SEC19" HREF="autoconf_toc.html#TOC19">Outputting Files</A></H2>
<P>
Every Autoconf script, e.g., <TT>`configure.ac'</TT>, should finish by
calling <CODE>AC_OUTPUT</CODE>. It is the macro that generates
<TT>`config.status'</TT>, which will create the <TT>`Makefile'</TT>s and any
other files resulting from configuration. The only required macro is
<CODE>AC_INIT</CODE> (see section <A HREF="autoconf.html#SEC18">Finding @command{configure} Input</A>).
<P>
<DL>
<DT><U>Macro:</U> <B>AC_OUTPUT</B>
<DD><A NAME="IDX45"></A>
<A NAME="IDX46"></A>
<A NAME="IDX47"></A>
Generate <TT>`config.status'</TT> and launch it. Call this macro once, at
the end of <TT>`configure.ac'</TT>.
<P>
<TT>`config.status'</TT> will take all the configuration actions: all the
output files (see section <A HREF="autoconf.html#SEC21">Creating Configuration Files</A>, macro
<CODE>AC_CONFIG_FILES</CODE>), header files (see section <A HREF="autoconf.html#SEC27">Configuration Header Files</A>,
macro <CODE>AC_CONFIG_HEADERS</CODE>), commands (see section <A HREF="autoconf.html#SEC31">Running Arbitrary Configuration Commands</A>, macro <CODE>AC_CONFIG_COMMANDS</CODE>), links (see
section <A HREF="autoconf.html#SEC32">Creating Configuration Links</A>, macro <CODE>AC_CONFIG_LINKS</CODE>), subdirectories
to configure (see section <A HREF="autoconf.html#SEC33">Configuring Other Packages in Subdirectories</A>, macro <CODE>AC_CONFIG_SUBDIRS</CODE>)
are honored.
</DL>
<P>
Historically, the usage of <CODE>AC_OUTPUT</CODE> was somewhat different.
See section <A HREF="autoconf.html#SEC150">Obsolete Macros</A>, for a description of the arguments that
<CODE>AC_OUTPUT</CODE> used to support.
<P>
If you run <CODE>make</CODE> on subdirectories, you should run it using the
<CODE>make</CODE> variable <CODE>MAKE</CODE>. Most versions of <CODE>make</CODE> set
<CODE>MAKE</CODE> to the name of the <CODE>make</CODE> program plus any options it
was given. (But many do not include in it the values of any variables
set on the command line, so those are not passed on automatically.)
Some old versions of <CODE>make</CODE> do not set this variable. The
following macro allows you to use it even with those versions.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_MAKE_SET</B>
<DD><A NAME="IDX48"></A>
<A NAME="IDX49"></A>
<A NAME="IDX50"></A>
If <CODE>make</CODE> predefines the variable <CODE>MAKE</CODE>, define output
variable <CODE>SET_MAKE</CODE> to be empty. Otherwise, define <CODE>SET_MAKE</CODE>
to contain <SAMP>`MAKE=make'</SAMP>. Calls <CODE>AC_SUBST</CODE> for <CODE>SET_MAKE</CODE>.
</DL>
<P>
To use this macro, place a line like this in each <TT>`Makefile.in'</TT>
that runs <CODE>MAKE</CODE> on other directories:
<PRE>
@SET_MAKE@
</PRE>
<H2><A NAME="SEC20" HREF="autoconf_toc.html#TOC20">Taking Configuration Actions</A></H2>
<P>
<TT>`configure'</TT> is designed so that it appears to do everything itself,
but there is actually a hidden slave: <TT>`config.status'</TT>.
<TT>`configure'</TT> is in charge of examining your system, but it is
<TT>`config.status'</TT> that actually takes the proper actions based on the
results of <TT>`configure'</TT>. The most typical task of
<TT>`config.status'</TT> is to <EM>instantiate</EM> files.
<P>
This section describes the common behavior of the four standard
instantiating macros: <CODE>AC_CONFIG_FILES</CODE>, <CODE>AC_CONFIG_HEADERS</CODE>,
<CODE>AC_CONFIG_COMMANDS</CODE> and <CODE>AC_CONFIG_LINKS</CODE>. They all
have this prototype:
<PRE>
AC_CONFIG_FOOS(<VAR>tag</VAR>..., [<VAR>commands</VAR>], [<VAR>init-cmds</VAR>])
</PRE>
<P>
where the arguments are:
<DL COMPACT>
<DT><VAR><VAR>tag</VAR>...</VAR>
<DD>
A whitespace-separated list of tags, which are typically the names of
the files to instantiate.
You are encouraged to use literals as <VAR>tags</VAR>. In particular, you
should avoid
<PRE>
... && my_foos="$my_foos fooo"
... && my_foos="$my_foos foooo"
AC_CONFIG_FOOS($my_foos)
</PRE>
and use this instead:
<PRE>
... && AC_CONFIG_FOOS(fooo)
... && AC_CONFIG_FOOS(foooo)
</PRE>
The macros <CODE>AC_CONFIG_FILES</CODE> and <CODE>AC_CONFIG_HEADERS</CODE> use
special <VAR>tag</VAR>s: they may have the form <SAMP>`<VAR>output</VAR>'</SAMP> or
<SAMP>`<VAR>output</VAR>:<VAR>inputs</VAR>'</SAMP>. The file <VAR>output</VAR> is instantiated
from its templates, <VAR>inputs</VAR> (defaulting to <SAMP>`<VAR>output</VAR>.in'</SAMP>).
For instance
<SAMP>`AC_CONFIG_FILES(Makefile:boiler/top.mk:boiler/bot.mk)'</SAMP> asks for
the creation of <TT>`Makefile'</TT> that will be the expansion of the
output variables in the concatenation of <TT>`boiler/top.mk'</TT> and
<TT>`boiler/bot.mk'</TT>.
The special value <SAMP>`-'</SAMP> might be used to denote the standard output
when used in <VAR>output</VAR>, or the standard input when used in the
<VAR>inputs</VAR>. You most probably don't need to use this in
<TT>`configure.ac'</TT>, but it is convenient when using the command line
interface of <TT>`./config.status'</TT>, see section <A HREF="autoconf.html#SEC145">Recreating a Configuration</A>,
for more details.
The <VAR>inputs</VAR> may be absolute or relative filenames. In the latter
case they are first looked for in the build tree, and then in the source
tree.
<DT><VAR>commands</VAR>
<DD>
Shell commands output literally into <TT>`config.status'</TT>, and
associated with a tag that the user can use to tell <TT>`config.status'</TT>
which the commands to run. The commands are run each time a <VAR>tag</VAR>
request is given to <TT>`config.status'</TT>; typically, each time the file
<TT>`<VAR>tag</VAR>'</TT> is created.
The variable set during the execution of @command{configure} are
<EM>not</EM> available here: you first need to set them via the
<VAR>init-cmds</VAR>. Nonetheless the following variables are precomputed:
<DL COMPACT>
<DT><CODE>srcdir</CODE>
<DD>
The path from the top build directory to the top source directory. This
is what @command{configure}'s option @option{--srcdir} sets.
<DT><CODE>ac_top_srcdir</CODE>
<DD>
The path from the current build directory to the top source directory.
<DT><CODE>ac_top_builddir</CODE>
<DD>
The path from the current build directory to the top build directory.
It can be empty, or else ends with a slash, so that you may concatenate
it.
<DT><CODE>ac_srcdir</CODE>
<DD>
The path from the current build directory to the corresponding source
directory.
</DL>
The <EM>current</EM> directory refers to the directory (or
pseudo-directory) containing the input part of <VAR>tags</VAR>. For
instance, running
<PRE>
AC_CONFIG_COMMANDS([deep/dir/out:in/in.in], [...], [...])
</PRE>
with @option{--srcdir=../package} produces the following values:
<PRE>
# Argument of --srcdir
srcdir='../package'
# Reversing deep/dir
ac_top_builddir='../../'
# Concatenation of $ac_top_builddir and srcdir
ac_top_srcdir='../../../package'
# Concatenation of $ac_top_srcdir and deep/dir
ac_srcdir='../../../package/deep/dir'
</PRE>
independently of <SAMP>`in/in.in'</SAMP>.
<DT><VAR>init-cmds</VAR>
<DD>
Shell commands output <EM>unquoted</EM> near the beginning of
<TT>`config.status'</TT>, and executed each time <TT>`config.status'</TT> runs
(regardless of the tag). Because they are unquoted, for example,
<SAMP>`$var'</SAMP> will be output as the value of <CODE>var</CODE>. <VAR>init-cmds</VAR>
is typically used by <TT>`configure'</TT> to give <TT>`config.status'</TT> some
variables it needs to run the <VAR>commands</VAR>.
You should be extremely cautious in your variable names: all the
<VAR>init-cmds</VAR> share the same name space and may overwrite each other
in unpredictable ways. Sorry...
</DL>
<P>
All these macros can be called multiple times, with different
<VAR>tag</VAR>s, of course!
<H2><A NAME="SEC21" HREF="autoconf_toc.html#TOC21">Creating Configuration Files</A></H2>
<P>
Be sure to read the previous section, section <A HREF="autoconf.html#SEC20">Taking Configuration Actions</A>.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_FILES</B> <I>(<VAR>file</VAR>..., @ovar{cmds}, @ovar{init-cmds})</I>
<DD><A NAME="IDX51"></A>
<A NAME="IDX52"></A>
Make <CODE>AC_OUTPUT</CODE> create each <TT>`<VAR>file</VAR>'</TT> by copying an input
file (by default <TT>`<VAR>file</VAR>.in'</TT>), substituting the output variable
values.
This macro is one of the instantiating macros, see section <A HREF="autoconf.html#SEC20">Taking Configuration Actions</A>. See section <A HREF="autoconf.html#SEC22">Substitutions in Makefiles</A>, for more information on using
output variables. See section <A HREF="autoconf.html#SEC81">Setting Output Variables</A>, for more information
on creating them. This macro creates the directory that the file is in
if it doesn't exist. Usually, <TT>`Makefile'</TT>s are created this way,
but other files, such as <TT>`.gdbinit'</TT>, can be specified as well.
<P>
Typical calls to <CODE>AC_CONFIG_FILES</CODE> look like this:
<PRE>
AC_CONFIG_FILES([Makefile src/Makefile man/Makefile X/Imakefile])
AC_CONFIG_FILES([autoconf], [chmod +x autoconf])
</PRE>
<P>
You can override an input file name by appending to <VAR>file</VAR> a
colon-separated list of input files. Examples:
<PRE>
AC_CONFIG_FILES([Makefile:boiler/top.mk:boiler/bot.mk]
[lib/Makefile:boiler/lib.mk])
</PRE>
<P>
Doing this allows you to keep your file names acceptable to MS-DOS, or
to prepend and/or append boilerplate to the file.
</DL>
<H2><A NAME="SEC22" HREF="autoconf_toc.html#TOC22">Substitutions in Makefiles</A></H2>
<P>
Each subdirectory in a distribution that contains something to be
compiled or installed should come with a file <TT>`Makefile.in'</TT>, from
which @command{configure} will create a <TT>`Makefile'</TT> in that directory.
To create a <TT>`Makefile'</TT>, @command{configure} performs a simple variable
substitution, replacing occurrences of <SAMP>`@<VAR>variable</VAR>@'</SAMP> in
<TT>`Makefile.in'</TT> with the value that @command{configure} has determined
for that variable. Variables that are substituted into output files in
this way are called <EM>output variables</EM>. They are ordinary shell
variables that are set in @command{configure}. To make @command{configure}
substitute a particular variable into the output files, the macro
<CODE>AC_SUBST</CODE> must be called with that variable name as an argument.
Any occurrences of <SAMP>`@<VAR>variable</VAR>@'</SAMP> for other variables are
left unchanged. See section <A HREF="autoconf.html#SEC81">Setting Output Variables</A>, for more information
on creating output variables with <CODE>AC_SUBST</CODE>.
<P>
A software package that uses a @command{configure} script should be
distributed with a file <TT>`Makefile.in'</TT>, but no <TT>`Makefile'</TT>; that
way, the user has to properly configure the package for the local system
before compiling it.
<P>
See section `Makefile Conventions' in <CITE>The GNU Coding Standards</CITE>, for more information on what to put in
<TT>`Makefile'</TT>s.
<H3><A NAME="SEC23" HREF="autoconf_toc.html#TOC23">Preset Output Variables</A></H3>
<P>
Some output variables are preset by the Autoconf macros. Some of the
Autoconf macros set additional output variables, which are mentioned in
the descriptions for those macros. See section <A HREF="autoconf.html#SEC185">Output Variable Index</A>, for a
complete list of output variables. See section <A HREF="autoconf.html#SEC24">Installation Directory Variables</A>, for the list of the preset ones related to installation
directories. Below are listed the other preset ones. They all are
precious variables (see section <A HREF="autoconf.html#SEC81">Setting Output Variables</A>,
<CODE>AC_ARG_VAR</CODE>).
<P>
<DL>
<DT><U>Variable:</U> <B>CFLAGS</B>
<DD><A NAME="IDX53"></A>
<A NAME="IDX54"></A>
Debugging and optimization options for the C compiler. If it is not set
in the environment when @command{configure} runs, the default value is set
when you call <CODE>AC_PROG_CC</CODE> (or empty if you don't). @command{configure}
uses this variable when compiling programs to test for C features.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>configure_input</B>
<DD><A NAME="IDX55"></A>
<A NAME="IDX56"></A>
A comment saying that the file was generated automatically by
@command{configure} and giving the name of the input file.
<CODE>AC_OUTPUT</CODE> adds a comment line containing this variable to the top
of every <TT>`Makefile'</TT> it creates. For other files, you should
reference this variable in a comment at the top of each input file. For
example, an input shell script should begin like this:
<PRE>
#! /bin/sh
# @configure_input@
</PRE>
<P>
The presence of that line also reminds people editing the file that it
needs to be processed by @command{configure} in order to be used.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>CPPFLAGS</B>
<DD><A NAME="IDX57"></A>
<A NAME="IDX58"></A>
Header file search directory (@option{-I<VAR>dir</VAR>}) and any other
miscellaneous options for the C and C++ preprocessors and compilers. If
it is not set in the environment when @command{configure} runs, the default
value is empty. @command{configure} uses this variable when compiling or
preprocessing programs to test for C and C++ features.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>CXXFLAGS</B>
<DD><A NAME="IDX59"></A>
<A NAME="IDX60"></A>
Debugging and optimization options for the C++ compiler. If it is not
set in the environment when @command{configure} runs, the default value is
set when you call <CODE>AC_PROG_CXX</CODE> (or empty if you don't).
@command{configure} uses this variable when compiling programs to test for
C++ features.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>DEFS</B>
<DD><A NAME="IDX61"></A>
<A NAME="IDX62"></A>
@option{-D} options to pass to the C compiler. If <CODE>AC_CONFIG_HEADERS</CODE>
is called, @command{configure} replaces <SAMP>`@DEFS@'</SAMP> with
@option{-DHAVE_CONFIG_H} instead (see section <A HREF="autoconf.html#SEC27">Configuration Header Files</A>). This
variable is not defined while @command{configure} is performing its tests,
only when creating the output files. See section <A HREF="autoconf.html#SEC81">Setting Output Variables</A>, for
how to check the results of previous tests.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>ECHO_C</B>
<DD><A NAME="IDX63"></A>
<DT><U>Variable:</U> <B>ECHO_N</B>
<DD><A NAME="IDX64"></A>
<DT><U>Variable:</U> <B>ECHO_T</B>
<DD><A NAME="IDX65"></A>
<A NAME="IDX66"></A>
<A NAME="IDX67"></A>
<A NAME="IDX68"></A>
How does one suppress the trailing newline from <CODE>echo</CODE> for
question-answer message pairs? These variables provide a way:
<PRE>
echo $ECHO_N "And the winner is... $ECHO_C"
sleep 100000000000
echo "${ECHO_T}dead."
</PRE>
<P>
Some old and uncommon <CODE>echo</CODE> implementations offer no means to
achieve this, in which case <CODE>ECHO_T</CODE> is set to tab. You might not
want to use it.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>FFLAGS</B>
<DD><A NAME="IDX69"></A>
<A NAME="IDX70"></A>
Debugging and optimization options for the Fortran 77 compiler. If it
is not set in the environment when @command{configure} runs, the default
value is set when you call <CODE>AC_PROG_F77</CODE> (or empty if you don't).
@command{configure} uses this variable when compiling programs to test for
Fortran 77 features.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>LDFLAGS</B>
<DD><A NAME="IDX71"></A>
<A NAME="IDX72"></A>
Stripping (@option{-s}), path (@option{-L}), and any other miscellaneous
options for the linker. Don't use this variable to pass library names
(@option{-l}) to the linker, use <CODE>LIBS</CODE> instead. If it is not set
in the environment when @command{configure} runs, the default value is empty.
@command{configure} uses this variable when linking programs to test for
C, C++ and Fortran 77 features.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>LIBS</B>
<DD><A NAME="IDX73"></A>
<A NAME="IDX74"></A>
@option{-l} options to pass to the linker. The default value is empty,
but some Autoconf macros may prepend extra libraries to this variable if
those libraries are found and provide necessary functions, see
section <A HREF="autoconf.html#SEC43">Library Files</A>. @command{configure} uses this variable when linking
programs to test for C, C++ and Fortran 77 features.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>builddir</B>
<DD><A NAME="IDX75"></A>
<A NAME="IDX76"></A>
Rigorously equal to <SAMP>`.'</SAMP>. Added for symmetry only.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>abs_builddir</B>
<DD><A NAME="IDX77"></A>
<A NAME="IDX78"></A>
Absolute path of <CODE>builddir</CODE>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>top_builddir</B>
<DD><A NAME="IDX79"></A>
<A NAME="IDX80"></A>
The relative path to the top-level of the current build tree. In the
top-level directory, this is the same as <CODE>srcbuild</CODE>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>abs_top_builddir</B>
<DD><A NAME="IDX81"></A>
<A NAME="IDX82"></A>
Absolute path of <CODE>top_builddir</CODE>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>srcdir</B>
<DD><A NAME="IDX83"></A>
<A NAME="IDX84"></A>
The relative path to the directory that contains the source code for
that <TT>`Makefile'</TT>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>abs_srcdir</B>
<DD><A NAME="IDX85"></A>
<A NAME="IDX86"></A>
Absolute path of <CODE>srcdir</CODE>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>top_srcdir</B>
<DD><A NAME="IDX87"></A>
<A NAME="IDX88"></A>
The relative path to the top-level source code directory for the
package. In the top-level directory, this is the same as <CODE>srcdir</CODE>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>abs_top_srcdir</B>
<DD><A NAME="IDX89"></A>
<A NAME="IDX90"></A>
Absolute path of <CODE>top_srcdir</CODE>.
</DL>
<H3><A NAME="SEC24" HREF="autoconf_toc.html#TOC24">Installation Directory Variables</A></H3>
<P>
The following variables specify the directories where the package will
be installed, see section `Variables for Installation Directories' in <CITE>The GNU Coding Standards</CITE>, for more information.
See the end of this section for details on when and how to use these
variables.
<P>
<DL>
<DT><U>Variable:</U> <B>bindir</B>
<DD><A NAME="IDX91"></A>
<A NAME="IDX92"></A>
The directory for installing executables that users run.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>datadir</B>
<DD><A NAME="IDX93"></A>
<A NAME="IDX94"></A>
The directory for installing read-only architecture-independent data.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>exec_prefix</B>
<DD><A NAME="IDX95"></A>
<A NAME="IDX96"></A>
The installation prefix for architecture-dependent files. By default
it's the same as <VAR>prefix</VAR>. You should avoid installing anything
directly to <VAR>exec_prefix</VAR>. However, the default value for
directories containing architecture-dependent files should be relative
to <VAR>exec_prefix</VAR>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>includedir</B>
<DD><A NAME="IDX97"></A>
<A NAME="IDX98"></A>
The directory for installing C header files.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>infodir</B>
<DD><A NAME="IDX99"></A>
<A NAME="IDX100"></A>
The directory for installing documentation in Info format.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>libdir</B>
<DD><A NAME="IDX101"></A>
<A NAME="IDX102"></A>
The directory for installing object code libraries.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>libexecdir</B>
<DD><A NAME="IDX103"></A>
<A NAME="IDX104"></A>
The directory for installing executables that other programs run.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>localstatedir</B>
<DD><A NAME="IDX105"></A>
<A NAME="IDX106"></A>
The directory for installing modifiable single-machine data.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>mandir</B>
<DD><A NAME="IDX107"></A>
<A NAME="IDX108"></A>
The top-level directory for installing documentation in man format.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>oldincludedir</B>
<DD><A NAME="IDX109"></A>
<A NAME="IDX110"></A>
The directory for installing C header files for non-gcc compilers.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>prefix</B>
<DD><A NAME="IDX111"></A>
<A NAME="IDX112"></A>
The common installation prefix for all files. If <VAR>exec_prefix</VAR>
is defined to a different value, <VAR>prefix</VAR> is used only for
architecture-independent files.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>sbindir</B>
<DD><A NAME="IDX113"></A>
<A NAME="IDX114"></A>
The directory for installing executables that system
administrators run.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>sharedstatedir</B>
<DD><A NAME="IDX115"></A>
<A NAME="IDX116"></A>
The directory for installing modifiable architecture-independent data.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>sysconfdir</B>
<DD><A NAME="IDX117"></A>
<A NAME="IDX118"></A>
The directory for installing read-only single-machine data.
</DL>
<P>
Most of these variables have values that rely on <CODE>prefix</CODE> or
<CODE>exec_prefix</CODE>. It is deliberate that the directory output
variables keep them unexpanded: typically <SAMP>`@datadir@'</SAMP> will be
replaced by <SAMP>`${prefix}/share'</SAMP>, not <SAMP>`/usr/local/share'</SAMP>.
<P>
This behavior is mandated by the GNU coding standards, so that when
the user runs:
<DL COMPACT>
<DT><SAMP>`make'</SAMP>
<DD>
she can still specify a different prefix from the one specified to
@command{configure}, in which case, if needed, the package shall hard
code dependencies corresponding to the make-specified prefix.
<DT><SAMP>`make install'</SAMP>
<DD>
she can specify a different installation location, in which case the
package <EM>must</EM> still depend on the location which was compiled in
(i.e., never recompile when <SAMP>`make install'</SAMP> is run). This is an
extremely important feature, as many people may decide to install all
the files of a package grouped together, and then install links from
the final locations to there.
</DL>
<P>
In order to support these features, it is essential that <CODE>datadir</CODE>
remains being defined as <SAMP>`${prefix}/share'</SAMP> to depend upon the
current value of <CODE>prefix</CODE>.
<P>
A corollary is that you should not use these variables except in
Makefiles. For instance, instead of trying to evaluate <CODE>datadir</CODE>
in <TT>`configure'</TT> and hardcoding it in Makefiles using
e.g. <SAMP>`AC_DEFINE_UNQUOTED(DATADIR, "$datadir")'</SAMP>, you should add
<SAMP>`-DDATADIR="$(datadir)"'</SAMP> to your <CODE>CPPFLAGS</CODE>.
<P>
Similarly you should not rely on <CODE>AC_OUTPUT_FILES</CODE> to replace
<CODE>datadir</CODE> and friends in your shell scripts and other files, rather
let @command{make} manage their replacement. For instance Autoconf
ships templates of its shell scripts ending with <SAMP>`.sh'</SAMP>, and uses
this Makefile snippet:
<PRE>
.sh:
rm -f $@ $@.tmp
sed 's,@datadir\@,$(pkgdatadir),g' $< >$@.tmp
chmod +x $@.tmp
mv $@.tmp $@
</PRE>
<P>
Three things are noteworthy:
<DL COMPACT>
<DT><SAMP>`@datadir\@'</SAMP>
<DD>
The backslash prevents @command{configure} from replacing
<SAMP>`@datadir@'</SAMP> in the sed expression itself.
<DT><SAMP>`$(pkgdatadir)'</SAMP>
<DD>
Don't use <SAMP>`@pkgdatadir@'</SAMP>! Use the matching makefile variable
instead.
<DT><SAMP>`,'</SAMP>
<DD>
Don't use <SAMP>`/'</SAMP> in the sed expression(s) since most probably the
variables you use, such as <SAMP>`$(pkgdatadir)'</SAMP>, will contain
some.
</DL>
<H3><A NAME="SEC25" HREF="autoconf_toc.html#TOC25">Build Directories</A></H3>
<P>
You can support compiling a software package for several architectures
simultaneously from the same copy of the source code. The object files
for each architecture are kept in their own directory.
<P>
To support doing this, <CODE>make</CODE> uses the <CODE>VPATH</CODE> variable to
find the files that are in the source directory. GNU <CODE>make</CODE>
and most other recent <CODE>make</CODE> programs can do this. Older
<CODE>make</CODE> programs do not support <CODE>VPATH</CODE>; when using them, the
source code must be in the same directory as the object files.
<P>
To support <CODE>VPATH</CODE>, each <TT>`Makefile.in'</TT> should contain two
lines that look like:
<PRE>
srcdir = @srcdir@
VPATH = @srcdir@
</PRE>
<P>
Do not set <CODE>VPATH</CODE> to the value of another variable, for example
<SAMP>`VPATH = $(srcdir)'</SAMP>, because some versions of <CODE>make</CODE> do not do
variable substitutions on the value of <CODE>VPATH</CODE>.
<P>
@command{configure} substitutes in the correct value for <CODE>srcdir</CODE> when
it produces <TT>`Makefile'</TT>.
<P>
Do not use the <CODE>make</CODE> variable <CODE>$<</CODE>, which expands to the
file name of the file in the source directory (found with <CODE>VPATH</CODE>),
except in implicit rules. (An implicit rule is one such as <SAMP>`.c.o'</SAMP>,
which tells how to create a <TT>`.o'</TT> file from a <TT>`.c'</TT> file.) Some
versions of <CODE>make</CODE> do not set <CODE>$<</CODE> in explicit rules; they
expand it to an empty value.
<P>
Instead, <TT>`Makefile'</TT> command lines should always refer to source
files by prefixing them with <SAMP>`$(srcdir)/'</SAMP>. For example:
<PRE>
time.info: time.texinfo
$(MAKEINFO) $(srcdir)/time.texinfo
</PRE>
<H3><A NAME="SEC26" HREF="autoconf_toc.html#TOC26">Automatic Remaking</A></H3>
<P>
You can put rules like the following in the top-level <TT>`Makefile.in'</TT>
for a package to automatically update the configuration information when
you change the configuration files. This example includes all of the
optional files, such as <TT>`aclocal.m4'</TT> and those related to
configuration header files. Omit from the <TT>`Makefile.in'</TT> rules for
any of these files that your package does not use.
<P>
The <SAMP>`$(srcdir)/'</SAMP> prefix is included because of limitations in the
<CODE>VPATH</CODE> mechanism.
<P>
The <TT>`stamp-'</TT> files are necessary because the timestamps of
<TT>`config.h.in'</TT> and <TT>`config.h'</TT> will not be changed if remaking
them does not change their contents. This feature avoids unnecessary
recompilation. You should include the file <TT>`stamp-h.in'</TT> your
package's distribution, so @command{make} will consider
<TT>`config.h.in'</TT> up to date. Don't use @command{touch}
(see section <A HREF="autoconf.html#SEC119">Limitations of Usual Tools</A>), rather use @command{echo} (using
@command{date} would cause needless differences, hence CVS
conflicts etc.).
<PRE>
$(srcdir)/configure: configure.ac aclocal.m4
cd $(srcdir) && autoconf
# autoheader might not change config.h.in, so touch a stamp file.
$(srcdir)/config.h.in: stamp-h.in
$(srcdir)/stamp-h.in: configure.ac aclocal.m4
cd $(srcdir) && autoheader
echo timestamp > $(srcdir)/stamp-h.in
config.h: stamp-h
stamp-h: config.h.in config.status
./config.status
Makefile: Makefile.in config.status
./config.status
config.status: configure
./config.status --recheck
</PRE>
<P>
(Be careful if you copy these lines directly into your Makefile, as you
will need to convert the indented lines to start with the tab character.)
<P>
In addition, you should use <SAMP>`AC_CONFIG_FILES([stamp-h], [echo
timestamp > stamp-h])'</SAMP> so <TT>`config.status'</TT> will ensure that
<TT>`config.h'</TT> is considered up to date. See section <A HREF="autoconf.html#SEC19">Outputting Files</A>, for more
information about <CODE>AC_OUTPUT</CODE>.
<P>
See section <A HREF="autoconf.html#SEC145">Recreating a Configuration</A>, for more examples of handling
configuration-related dependencies.
<H2><A NAME="SEC27" HREF="autoconf_toc.html#TOC27">Configuration Header Files</A></H2>
<P>
<A NAME="IDX119"></A>
<A NAME="IDX120"></A>
<P>
When a package tests more than a few C preprocessor symbols, the command
lines to pass @option{-D} options to the compiler can get quite long.
This causes two problems. One is that the <CODE>make</CODE> output is hard to
visually scan for errors. More seriously, the command lines can exceed
the length limits of some operating systems. As an alternative to
passing @option{-D} options to the compiler, @command{configure} scripts can
create a C header file containing <SAMP>`#define'</SAMP> directives. The
<CODE>AC_CONFIG_HEADERS</CODE> macro selects this kind of output. It should
be called right after <CODE>AC_INIT</CODE>.
<P>
The package should <SAMP>`#include'</SAMP> the configuration header file before
any other header files, to prevent inconsistencies in declarations (for
example, if it redefines <CODE>const</CODE>). Use <SAMP>`#include <config.h>'</SAMP>
instead of <SAMP>`#include "config.h"'</SAMP>, and pass the C compiler a
@option{-I.} option (or @option{-I..}; whichever directory contains
<TT>`config.h'</TT>). That way, even if the source directory is configured
itself (perhaps to make a distribution), other build directories can
also be configured without finding the <TT>`config.h'</TT> from the source
directory.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_HEADERS</B> <I>(<VAR>header</VAR> ..., @ovar{cmds}, @ovar{init-cmds})</I>
<DD><A NAME="IDX121"></A>
<A NAME="IDX122"></A>
<A NAME="IDX123"></A>
This macro is one of the instantiating macros, see section <A HREF="autoconf.html#SEC20">Taking Configuration Actions</A>. Make <CODE>AC_OUTPUT</CODE> create the file(s) in the
whitespace-separated list <VAR>header</VAR> containing C preprocessor
<CODE>#define</CODE> statements, and replace <SAMP>`@DEFS@'</SAMP> in generated
files with @option{-DHAVE_CONFIG_H} instead of the value of <CODE>DEFS</CODE>.
The usual name for <VAR>header</VAR> is <TT>`config.h'</TT>.
<P>
If <VAR>header</VAR> already exists and its contents are identical to what
<CODE>AC_OUTPUT</CODE> would put in it, it is left alone. Doing this allows
some changes in configuration without needlessly causing object files
that depend on the header file to be recompiled.
<P>
Usually the input file is named <TT>`<VAR>header</VAR>.in'</TT>; however, you can
override the input file name by appending to <VAR>header</VAR>, a
colon-separated list of input files. Examples:
<PRE>
AC_CONFIG_HEADERS([config.h:config.hin])
AC_CONFIG_HEADERS([defines.h:defs.pre:defines.h.in:defs.post])
</PRE>
<P>
Doing this allows you to keep your file names acceptable to MS-DOS, or
to prepend and/or append boilerplate to the file.
</DL>
<P>
See section <A HREF="autoconf.html#SEC20">Taking Configuration Actions</A>, for more details on <VAR>header</VAR>.
<H3><A NAME="SEC28" HREF="autoconf_toc.html#TOC28">Configuration Header Templates</A></H3>
<P>
<A NAME="IDX124"></A>
<A NAME="IDX125"></A>
<P>
Your distribution should contain a template file that looks as you want
the final header file to look, including comments, with <CODE>#undef</CODE>
statements which are used as hooks. For example, suppose your
<TT>`configure.ac'</TT> makes these calls:
<PRE>
AC_CONFIG_HEADERS([conf.h])
AC_CHECK_HEADERS([unistd.h])
</PRE>
<P>
Then you could have code like the following in <TT>`conf.h.in'</TT>. On
systems that have <TT>`unistd.h'</TT>, @command{configure} will <SAMP>`#define'</SAMP>
<SAMP>`HAVE_UNISTD_H'</SAMP> to 1. On other systems, the whole line will be
commented out (in case the system predefines that symbol).
<PRE>
/* Define as 1 if you have unistd.h. */
#undef HAVE_UNISTD_H
</PRE>
<P>
You can then decode the configuration header using the preprocessor
directives:
<PRE>
#include <conf.h>
#if HAVE_UNISTD_H
# include <unistd.h>
#else
/* We are in trouble. */
#endif
</PRE>
<P>
The use of old form templates, with <SAMP>`#define'</SAMP> instead of
<SAMP>`#undef'</SAMP> is strongly discouraged.
<P>
Since it is a tedious task to keep a template header up to date, you may
use @command{autoheader} to generate it, see section <A HREF="autoconf.html#SEC29">Using @command{autoheader} to Create @file{config.h.in}</A>.
<H3><A NAME="SEC29" HREF="autoconf_toc.html#TOC29">Using @command{autoheader} to Create <TT>`config.h.in'</TT></A></H3>
<P>
<A NAME="IDX126"></A>
<P>
The @command{autoheader} program can create a template file of C
<SAMP>`#define'</SAMP> statements for @command{configure} to use. If
<TT>`configure.ac'</TT> invokes <CODE>AC_CONFIG_HEADERS(<VAR>file</VAR>)</CODE>,
@command{autoheader} creates <TT>`<VAR>file</VAR>.in'</TT>; if multiple file
arguments are given, the first one is used. Otherwise,
@command{autoheader} creates <TT>`config.h.in'</TT>.
<P>
In order to do its job, @command{autoheader} needs you to document all
of the symbols that you might use; i.e., there must be at least one
<CODE>AC_DEFINE</CODE> or one <CODE>AC_DEFINE_UNQUOTED</CODE> using its third
argument for each symbol (see section <A HREF="autoconf.html#SEC80">Defining C Preprocessor Symbols</A>). An additional
constraint is that the first argument of <CODE>AC_DEFINE</CODE> must be a
literal. Note that all symbols defined by Autoconf's built-in tests are
already documented properly; you only need to document those that you
define yourself.
<P>
You might wonder why @command{autoheader} is needed: after all, why
would @command{configure} need to "patch" a <TT>`config.h.in'</TT> to
produce a <TT>`config.h'</TT> instead of just creating <TT>`config.h'</TT> from
scratch? Well, when everything rocks, the answer is just that we are
wasting our time maintaining @command{autoheader}: generating
<TT>`config.h'</TT> directly is all that is needed. When things go wrong,
however, you'll be thankful for the existence of @command{autoheader}.
<P>
The fact that the symbols are documented is important in order to
<EM>check</EM> that <TT>`config.h'</TT> makes sense. The fact that there is a
well defined list of symbols that should be <CODE>#define</CODE>'d (or not) is
also important for people who are porting packages to environments where
@command{configure} cannot be run: they just have to @emph{fill in the
blanks}.
<P>
But let's come back to the point: @command{autoheader}'s invocation...
<P>
If you give @command{autoheader} an argument, it uses that file instead
of <TT>`configure.ac'</TT> and writes the header file to the standard output
instead of to <TT>`config.h.in'</TT>. If you give @command{autoheader} an
argument of @option{-}, it reads the standard input instead of
<TT>`configure.ac'</TT> and writes the header file to the standard output.
<P>
@command{autoheader} accepts the following options:
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the command line options and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version number of Autoconf and exit.
<DT>@option{--verbose}
<DD>
<DT>@option{-v}
<DD>
Report processing steps.
<DT>@option{--debug}
<DD>
<DT>@option{-d}
<DD>
Don't remove the temporary files.
<DT>@option{--force}
<DD>
<DT>@option{-f}
<DD>
Remake the template file even if newer than its input files.
<DT>@option{--include=<VAR>dir</VAR>}
<DD>
<DT>@option{-I <VAR>dir</VAR>}
<DD>
Also look for input files in <VAR>dir</VAR>. Multiple invocations accumulate.
Directories are browsed from last to first.
<DT>@option{--warnings=<VAR>category</VAR>}
<DD>
<DT>@option{-W <VAR>category</VAR>}
<DD>
<A NAME="IDX127"></A>
Report the warnings related to <VAR>category</VAR> (which can actually be a
comma separated list). Current categories include:
<DL COMPACT>
<DT><SAMP>`obsolete'</SAMP>
<DD>
report the uses of obsolete constructs
<DT><SAMP>`all'</SAMP>
<DD>
report all the warnings
<DT><SAMP>`none'</SAMP>
<DD>
report none
<DT><SAMP>`error'</SAMP>
<DD>
treats warnings as errors
<DT><SAMP>`no-<VAR>category</VAR>'</SAMP>
<DD>
disable warnings falling into <VAR>category</VAR>
</DL>
</DL>
<H3><A NAME="SEC30" HREF="autoconf_toc.html#TOC30">Autoheader Macros</A></H3>
<P>
@command{autoheader} scans <TT>`configure.ac'</TT> and figures out which C
preprocessor symbols it might define. It knows how to generate
templates for symbols defined by <CODE>AC_CHECK_HEADERS</CODE>,
<CODE>AC_CHECK_FUNCS</CODE> etc., but if you <CODE>AC_DEFINE</CODE> any additional
symbol, you must define a template for it. If there are missing
templates, @command{autoheader} fails with an error message.
<P>
The simplest way to create a template for a <VAR>symbol</VAR> is to supply
the <VAR>description</VAR> argument to an <SAMP>`AC_DEFINE(<VAR>symbol</VAR>)'</SAMP>; see
section <A HREF="autoconf.html#SEC80">Defining C Preprocessor Symbols</A>. You may also use one of the following macros.
<P>
<DL>
<DT><U>Macro:</U> <B>AH_VERBATIM</B> <I>(<VAR>key</VAR>, <VAR>template</VAR>)</I>
<DD><A NAME="IDX128"></A>
<A NAME="IDX129"></A>
<A NAME="IDX130"></A>
Tell @command{autoheader} to include the <VAR>template</VAR> as-is in the header
template file. This <VAR>template</VAR> is associated with the <VAR>key</VAR>,
which is used to sort all the different templates and guarantee their
uniqueness. It should be the symbol that can be <CODE>AC_DEFINE</CODE>'d.
<P>
For example:
<PRE>
AH_VERBATIM([_GNU_SOURCE],
[/* Enable GNU extensions on systems that have them. */
#ifndef _GNU_SOURCE
# define _GNU_SOURCE
#endif])
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AH_TEMPLATE</B> <I>(<VAR>key</VAR>, <VAR>description</VAR>)</I>
<DD><A NAME="IDX131"></A>
<A NAME="IDX132"></A>
<A NAME="IDX133"></A>
Tell @command{autoheader} to generate a template for <VAR>key</VAR>. This macro
generates standard templates just like <CODE>AC_DEFINE</CODE> when a
<VAR>description</VAR> is given.
<P>
For example:
<PRE>
AH_TEMPLATE([CRAY_STACKSEG_END],
[Define to one of _getb67, GETB67, getb67
for Cray-2 and Cray-YMP systems. This
function is required for alloca.c support
on those systems.])
</PRE>
<P>
will generate the following template, with the description properly
justified.
<PRE>
/* Define to one of _getb67, GETB67, getb67 for Cray-2 and
Cray-YMP systems. This function is required for alloca.c
support on those systems. */
#undef CRAY_STACKSEG_END
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AH_TOP</B> <I>(<VAR>text</VAR>)</I>
<DD><A NAME="IDX134"></A>
<A NAME="IDX135"></A>
<A NAME="IDX136"></A>
Include <VAR>text</VAR> at the top of the header template file.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AH_BOTTOM</B> <I>(<VAR>text</VAR>)</I>
<DD><A NAME="IDX137"></A>
<A NAME="IDX138"></A>
<A NAME="IDX139"></A>
Include <VAR>text</VAR> at the bottom of the header template file.
</DL>
<H2><A NAME="SEC31" HREF="autoconf_toc.html#TOC31">Running Arbitrary Configuration Commands</A></H2>
<P>
You execute arbitrary commands either before, during and after
<TT>`config.status'</TT> is run. The three following macros accumulate the
commands to run when they are called multiple times.
<CODE>AC_CONFIG_COMMANDS</CODE> replaces the obsolete macro
<CODE>AC_OUTPUT_COMMANDS</CODE>, see section <A HREF="autoconf.html#SEC150">Obsolete Macros</A>, for details.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_COMMANDS</B> <I>(<VAR>tag</VAR>..., @ovar{cmds}, @ovar{init-cmds})</I>
<DD><A NAME="IDX140"></A>
<A NAME="IDX141"></A>
Specify additional shell commands to run at the end of
<TT>`config.status'</TT>, and shell commands to initialize any variables
from @command{configure}. Associate the commands to the <VAR>tag</VAR>. Since
typically the <VAR>cmds</VAR> create a file, <VAR>tag</VAR> should naturally be
the name of that file. This macro is one of the instantiating macros,
see section <A HREF="autoconf.html#SEC20">Taking Configuration Actions</A>.
<P>
Here is an unrealistic example:
<PRE>
fubar=42
AC_CONFIG_COMMANDS([fubar],
[echo this is extra $fubar, and so on.],
[fubar=$fubar])
</PRE>
<P>
Here is a better one:
<PRE>
AC_CONFIG_COMMANDS([time-stamp], [date >time-stamp])
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_COMMANDS_PRE</B> <I>(<VAR>cmds</VAR>)</I>
<DD><A NAME="IDX142"></A>
<A NAME="IDX143"></A>
Execute the <VAR>cmds</VAR> right before creating <TT>`config.status'</TT>. A
typical use is computing values derived from variables built during the
execution of @command{configure}:
<PRE>
AC_CONFIG_COMMANDS_PRE(
[LTLIBOBJS=`echo $LIBOBJS | sed 's/\.o/\.lo/g'`
AC_SUBST(LTLIBOBJS)])
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_COMMANDS_POST</B> <I>(<VAR>cmds</VAR>)</I>
<DD><A NAME="IDX144"></A>
<A NAME="IDX145"></A>
Execute the <VAR>cmds</VAR> right after creating <TT>`config.status'</TT>.
</DL>
<H2><A NAME="SEC32" HREF="autoconf_toc.html#TOC32">Creating Configuration Links</A></H2>
<P>
You may find it convenient to create links whose destinations depend upon
results of tests. One can use <CODE>AC_CONFIG_COMMANDS</CODE> but the
creation of relative symbolic links can be delicate when the package is
built in another directory than its sources.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_LINKS</B> <I>(<VAR>dest</VAR>:<VAR>source</VAR>..., @ovar{cmds}, @ovar{init-cmds})</I>
<DD><A NAME="IDX146"></A>
<A NAME="IDX147"></A>
<A NAME="IDX148"></A>
Make <CODE>AC_OUTPUT</CODE> link each of the existing files <VAR>source</VAR> to
the corresponding link name <VAR>dest</VAR>. Makes a symbolic link if
possible, otherwise a hard link. The <VAR>dest</VAR> and <VAR>source</VAR> names
should be relative to the top level source or build directory. This
macro is one of the instantiating macros, see section <A HREF="autoconf.html#SEC20">Taking Configuration Actions</A>.
<P>
For example, this call:
<PRE>
AC_CONFIG_LINKS(host.h:config/$machine.h
object.h:config/$obj_format.h)
</PRE>
<P>
creates in the current directory <TT>`host.h'</TT> as a link to
<TT>`<VAR>srcdir</VAR>/config/$machine.h'</TT>, and <TT>`object.h'</TT> as a
link to <TT>`<VAR>srcdir</VAR>/config/$obj_format.h'</TT>.
<P>
The tempting value <SAMP>`.'</SAMP> for <VAR>dest</VAR> is invalid: it makes it
impossible for <SAMP>`config.status'</SAMP> to guess the links to establish.
<P>
One can then run:
<PRE>
./config.status host.h object.h
</PRE>
<P>
to create the links.
</DL>
<H2><A NAME="SEC33" HREF="autoconf_toc.html#TOC33">Configuring Other Packages in Subdirectories</A></H2>
<P>
In most situations, calling <CODE>AC_OUTPUT</CODE> is sufficient to produce
<TT>`Makefile'</TT>s in subdirectories. However, @command{configure} scripts
that control more than one independent package can use
<CODE>AC_CONFIG_SUBDIRS</CODE> to run @command{configure} scripts for other
packages in subdirectories.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONFIG_SUBDIRS</B> <I>(<VAR>dir</VAR> ...)</I>
<DD><A NAME="IDX149"></A>
<A NAME="IDX150"></A>
<A NAME="IDX151"></A>
Make <CODE>AC_OUTPUT</CODE> run @command{configure} in each subdirectory
<VAR>dir</VAR> in the given whitespace-separated list. Each <VAR>dir</VAR> should
be a literal, i.e., please do not use:
<PRE>
if test "$package_foo_enabled" = yes; then
$my_subdirs="$my_subdirs foo"
fi
AC_CONFIG_SUBDIRS($my_subdirs)
</PRE>
<P>
because this prevents <SAMP>`./configure --help=recursive'</SAMP> from
displaying the options of the package <CODE>foo</CODE>. Rather, you should
write:
<PRE>
if test "$package_foo_enabled" = yes; then
AC_CONFIG_SUBDIRS(foo)
fi
</PRE>
<P>
If a given <VAR>dir</VAR> is not found, an error is reported: if the
subdirectory is optional, write:
<PRE>
if test -d $srcdir/foo; then
AC_CONFIG_SUBDIRS(foo)
fi
</PRE>
<P>
If a given <VAR>dir</VAR> contains @command{configure.gnu}, it is run instead
of @command{configure}. This is for packages that might use a
non-autoconf script @command{Configure}, which can't be called through a
wrapper @command{configure} since it would be the same file on
case-insensitive filesystems. Likewise, if a <VAR>dir</VAR> contains
<TT>`configure.ac'</TT> but no @command{configure}, the Cygnus
@command{configure} script found by <CODE>AC_CONFIG_AUX_DIR</CODE> is used.
<P>
The subdirectory @command{configure} scripts are given the same command
line options that were given to this @command{configure} script, with minor
changes if needed, which include:
<UL>
<LI>
adjusting a relative path for the cache file;
<LI>
adjusting a relative path for the source directory;
<LI>
propagating the current value of <CODE>$prefix</CODE>, including if it was
defaulted, and if default values of the top level and of sub directory
<TT>`configure'</TT> differ.
</UL>
<P>
This macro also sets the output variable <CODE>subdirs</CODE> to the list of
directories <SAMP>`<VAR>dir</VAR> ...'</SAMP>. <TT>`Makefile'</TT> rules can use
this variable to determine which subdirectories to recurse into. This
macro may be called multiple times.
</DL>
<H2><A NAME="SEC34" HREF="autoconf_toc.html#TOC34">Default Prefix</A></H2>
<P>
By default, @command{configure} sets the prefix for files it installs to
<TT>`/usr/local'</TT>. The user of @command{configure} can select a different
prefix using the @option{--prefix} and @option{--exec-prefix} options.
There are two ways to change the default: when creating
@command{configure}, and when running it.
<P>
Some software packages might want to install in a directory besides
<TT>`/usr/local'</TT> by default. To accomplish that, use the
<CODE>AC_PREFIX_DEFAULT</CODE> macro.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PREFIX_DEFAULT</B> <I>(<VAR>prefix</VAR>)</I>
<DD><A NAME="IDX152"></A>
<A NAME="IDX153"></A>
Set the default installation prefix to <VAR>prefix</VAR> instead of
<TT>`/usr/local'</TT>.
</DL>
<P>
It may be convenient for users to have @command{configure} guess the
installation prefix from the location of a related program that they
have already installed. If you wish to do that, you can call
<CODE>AC_PREFIX_PROGRAM</CODE>.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PREFIX_PROGRAM</B> <I>(<VAR>program</VAR>)</I>
<DD><A NAME="IDX154"></A>
<A NAME="IDX155"></A>
If the user did not specify an installation prefix (using the
@option{--prefix} option), guess a value for it by looking for
<VAR>program</VAR> in <CODE>PATH</CODE>, the way the shell does. If <VAR>program</VAR>
is found, set the prefix to the parent of the directory containing
<VAR>program</VAR>; otherwise leave the prefix specified in
<TT>`Makefile.in'</TT> unchanged. For example, if <VAR>program</VAR> is
<CODE>gcc</CODE> and the <CODE>PATH</CODE> contains <TT>`/usr/local/gnu/bin/gcc'</TT>,
set the prefix to <TT>`/usr/local/gnu'</TT>.
</DL>
<H1><A NAME="SEC35" HREF="autoconf_toc.html#TOC35">Existing Tests</A></H1>
<P>
These macros test for particular system features that packages might
need or want to use. If you need to test for a kind of feature that
none of these macros check for, you can probably do it by calling
primitive test macros with appropriate arguments (see section <A HREF="autoconf.html#SEC68">Writing Tests</A>).
<P>
These tests print messages telling the user which feature they're
checking for, and what they find. They cache their results for future
@command{configure} runs (see section <A HREF="autoconf.html#SEC82">Caching Results</A>).
<P>
Some of these macros set output variables. See section <A HREF="autoconf.html#SEC22">Substitutions in Makefiles</A>, for how to get their values. The phrase "define
<VAR>name</VAR>" is used below as a shorthand to mean "define C
preprocessor symbol <VAR>name</VAR> to the value 1". See section <A HREF="autoconf.html#SEC80">Defining C Preprocessor Symbols</A>, for how to get those symbol definitions into your program.
<H2><A NAME="SEC36" HREF="autoconf_toc.html#TOC36">Common Behavior</A></H2>
<P>
Much effort has been expended to make Autoconf easy to learn. The most
obvious way to reach this goal is simply to enforce standard interfaces
and behaviors, avoiding exceptions as much as possible. Because of
history and inertia, unfortunately, there are still too many exceptions
in Autoconf; nevertheless, this section describes some of the common
rules.
<H3><A NAME="SEC37" HREF="autoconf_toc.html#TOC37">Standard Symbols</A></H3>
<P>
All the generic macros that <CODE>AC_DEFINE</CODE> a symbol as a result of
their test transform their <VAR>argument</VAR>s to a standard alphabet.
First, <VAR>argument</VAR> is converted to upper case and any asterisks
(<SAMP>`*'</SAMP>) are each converted to <SAMP>`P'</SAMP>. Any remaining characters
that are not alphanumeric are converted to underscores.
<P>
For instance,
<PRE>
AC_CHECK_TYPES(struct $Expensive*)
</PRE>
<P>
will define the symbol <SAMP>`HAVE_STRUCT__EXPENSIVEP'</SAMP> if the check
succeeds.
<H3><A NAME="SEC38" HREF="autoconf_toc.html#TOC38">Default Includes</A></H3>
<P>
<A NAME="IDX156"></A>
<P>
Several tests depend upon a set of header files. Since these headers
are not universally available, tests actually have to provide a set of
protected includes, such as:
<PRE>
#if TIME_WITH_SYS_TIME
# include <sys/time.h>
# include <time.h>
#else
# if HAVE_SYS_TIME_H
# include <sys/time.h>
# else
# include <time.h>
# endif
#endif
</PRE>
<P>
Unless you know exactly what you are doing, you should avoid using
unconditional includes, and check the existence of the headers you
include beforehand (see section <A HREF="autoconf.html#SEC48">Header Files</A>).
<P>
Most generic macros provide the following default set of includes:
<PRE>
#include <stdio.h>
#if HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif
#if HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#if STDC_HEADERS
# include <stdlib.h>
# include <stddef.h>
#else
# if HAVE_STDLIB_H
# include <stdlib.h>
# endif
#endif
#if HAVE_STRING_H
# if !STDC_HEADERS && HAVE_MEMORY_H
# include <memory.h>
# endif
# include <string.h>
#endif
#if HAVE_STRINGS_H
# include <strings.h>
#endif
#if HAVE_INTTYPES_H
# include <inttypes.h>
#else
# if HAVE_STDINT_H
# include <stdint.h>
# endif
#endif
#if HAVE_UNISTD_H
# include <unistd.h>
#endif
</PRE>
<P>
If the default includes are used, then Autoconf will automatically check
for the presence of these headers and their compatibility, i.e., you
don't need to run <CODE>AC_HEADERS_STDC</CODE>, nor check for <TT>`stdlib.h'</TT>
etc.
<P>
These headers are checked for in the same order as they are included.
For instance, on some systems <TT>`string.h'</TT> and <TT>`strings.h'</TT> both
exist, but conflict. Then <CODE>HAVE_STRING_H</CODE> will be defined, but
<CODE>HAVE_STRINGS_H</CODE> won't.
<H2><A NAME="SEC39" HREF="autoconf_toc.html#TOC39">Alternative Programs</A></H2>
<P>
<A NAME="IDX157"></A>
<P>
These macros check for the presence or behavior of particular programs.
They are used to choose between several alternative programs and to
decide what to do once one has been chosen. If there is no macro
specifically defined to check for a program you need, and you don't need
to check for any special properties of it, then you can use one of the
general program-check macros.
<H3><A NAME="SEC40" HREF="autoconf_toc.html#TOC40">Particular Program Checks</A></H3>
<P>
These macros check for particular programs--whether they exist, and
in some cases whether they support certain features.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_AWK</B>
<DD><A NAME="IDX158"></A>
<A NAME="IDX159"></A>
<A NAME="IDX160"></A>
Check for <CODE>gawk</CODE>, <CODE>mawk</CODE>, <CODE>nawk</CODE>, and <CODE>awk</CODE>, in that
order, and set output variable <CODE>AWK</CODE> to the first one that is found.
It tries <CODE>gawk</CODE> first because that is reported to be the
best implementation.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_INSTALL</B>
<DD><A NAME="IDX161"></A>
<A NAME="IDX162"></A>
<A NAME="IDX163"></A>
<A NAME="IDX164"></A>
<A NAME="IDX165"></A>
<A NAME="IDX166"></A>
Set output variable <CODE>INSTALL</CODE> to the path of a BSD compatible
<CODE>install</CODE> program, if one is found in the current <CODE>PATH</CODE>.
Otherwise, set <CODE>INSTALL</CODE> to <SAMP>`<VAR>dir</VAR>/install-sh -c'</SAMP>,
checking the directories specified to <CODE>AC_CONFIG_AUX_DIR</CODE> (or its
default directories) to determine <VAR>dir</VAR> (see section <A HREF="autoconf.html#SEC19">Outputting Files</A>). Also set
the variables <CODE>INSTALL_PROGRAM</CODE> and <CODE>INSTALL_SCRIPT</CODE> to
<SAMP>`${INSTALL}'</SAMP> and <CODE>INSTALL_DATA</CODE> to <SAMP>`${INSTALL} -m 644'</SAMP>.
<P>
This macro screens out various instances of <CODE>install</CODE> known not to
work. It prefers to find a C program rather than a shell script, for
speed. Instead of <TT>`install-sh'</TT>, it can also use <TT>`install.sh'</TT>,
but that name is obsolete because some <CODE>make</CODE> programs have a rule
that creates <TT>`install'</TT> from it if there is no <TT>`Makefile'</TT>.
<P>
Autoconf comes with a copy of <TT>`install-sh'</TT> that you can use. If
you use <CODE>AC_PROG_INSTALL</CODE>, you must include either
<TT>`install-sh'</TT> or <TT>`install.sh'</TT> in your distribution, or
@command{configure} will produce an error message saying it can't find
them--even if the system you're on has a good <CODE>install</CODE> program.
This check is a safety measure to prevent you from accidentally leaving
that file out, which would prevent your package from installing on
systems that don't have a BSD-compatible <CODE>install</CODE> program.
<P>
If you need to use your own installation program because it has features
not found in standard <CODE>install</CODE> programs, there is no reason to use
<CODE>AC_PROG_INSTALL</CODE>; just put the file name of your program into your
<TT>`Makefile.in'</TT> files.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_LEX</B>
<DD><A NAME="IDX167"></A>
<A NAME="IDX168"></A>
<A NAME="IDX169"></A>
<A NAME="IDX170"></A>
<A NAME="IDX171"></A>
<A NAME="IDX172"></A>
If <CODE>flex</CODE> is found, set output variable <CODE>LEX</CODE> to <SAMP>`flex'</SAMP>
and <CODE>LEXLIB</CODE> to @option{-lfl}, if that library is in a standard
place. Otherwise set <CODE>LEX</CODE> to <SAMP>`lex'</SAMP> and <CODE>LEXLIB</CODE> to
@option{-ll}.
<P>
Define <CODE>YYTEXT_POINTER</CODE> if <CODE>yytext</CODE> is a <SAMP>`char *'</SAMP> instead
of a <SAMP>`char []'</SAMP>. Also set output variable <CODE>LEX_OUTPUT_ROOT</CODE> to
the base of the file name that the lexer generates; usually
<TT>`lex.yy'</TT>, but sometimes something else. These results vary
according to whether <CODE>lex</CODE> or <CODE>flex</CODE> is being used.
<P>
You are encouraged to use Flex in your sources, since it is both more
pleasant to use than plain Lex and the C source it produces is portable.
In order to ensure portability, however, you must either provide a
function <CODE>yywrap</CODE> or, if you don't use it (e.g., your scanner has
no <SAMP>`#include'</SAMP>-like feature), simply include a <SAMP>`%noyywrap'</SAMP>
statement in the scanner's source. Once this done, the scanner is
portable (unless <EM>you</EM> felt free to use nonportable constructs) and
does not depend on any library. In this case, and in this case only, it
is suggested that you use this Autoconf snippet:
<PRE>
AC_PROG_LEX
if test "$LEX" != flex; then
LEX="$SHELL $missing_dir/missing flex"
AC_SUBST(LEX_OUTPUT_ROOT, lex.yy)
AC_SUBST(LEXLIB, '')
fi
</PRE>
<P>
The shell script @command{missing} can be found in the Automake
distribution.
<P>
To ensure backward compatibility, Automake's <CODE>AM_PROG_LEX</CODE> invokes
(indirectly) this macro twice, which will cause an annoying but benign
"<CODE>AC_PROG_LEX</CODE> invoked multiple times" warning. Future versions
of Automake will fix this issue, meanwhile, just ignore this message.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_LN_S</B>
<DD><A NAME="IDX173"></A>
<A NAME="IDX174"></A>
<A NAME="IDX175"></A>
If <SAMP>`ln -s'</SAMP> works on the current file system (the operating system
and file system support symbolic links), set the output variable
<CODE>LN_S</CODE> to <SAMP>`ln -s'</SAMP>; otherwise, if <SAMP>`ln'</SAMP> works, set
<CODE>LN_S</CODE> to <SAMP>`ln'</SAMP> and otherwise set it to <SAMP>`cp -p'</SAMP>.
<P>
If you make a link a directory other than the current directory, its
meaning depends on whether <SAMP>`ln'</SAMP> or <SAMP>`ln -s'</SAMP> is used. To safely
create links using <SAMP>`$(LN_S)'</SAMP>, either find out which form is used
and adjust the arguments, or always invoke <CODE>ln</CODE> in the directory
where the link is to be created.
<P>
In other words, it does not work to do:
<PRE>
$(LN_S) foo /x/bar
</PRE>
<P>
Instead, do:
<PRE>
(cd /x && $(LN_S) foo bar)
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_RANLIB</B>
<DD><A NAME="IDX176"></A>
<A NAME="IDX177"></A>
<A NAME="IDX178"></A>
Set output variable <CODE>RANLIB</CODE> to <SAMP>`ranlib'</SAMP> if <CODE>ranlib</CODE>
is found, and otherwise to <SAMP>`:'</SAMP> (do nothing).
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_YACC</B>
<DD><A NAME="IDX179"></A>
<A NAME="IDX180"></A>
<A NAME="IDX181"></A>
If <CODE>bison</CODE> is found, set output variable <CODE>YACC</CODE> to <SAMP>`bison
-y'</SAMP>. Otherwise, if <CODE>byacc</CODE> is found, set <CODE>YACC</CODE> to
<SAMP>`byacc'</SAMP>. Otherwise set <CODE>YACC</CODE> to <SAMP>`yacc'</SAMP>.
</DL>
<H3><A NAME="SEC41" HREF="autoconf_toc.html#TOC41">Generic Program and File Checks</A></H3>
<P>
These macros are used to find programs not covered by the "particular"
test macros. If you need to check the behavior of a program as well as
find out whether it is present, you have to write your own test for it
(see section <A HREF="autoconf.html#SEC68">Writing Tests</A>). By default, these macros use the environment
variable <CODE>PATH</CODE>. If you need to check for a program that might not
be in the user's <CODE>PATH</CODE>, you can pass a modified path to use
instead, like this:
<PRE>
AC_PATH_PROG([INETD], [inetd], [/usr/libexec/inetd],
[$PATH:/usr/libexec:/usr/sbin:/usr/etc:etc])
</PRE>
<P>
You are strongly encouraged to declare the <VAR>variable</VAR> passed to
<CODE>AC_CHECK_PROG</CODE> etc. as precious, See section <A HREF="autoconf.html#SEC81">Setting Output Variables</A>,
<CODE>AC_ARG_VAR</CODE>, for more details.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_PROG</B> <I>(<VAR>variable</VAR>, <VAR>prog-to-check-for</VAR>, <VAR>value-if-found</VAR>, @ovar{value-if-not-found}, @ovar{path}, @ovar{reject})</I>
<DD><A NAME="IDX182"></A>
<A NAME="IDX183"></A>
Check whether program <VAR>prog-to-check-for</VAR> exists in <CODE>PATH</CODE>. If
it is found, set <VAR>variable</VAR> to <VAR>value-if-found</VAR>, otherwise to
<VAR>value-if-not-found</VAR>, if given. Always pass over <VAR>reject</VAR> (an
absolute file name) even if it is the first found in the search path; in
that case, set <VAR>variable</VAR> using the absolute file name of the
<VAR>prog-to-check-for</VAR> found that is not <VAR>reject</VAR>. If
<VAR>variable</VAR> was already set, do nothing. Calls <CODE>AC_SUBST</CODE> for
<VAR>variable</VAR>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_PROGS</B> <I>(<VAR>variable</VAR>, <VAR>progs-to-check-for</VAR>, @ovar{value-if-not-found}, @ovar{path})</I>
<DD><A NAME="IDX184"></A>
<A NAME="IDX185"></A>
Check for each program in the whitespace-separated list
<VAR>progs-to-check-for</VAR> exists on the <CODE>PATH</CODE>. If it is found, set
<VAR>variable</VAR> to the name of that program. Otherwise, continue
checking the next program in the list. If none of the programs in the
list are found, set <VAR>variable</VAR> to <VAR>value-if-not-found</VAR>; if
<VAR>value-if-not-found</VAR> is not specified, the value of <VAR>variable</VAR>
is not changed. Calls <CODE>AC_SUBST</CODE> for <VAR>variable</VAR>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_TOOL</B> <I>(<VAR>variable</VAR>, <VAR>prog-to-check-for</VAR>, @ovar{value-if-not-found}, @ovar{path})</I>
<DD><A NAME="IDX186"></A>
<A NAME="IDX187"></A>
Like <CODE>AC_CHECK_PROG</CODE>, but first looks for <VAR>prog-to-check-for</VAR>
with a prefix of the host type as determined by
<CODE>AC_CANONICAL_HOST</CODE>, followed by a dash (see section <A HREF="autoconf.html#SEC123">Getting the Canonical System Type</A>).
For example, if the user runs <SAMP>`configure --host=i386-gnu'</SAMP>, then
this call:
<PRE>
AC_CHECK_TOOL(RANLIB, ranlib, :)
</PRE>
<P>
sets <CODE>RANLIB</CODE> to <TT>`i386-gnu-ranlib'</TT> if that program exists in
<CODE>PATH</CODE>, or otherwise to <SAMP>`ranlib'</SAMP> if that program exists in
<CODE>PATH</CODE>, or to <SAMP>`:'</SAMP> if neither program exists.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_TOOLS</B> <I>(<VAR>variable</VAR>, <VAR>progs-to-check-for</VAR>, @ovar{value-if-not-found}, @ovar{path})</I>
<DD><A NAME="IDX188"></A>
<A NAME="IDX189"></A>
Like <CODE>AC_CHECK_TOOL</CODE>, each of the tools in the list
<VAR>progs-to-check-for</VAR> are checked with a prefix of the host type as
determined by <CODE>AC_CANONICAL_HOST</CODE>, followed by a dash
(see section <A HREF="autoconf.html#SEC123">Getting the Canonical System Type</A>). If none of the tools can be found with a
prefix, then the first one without a prefix is used. If a tool is found,
set <VAR>variable</VAR> to the name of that program. If none of the tools in
the list are found, set <VAR>variable</VAR> to <VAR>value-if-not-found</VAR>; if
<VAR>value-if-not-found</VAR> is not specified, the value of <VAR>variable</VAR>
is not changed. Calls <CODE>AC_SUBST</CODE> for <VAR>variable</VAR>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PATH_PROG</B> <I>(<VAR>variable</VAR>, <VAR>prog-to-check-for</VAR>, @ovar{value-if-not-found}, @ovar{path})</I>
<DD><A NAME="IDX190"></A>
<A NAME="IDX191"></A>
Like <CODE>AC_CHECK_PROG</CODE>, but set <VAR>variable</VAR> to the entire
path of <VAR>prog-to-check-for</VAR> if found.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PATH_PROGS</B> <I>(<VAR>variable</VAR>, <VAR>progs-to-check-for</VAR>, @ovar{value-if-not-found}, @ovar{path})</I>
<DD><A NAME="IDX192"></A>
<A NAME="IDX193"></A>
Like <CODE>AC_CHECK_PROGS</CODE>, but if any of <VAR>progs-to-check-for</VAR>
are found, set <VAR>variable</VAR> to the entire path of the program
found.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PATH_TOOL</B> <I>(<VAR>variable</VAR>, <VAR>prog-to-check-for</VAR>, @ovar{value-if-not-found}, @ovar{path})</I>
<DD><A NAME="IDX194"></A>
<A NAME="IDX195"></A>
Like <CODE>AC_CHECK_TOOL</CODE>, but set <VAR>variable</VAR> to the entire
path of the program if it is found.
</DL>
<H2><A NAME="SEC42" HREF="autoconf_toc.html#TOC42">Files</A></H2>
<P>
<A NAME="IDX196"></A>
<P>
You might also need to check for the existence of files. Before using
these macros, ask yourself whether a run time test might not be a better
solution. Be aware that, like most Autoconf macros, they test a feature
of the host machine, and therefore, they die when cross-compiling.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_FILE</B> <I>(<VAR>file</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX197"></A>
<A NAME="IDX198"></A>
Check whether file <VAR>file</VAR> exists on the native system. If it is
found, execute <VAR>action-if-found</VAR>, otherwise do
<VAR>action-if-not-found</VAR>, if given.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_FILES</B> <I>(<VAR>files</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX199"></A>
<A NAME="IDX200"></A>
Executes <CODE>AC_CHECK_FILE</CODE> once for each file listed in <VAR>files</VAR>.
Additionally, defines <SAMP>`HAVE_<VAR>file</VAR>'</SAMP> (see section <A HREF="autoconf.html#SEC37">Standard Symbols</A>)
for each file found.
</DL>
<H2><A NAME="SEC43" HREF="autoconf_toc.html#TOC43">Library Files</A></H2>
<P>
<A NAME="IDX201"></A>
<P>
The following macros check for the presence of certain C, C++ or Fortran
77 library archive files.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_LIB</B> <I>(<VAR>library</VAR>, <VAR>function</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @ovar{other-libraries})</I>
<DD><A NAME="IDX202"></A>
<A NAME="IDX203"></A>
Depending on the current language(see section <A HREF="autoconf.html#SEC78">Language Choice</A>), try to
ensure that the C, C++, or Fortran 77 function <VAR>function</VAR> is
available by checking whether a test program can be linked with the
library <VAR>library</VAR> to get the function. <VAR>library</VAR> is the base
name of the library; e.g., to check for @option{-lmp}, use <SAMP>`mp'</SAMP> as
the <VAR>library</VAR> argument.
<P>
<VAR>action-if-found</VAR> is a list of shell commands to run if the link
with the library succeeds; <VAR>action-if-not-found</VAR> is a list of shell
commands to run if the link fails. If <VAR>action-if-found</VAR> is not
specified, the default action will prepend @option{-l<VAR>library</VAR>} to
<CODE>LIBS</CODE> and define <SAMP>`HAVE_LIB<VAR>library</VAR>'</SAMP> (in all
capitals). This macro is intended to support building of <CODE>LIBS</CODE> in
a right-to-left (least-dependent to most-dependent) fashion such that
library dependencies are satisfied as a natural side-effect of
consecutive tests. Some linkers are very sensitive to library ordering
so the order in which <CODE>LIBS</CODE> is generated is important to reliable
detection of libraries.
<P>
If linking with <VAR>library</VAR> results in unresolved symbols that would
be resolved by linking with additional libraries, give those libraries
as the <VAR>other-libraries</VAR> argument, separated by spaces:
e.g. @option{-lXt -lX11}. Otherwise, this macro will fail to detect
that <VAR>library</VAR> is present, because linking the test program will
always fail with unresolved symbols. The <VAR>other-libraries</VAR> argument
should be limited to cases where it is desirable to test for one library
in the presence of another that is not already in <CODE>LIBS</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_SEARCH_LIBS</B> <I>(<VAR>function</VAR>, <VAR>search-libs</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @ovar{other-libraries})</I>
<DD><A NAME="IDX204"></A>
<A NAME="IDX205"></A>
Search for a library defining <VAR>function</VAR> if it's not already
available. This equates to calling <CODE>AC_TRY_LINK_FUNC</CODE> first
with no libraries, then for each library listed in <VAR>search-libs</VAR>.
<P>
Add @option{-l<VAR>library</VAR>} to <CODE>LIBS</CODE> for the first library found
to contain <VAR>function</VAR>, and run <VAR>action-if-found</VAR>. If the
function is not found, run <VAR>action-if-not-found</VAR>.
<P>
If linking with <VAR>library</VAR> results in unresolved symbols that would
be resolved by linking with additional libraries, give those libraries
as the <VAR>other-libraries</VAR> argument, separated by spaces:
e.g. @option{-lXt -lX11}. Otherwise, this macro will fail to detect
that <VAR>function</VAR> is present, because linking the test program will
always fail with unresolved symbols.
</DL>
<H2><A NAME="SEC44" HREF="autoconf_toc.html#TOC44">Library Functions</A></H2>
<P>
The following macros check for particular C library functions.
If there is no macro specifically defined to check for a function you need,
and you don't need to check for any special properties of
it, then you can use one of the general function-check macros.
<H3><A NAME="SEC45" HREF="autoconf_toc.html#TOC45">Portability of C Functions</A></H3>
<P>
Most usual functions can either be missing, or be buggy, or be limited
on some architectures. This section tries to make an inventory of these
portability issues. By definition, this list will always require
additions. Please help us keeping it as complete as possible.
<DL COMPACT>
<DT><CODE>snprintf</CODE>
<DD>
<A NAME="IDX206"></A>
<A NAME="IDX207"></A>
The ISO C99 standard says that if the output array isn't big enough and
if no other errors occur, <CODE>snprintf</CODE> and <CODE>vsnprintf</CODE> truncate
the output and return the number of bytes that ought to have been
produced. Some older systems return the truncated length (e.g., GNU C
Library 2.0.x or IRIX 6.5), some a negative value (e.g., earlier GNU C
Library versions), and some the buffer length without truncation (e.g.,
32-bit Solaris 7). Also, some buggy older systems ignore the length and
overrun the buffer (e.g., 64-bit Solaris 7).
<DT><CODE>sprintf</CODE>
<DD>
<A NAME="IDX208"></A>
<A NAME="IDX209"></A>
The ISO C standard says <CODE>sprintf</CODE> and <CODE>vsprintf</CODE> return the
number of bytes written, but on some old systems (SunOS 4 for
instance) they return the buffer pointer instead.
<DT><CODE>sscanf</CODE>
<DD>
<A NAME="IDX210"></A>
On various old systems, e.g. HP-UX 9, <CODE>sscanf</CODE> requires that its
input string is writable (though it doesn't actually change it). This
can be a problem when using @command{gcc} since it normally puts
constant strings in read-only memory
(see section `Incompatibilities' in <CITE>Using and Porting the GNU Compiler Collection</CITE>). Apparently in some cases even
having format strings read-only can be a problem.
<DT><CODE>strnlen</CODE>
<DD>
<A NAME="IDX211"></A>
AIX 4.3 provides a broken version which produces funny results:
<PRE>
strnlen ("foobar", 0) = 0
strnlen ("foobar", 1) = 3
strnlen ("foobar", 2) = 2
strnlen ("foobar", 3) = 1
strnlen ("foobar", 4) = 0
strnlen ("foobar", 5) = 6
strnlen ("foobar", 6) = 6
strnlen ("foobar", 7) = 6
strnlen ("foobar", 8) = 6
strnlen ("foobar", 9) = 6
</PRE>
<DT><CODE>unlink</CODE>
<DD>
<A NAME="IDX212"></A>
The POSIX spec says that <CODE>unlink</CODE> causes the given files to be
removed only after there are no more open file handles for it. Not all
OS's support this behaviour though. So even on systems that provide
<CODE>unlink</CODE>, you cannot portably assume it is OK to call it on files
that are open. For example, on Windows 9x and ME, such a call would fail;
on DOS it could even lead to file system corruption, as the file might end
up being written to after the OS has removed it.
<DT><CODE>va_copy</CODE>
<DD>
<A NAME="IDX213"></A>
The ISO C99 standard provides <CODE>va_copy</CODE> for copying
<CODE>va_list</CODE> variables. It may be available in older environments
too, though possibly as <CODE>__va_copy</CODE> (eg. @command{gcc} in strict
C89 mode). These can be tested with <CODE>#ifdef</CODE>. A fallback to
<CODE>memcpy (&dst, &src, sizeof(va_list))</CODE> will give maximum
portability.
<DT><CODE>va_list</CODE>
<DD>
<A NAME="IDX214"></A>
<CODE>va_list</CODE> is not necessarily just a pointer. It can be a
<CODE>struct</CODE> (eg. @command{gcc} on Alpha), which means <CODE>NULL</CODE> is
not portable. Or it can be an array (eg. @command{gcc} in some
PowerPC configurations), which means as a function parameter it can be
effectively call-by-reference and library routines might modify the
value back in the caller (eg. <CODE>vsnprintf</CODE> in the GNU C Library
2.1).
<DT>Signed <CODE>>></CODE>
<DD>
Normally the C <CODE>>></CODE> right shift of a signed type replicates the
high bit, giving a so-called "arithmetic" shift. But care should be
taken since the ISO C standard doesn't require that behaviour. On those
few processors without a native arithmetic shift (for instance Cray
vector systems) zero bits may be shifted in, the same as a shift of an
unsigned type.
</DL>
<H3><A NAME="SEC46" HREF="autoconf_toc.html#TOC46">Particular Function Checks</A></H3>
<P>
<A NAME="IDX215"></A>
<P>
These macros check for particular C functions--whether they exist, and
in some cases how they respond when given certain arguments.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_ALLOCA</B>
<DD><A NAME="IDX216"></A>
<A NAME="IDX217"></A>
<A NAME="IDX218"></A>
<A NAME="IDX219"></A>
<A NAME="IDX220"></A>
<A NAME="IDX221"></A>
Check how to get <CODE>alloca</CODE>. Tries to get a builtin version by
checking for <TT>`alloca.h'</TT> or the predefined C preprocessor macros
<CODE>__GNUC__</CODE> and <CODE>_AIX</CODE>. If this macro finds <TT>`alloca.h'</TT>,
it defines <CODE>HAVE_ALLOCA_H</CODE>.
<P>
If those attempts fail, it looks for the function in the standard C
library. If any of those methods succeed, it defines
<CODE>HAVE_ALLOCA</CODE>. Otherwise, it sets the output variable
<CODE>ALLOCA</CODE> to <SAMP>`alloca.o'</SAMP> and defines <CODE>C_ALLOCA</CODE> (so
programs can periodically call <SAMP>`alloca(0)'</SAMP> to garbage collect).
This variable is separate from <CODE>LIBOBJS</CODE> so multiple programs can
share the value of <CODE>ALLOCA</CODE> without needing to create an actual
library, in case only some of them use the code in <CODE>LIBOBJS</CODE>.
<P>
This macro does not try to get <CODE>alloca</CODE> from the System V R3
<TT>`libPW'</TT> or the System V R4 <TT>`libucb'</TT> because those libraries
contain some incompatible functions that cause trouble. Some versions
do not even contain <CODE>alloca</CODE> or contain a buggy version. If you
still want to use their <CODE>alloca</CODE>, use <CODE>ar</CODE> to extract
<TT>`alloca.o'</TT> from them instead of compiling <TT>`alloca.c'</TT>.
<P>
Source files that use <CODE>alloca</CODE> should start with a piece of code
like the following, to declare it properly. In some versions of AIX,
the declaration of <CODE>alloca</CODE> must precede everything else except for
comments and preprocessor directives. The <CODE>#pragma</CODE> directive is
indented so that pre-ANSI C compilers will ignore it, rather than
choke on it.
<PRE>
/* AIX requires this to be the first thing in the file. */
#ifndef __GNUC__
# if HAVE_ALLOCA_H
# include <alloca.h>
# else
# ifdef _AIX
#pragma alloca
# else
# ifndef alloca /* predefined by HP cc +Olibcalls */
char *alloca ();
# endif
# endif
# endif
#endif
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_CHOWN</B>
<DD><A NAME="IDX222"></A>
<A NAME="IDX223"></A>
<A NAME="IDX224"></A>
If the <CODE>chown</CODE> function is available and works (in particular, it
should accept @option{-1} for <CODE>uid</CODE> and <CODE>gid</CODE>), define
<CODE>HAVE_CHOWN</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_CLOSEDIR_VOID</B>
<DD><A NAME="IDX225"></A>
<A NAME="IDX226"></A>
<A NAME="IDX227"></A>
<A NAME="IDX228"></A>
If the <CODE>closedir</CODE> function does not return a meaningful value,
define <CODE>CLOSEDIR_VOID</CODE>. Otherwise, callers ought to check its
return value for an error indicator.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_ERROR_AT_LINE</B>
<DD><A NAME="IDX229"></A>
<A NAME="IDX230"></A>
<A NAME="IDX231"></A>
If the <CODE>error_at_line</CODE> function is not found, require an
<CODE>AC_LIBOBJ</CODE> replacement of <SAMP>`error'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_FNMATCH</B>
<DD><A NAME="IDX232"></A>
<A NAME="IDX233"></A>
<A NAME="IDX234"></A>
If the <CODE>fnmatch</CODE> function is available and works (unlike the one on
Solaris 2.4), define <CODE>HAVE_FNMATCH</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_FORK</B>
<DD><A NAME="IDX235"></A>
<A NAME="IDX236"></A>
<A NAME="IDX237"></A>
<A NAME="IDX238"></A>
<A NAME="IDX239"></A>
<A NAME="IDX240"></A>
<A NAME="IDX241"></A>
<A NAME="IDX242"></A>
This macro checks for the <CODE>fork</CODE> and <CODE>vfork</CODE> functions. If a
working <CODE>fork</CODE> is found, define <CODE>HAVE_WORKING_FORK</CODE>. This macro
checks whether <CODE>fork</CODE> is just a stub by trying to run it.
<P>
If <TT>`vfork.h'</TT> is found, define <CODE>HAVE_VFORK_H</CODE>. If a working
<CODE>vfork</CODE> is found, define <CODE>HAVE_WORKING_VFORK</CODE>. Otherwise,
define <CODE>vfork</CODE> to be <CODE>fork</CODE> for backward compatibility with
previous versions of @command{autoconf}. This macro checks for several known
errors in implementations of <CODE>vfork</CODE> and considers the system to not
have a working <CODE>vfork</CODE> if it detects any of them. It is not considered
to be an implementation error if a child's invocation of <CODE>signal</CODE>
modifies the parent's signal handler, since child processes rarely change
their signal handlers.
<P>
Since this macro defines <CODE>vfork</CODE> only for backward compatibility with
previous versions of @command{autoconf} you're encouraged to define it
yourself in new code:
<PRE>
#if !HAVE_WORKING_VFORK
# define vfork fork
#endif
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_FSEEKO</B>
<DD><A NAME="IDX243"></A>
<A NAME="IDX244"></A>
<A NAME="IDX245"></A>
<A NAME="IDX246"></A>
If the <CODE>fseeko</CODE> function is available, define <CODE>HAVE_FSEEKO</CODE>.
Define <CODE>_LARGEFILE_SOURCE</CODE> if necessary.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_GETGROUPS</B>
<DD><A NAME="IDX247"></A>
<A NAME="IDX248"></A>
<A NAME="IDX249"></A>
<A NAME="IDX250"></A>
If the <CODE>getgroups</CODE> function is available and works (unlike on
Ultrix 4.3, where <SAMP>`getgroups (0, 0)'</SAMP> always fails), define
<CODE>HAVE_GETGROUPS</CODE>. Set <CODE>GETGROUPS_LIBS</CODE> to any libraries
needed to get that function. This macro runs <CODE>AC_TYPE_GETGROUPS</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_GETLOADAVG</B>
<DD><A NAME="IDX251"></A>
<A NAME="IDX252"></A>
<A NAME="IDX253"></A>
<A NAME="IDX254"></A>
<A NAME="IDX255"></A>
<A NAME="IDX256"></A>
<A NAME="IDX257"></A>
<A NAME="IDX258"></A>
<A NAME="IDX259"></A>
<A NAME="IDX260"></A>
<A NAME="IDX261"></A>
<A NAME="IDX262"></A>
<A NAME="IDX263"></A>
<A NAME="IDX264"></A>
<A NAME="IDX265"></A>
<A NAME="IDX266"></A>
Check how to get the system load averages. If the system has the
<CODE>getloadavg</CODE> function, define <CODE>HAVE_GETLOADAVG</CODE>, and set
<CODE>GETLOADAVG_LIBS</CODE> to any libraries needed to get that function.
Also add <CODE>GETLOADAVG_LIBS</CODE> to <CODE>LIBS</CODE>.
<P>
Otherwise, require an <CODE>AC_LIBOBJ</CODE> replacement (<TT>`getloadavg.c'</TT>)
of <SAMP>`getloadavg'</SAMP>, and possibly define several other C preprocessor
macros and output variables:
<OL>
<LI>
Define <CODE>C_GETLOADAVG</CODE>.
<LI>
Define <CODE>SVR4</CODE>, <CODE>DGUX</CODE>, <CODE>UMAX</CODE>, or <CODE>UMAX4_3</CODE> if on
those systems.
<LI>
If <TT>`nlist.h'</TT> is found, define <CODE>NLIST_STRUCT</CODE>.
<LI>
If <SAMP>`struct nlist'</SAMP> has an <SAMP>`n_un.n_name'</SAMP> member, define
<CODE>HAVE_STRUCT_NLIST_N_UN_N_NAME</CODE>. The obsolete symbol
<CODE>NLIST_NAME_UNION</CODE> is still defined, but do not depend upon it.
<LI>
Programs may need to be installed setgid (or setuid) for
<CODE>getloadavg</CODE> to work. In this case, define
<CODE>GETLOADAVG_PRIVILEGED</CODE>, set the output variable <CODE>NEED_SETGID</CODE>
to <SAMP>`true'</SAMP> (and otherwise to <SAMP>`false'</SAMP>), and set
<CODE>KMEM_GROUP</CODE> to the name of the group that should own the installed
program.
</OL>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_GETMNTENT</B>
<DD><A NAME="IDX267"></A>
<A NAME="IDX268"></A>
<A NAME="IDX269"></A>
<A NAME="IDX270"></A>
Check for <CODE>getmntent</CODE> in the <TT>`sun'</TT>, <TT>`seq'</TT>, and <TT>`gen'</TT>
libraries, for Irix 4, PTX, and Unixware, respectively. Then, if
<CODE>getmntent</CODE> is available, define <CODE>HAVE_GETMNTENT</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_GETPGRP</B>
<DD><A NAME="IDX271"></A>
<A NAME="IDX272"></A>
<A NAME="IDX273"></A>
<A NAME="IDX274"></A>
<A NAME="IDX275"></A>
Define <CODE>GETPGRP_VOID</CODE> if it is an error to pass 0 to
<CODE>getpgrp</CODE>; this is the POSIX.1 behavior. On older BSD
systems, you must pass 0 to <CODE>getpgrp</CODE>, as it takes an argument and
behaves like POSIX.1's <CODE>getpgid</CODE>.
<PRE>
#if GETPGRP_VOID
pid = getpgrp ();
#else
pid = getpgrp (0);
#endif
</PRE>
<P>
This macro does not check whether
<CODE>getpgrp</CODE> exists at all; if you need to work in that situation,
first call <CODE>AC_CHECK_FUNC</CODE> for <CODE>getpgrp</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK</B>
<DD><A NAME="IDX276"></A>
<A NAME="IDX277"></A>
<A NAME="IDX278"></A>
<A NAME="IDX279"></A>
If <TT>`link'</TT> is a symbolic link, then <CODE>lstat</CODE> should treat
<TT>`link/'</TT> the same as <TT>`link/.'</TT>. However, many older
<CODE>lstat</CODE> implementations incorrectly ignore trailing slashes.
<P>
It is safe to assume that if <CODE>lstat</CODE> incorrectly ignores
trailing slashes, then other symbolic-link-aware functions like
<CODE>unlink</CODE> and <CODE>unlink</CODE> also incorrectly ignore trailing slashes.
<P>
If <CODE>lstat</CODE> behaves properly, define
<CODE>LSTAT_FOLLOWS_SLASHED_SYMLINK</CODE>, otherwise require an
<CODE>AC_LIBOBJ</CODE> replacement of <CODE>lstat</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_MALLOC</B>
<DD><A NAME="IDX280"></A>
<A NAME="IDX281"></A>
<A NAME="IDX282"></A>
If the <CODE>malloc</CODE> works correctly (<SAMP>`malloc (0)'</SAMP> returns a valid
pointer), define <CODE>HAVE_MALLOC</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_MEMCMP</B>
<DD><A NAME="IDX283"></A>
<A NAME="IDX284"></A>
<A NAME="IDX285"></A>
<A NAME="IDX286"></A>
If the <CODE>memcmp</CODE> function is not available, or does not work on
8-bit data (like the one on SunOS 4.1.3), or fails when comparing 16
bytes or more and with at least one buffer not starting on a 4-byte
boundary (such as the one on NeXT x86 OpenStep), require an
<CODE>AC_LIBOBJ</CODE> replacement for <SAMP>`memcmp'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_MKTIME</B>
<DD><A NAME="IDX287"></A>
<A NAME="IDX288"></A>
<A NAME="IDX289"></A>
<A NAME="IDX290"></A>
If the <CODE>mktime</CODE> function is not available, or does not work
correctly, require an <CODE>AC_LIBOBJ</CODE> replacement for <SAMP>`mktime'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_MMAP</B>
<DD><A NAME="IDX291"></A>
<A NAME="IDX292"></A>
<A NAME="IDX293"></A>
<A NAME="IDX294"></A>
If the <CODE>mmap</CODE> function exists and works correctly, define
<CODE>HAVE_MMAP</CODE>. Only checks private fixed mapping of already-mapped
memory.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_OBSTACK</B>
<DD><A NAME="IDX295"></A>
<A NAME="IDX296"></A>
<A NAME="IDX297"></A>
<A NAME="IDX298"></A>
If the obstacks are found, define <CODE>HAVE_OBSTACK</CODE>, else require an
<CODE>AC_LIBOBJ</CODE> replacement for <SAMP>`obstack'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_SELECT_ARGTYPES</B>
<DD><A NAME="IDX299"></A>
<A NAME="IDX300"></A>
<A NAME="IDX301"></A>
<A NAME="IDX302"></A>
<A NAME="IDX303"></A>
<A NAME="IDX304"></A>
Determines the correct type to be passed for each of the
<CODE>select</CODE> function's arguments, and defines those types
in <CODE>SELECT_TYPE_ARG1</CODE>, <CODE>SELECT_TYPE_ARG234</CODE>, and
<CODE>SELECT_TYPE_ARG5</CODE> respectively. <CODE>SELECT_TYPE_ARG1</CODE> defaults
to <SAMP>`int'</SAMP>, <CODE>SELECT_TYPE_ARG234</CODE> defaults to <SAMP>`int *'</SAMP>,
and <CODE>SELECT_TYPE_ARG5</CODE> defaults to <SAMP>`struct timeval *'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_SETPGRP</B>
<DD><A NAME="IDX305"></A>
<A NAME="IDX306"></A>
<A NAME="IDX307"></A>
<A NAME="IDX308"></A>
If <CODE>setpgrp</CODE> takes no argument (the POSIX.1 version), define
<CODE>SETPGRP_VOID</CODE>. Otherwise, it is the BSD version, which takes
two process IDs as arguments. This macro does not check whether
<CODE>setpgrp</CODE> exists at all; if you need to work in that situation,
first call <CODE>AC_CHECK_FUNC</CODE> for <CODE>setpgrp</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_STAT</B>
<DD><A NAME="IDX309"></A>
<DT><U>Macro:</U> <B>AC_FUNC_LSTAT</B>
<DD><A NAME="IDX310"></A>
<A NAME="IDX311"></A>
<A NAME="IDX312"></A>
<A NAME="IDX313"></A>
<A NAME="IDX314"></A>
<A NAME="IDX315"></A>
<A NAME="IDX316"></A>
Determine whether <CODE>stat</CODE> or <CODE>lstat</CODE> have the bug that it
succeeds when given the zero-length file name argument. The <CODE>stat</CODE>
and <CODE>lstat</CODE> from SunOS 4.1.4 and the Hurd (as of 1998-11-01) do
this.
<P>
If it does, then define <CODE>HAVE_STAT_EMPTY_STRING_BUG</CODE> (or
<CODE>HAVE_LSTAT_EMPTY_STRING_BUG</CODE>) and ask for an <CODE>AC_LIBOBJ</CODE>
replacement of it.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_SETVBUF_REVERSED</B>
<DD><A NAME="IDX317"></A>
<A NAME="IDX318"></A>
<A NAME="IDX319"></A>
<A NAME="IDX320"></A>
If <CODE>setvbuf</CODE> takes the buffering type as its second argument and
the buffer pointer as the third, instead of the other way around, define
<CODE>SETVBUF_REVERSED</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_STRCOLL</B>
<DD><A NAME="IDX321"></A>
<A NAME="IDX322"></A>
<A NAME="IDX323"></A>
<A NAME="IDX324"></A>
If the <CODE>strcoll</CODE> function exists and works correctly, define
<CODE>HAVE_STRCOLL</CODE>. This does a bit more than
<SAMP>`AC_CHECK_FUNCS(strcoll)'</SAMP>, because some systems have incorrect
definitions of <CODE>strcoll</CODE> that should not be used.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_STRTOD</B>
<DD><A NAME="IDX325"></A>
<A NAME="IDX326"></A>
<A NAME="IDX327"></A>
<A NAME="IDX328"></A>
If the <CODE>strtod</CODE> function does not exist or doesn't work correctly,
ask for an <CODE>AC_LIBOBJ</CODE> replacement of <SAMP>`strtod'</SAMP>. In this case,
because <TT>`strtod.c'</TT> is likely to need <SAMP>`pow'</SAMP>, set the output
variable <CODE>POW_LIB</CODE> to the extra library needed.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_STRERROR_R</B>
<DD><A NAME="IDX329"></A>
<A NAME="IDX330"></A>
<A NAME="IDX331"></A>
<A NAME="IDX332"></A>
<A NAME="IDX333"></A>
<A NAME="IDX334"></A>
If <CODE>strerror_r</CODE> is available, define <CODE>HAVE_STRERROR_R</CODE>, and if
it is declared, define <CODE>HAVE_DECL_STRERROR_R</CODE>. If it returns a
<CODE>char *</CODE> message, define <CODE>STRERROR_R_CHAR_P</CODE>; otherwise it
returns an <CODE>int</CODE> error number. The Thread-Safe Functions option of
POSIX-200X requires <CODE>strerror_r</CODE> to return <CODE>int</CODE>, but
many systems (including, for example, version 2.2.4 of the GNU C
Library) return a <CODE>char *</CODE> value that is not necessarily equal to
the buffer argument.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_STRFTIME</B>
<DD><A NAME="IDX335"></A>
<A NAME="IDX336"></A>
<A NAME="IDX337"></A>
<A NAME="IDX338"></A>
Check for <CODE>strftime</CODE> in the <TT>`intl'</TT> library, for SCO UNIX.
Then, if <CODE>strftime</CODE> is available, define <CODE>HAVE_STRFTIME</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_STRNLEN</B>
<DD><A NAME="IDX339"></A>
<A NAME="IDX340"></A>
<A NAME="IDX341"></A>
<A NAME="IDX342"></A>
Check for a working <CODE>strnlen</CODE>, and ask for its replacement. Some
architectures are know to provide broken versions of <CODE>strnlen</CODE>, such
as AIX 4.3.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_UTIME_NULL</B>
<DD><A NAME="IDX343"></A>
<A NAME="IDX344"></A>
<A NAME="IDX345"></A>
<A NAME="IDX346"></A>
If <SAMP>`utime(<VAR>file</VAR>, NULL)'</SAMP> sets <VAR>file</VAR>'s timestamp to
the present, define <CODE>HAVE_UTIME_NULL</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_VPRINTF</B>
<DD><A NAME="IDX347"></A>
<A NAME="IDX348"></A>
<A NAME="IDX349"></A>
<A NAME="IDX350"></A>
<A NAME="IDX351"></A>
If <CODE>vprintf</CODE> is found, define <CODE>HAVE_VPRINTF</CODE>. Otherwise, if
<CODE>_doprnt</CODE> is found, define <CODE>HAVE_DOPRNT</CODE>. (If <CODE>vprintf</CODE>
is available, you may assume that <CODE>vfprintf</CODE> and <CODE>vsprintf</CODE>
are also available.)
</DL>
<H3><A NAME="SEC47" HREF="autoconf_toc.html#TOC47">Generic Function Checks</A></H3>
<P>
These macros are used to find functions not covered by the "particular"
test macros. If the functions might be in libraries other than the
default C library, first call <CODE>AC_CHECK_LIB</CODE> for those libraries.
If you need to check the behavior of a function as well as find out
whether it is present, you have to write your own test for
it (see section <A HREF="autoconf.html#SEC68">Writing Tests</A>).
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_FUNC</B> <I>(<VAR>function</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX352"></A>
<A NAME="IDX353"></A>
If C function <VAR>function</VAR> is available, run shell commands
<VAR>action-if-found</VAR>, otherwise <VAR>action-if-not-found</VAR>. If you just
want to define a symbol if the function is available, consider using
<CODE>AC_CHECK_FUNCS</CODE> instead. This macro checks for functions with C
linkage even when <CODE>AC_LANG(C++)</CODE> has been called, since C is more
standardized than C++. (see section <A HREF="autoconf.html#SEC78">Language Choice</A>, for more information
about selecting the language for checks.)
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_FUNCS</B> <I>(<VAR>function</VAR>..., @ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX354"></A>
<A NAME="IDX355"></A>
<A NAME="IDX356"></A>
For each <VAR>function</VAR> in the whitespace-separated argument list,
define <CODE>HAVE_<VAR>function</VAR></CODE> (in all capitals) if it is available.
If <VAR>action-if-found</VAR> is given, it is additional shell code to
execute when one of the functions is found. You can give it a value of
<SAMP>`break'</SAMP> to break out of the loop on the first match. If
<VAR>action-if-not-found</VAR> is given, it is executed when one of the
functions is not found.
</DL>
<P>
Autoconf follows a philosophy that was formed over the years by those
who have struggled for portability: isolate the portability issues in
specific files, and then program as if you were in a POSIX
environment. Some functions may be missing or unfixable, and your
package must be ready to replace them.
<P>
Use the first three of the following macros to specify a function to be
replaced, and the last one (<CODE>AC_REPLACE_FUNCS</CODE>) to check for and
replace the function if needed.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_LIBOBJ</B> <I>(<VAR>function</VAR>)</I>
<DD><A NAME="IDX357"></A>
<A NAME="IDX358"></A>
<A NAME="IDX359"></A>
Specify that <SAMP>`<VAR>function</VAR>.c'</SAMP> must be included in the executables
to replace a missing or broken implementation of <VAR>function</VAR>.
<P>
Technically, it adds <SAMP>`<VAR>function</VAR>.$ac_objext'</SAMP> to the output
variable <CODE>LIBOBJS</CODE> and calls <CODE>AC_LIBSOURCE</CODE> for
<SAMP>`<VAR>function</VAR>.c'</SAMP>. You should not directly change <CODE>LIBOBJS</CODE>,
since this is not traceable.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_LIBSOURCE</B> <I>(<VAR>file</VAR>)</I>
<DD><A NAME="IDX360"></A>
<A NAME="IDX361"></A>
Specify that <VAR>file</VAR> might be needed to compile the project. If you
need to know what files might be needed by a <TT>`configure.ac'</TT>, you
should trace <CODE>AC_LIBSOURCE</CODE>. <VAR>file</VAR> must be a literal.
<P>
This macro is called automatically from <CODE>AC_LIBOBJ</CODE>, but you must
call it explicitly if you pass a shell variable to <CODE>AC_LIBOBJ</CODE>. In
that case, since shell variables cannot be traced statically, you must
pass to <CODE>AC_LIBSOURCE</CODE> any possible files that the shell variable
might cause <CODE>AC_LIBOBJ</CODE> to need. For example, if you want to pass
a variable <CODE>$foo_or_bar</CODE> to <CODE>AC_LIBOBJ</CODE> that holds either
<CODE>"foo"</CODE> or <CODE>"bar"</CODE>, you should do:
<PRE>
AC_LIBSOURCE(foo.c)
AC_LIBSOURCE(bar.c)
AC_LIBOBJ($foo_or_bar)
</PRE>
<P>
There is usually a way to avoid this, however, and you are encouraged to
simply call <CODE>AC_LIBOBJ</CODE> with literal arguments.
<P>
Note that this macro replaces the obsolete <CODE>AC_LIBOBJ_DECL</CODE>, with
slightly different semantics: the old macro took the function name,
e.g. <CODE>foo</CODE>, as its argument rather than the file name.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_LIBSOURCES</B> <I>(<VAR>files</VAR>)</I>
<DD><A NAME="IDX362"></A>
<A NAME="IDX363"></A>
Like <CODE>AC_LIBSOURCE</CODE>, but accepts one or more <VAR>files</VAR> in a
comma-separated M4 list. Thus, the above example might be rewritten:
<PRE>
AC_LIBSOURCES([foo.c, bar.c])
AC_LIBOBJ($foo_or_bar)
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_REPLACE_FUNCS</B> <I>(<VAR>function</VAR>...)</I>
<DD><A NAME="IDX364"></A>
<A NAME="IDX365"></A>
<A NAME="IDX366"></A>
Like <CODE>AC_CHECK_FUNCS</CODE>, but uses <SAMP>`AC_LIBOBJ(<VAR>function</VAR>)'</SAMP> as
<VAR>action-if-not-found</VAR>. You can declare your replacement function by
enclosing the prototype in <SAMP>`#if !HAVE_<VAR>function</VAR>'</SAMP>. If the
system has the function, it probably declares it in a header file you
should be including, so you shouldn't redeclare it lest your declaration
conflict.
</DL>
<H2><A NAME="SEC48" HREF="autoconf_toc.html#TOC48">Header Files</A></H2>
<P>
<A NAME="IDX367"></A>
<P>
The following macros check for the presence of certain C header files.
If there is no macro specifically defined to check for a header file you need,
and you don't need to check for any special properties of
it, then you can use one of the general header-file check macros.
<H3><A NAME="SEC49" HREF="autoconf_toc.html#TOC49">Particular Header Checks</A></H3>
<P>
These macros check for particular system header files--whether they
exist, and in some cases whether they declare certain symbols.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_DIRENT</B>
<DD><A NAME="IDX368"></A>
<A NAME="IDX369"></A>
<A NAME="IDX370"></A>
<A NAME="IDX371"></A>
<A NAME="IDX372"></A>
<A NAME="IDX373"></A>
Check for the following header files. For the first one that is
found and defines <SAMP>`DIR'</SAMP>, define the listed C preprocessor macro:
<LI><TT>`dirent.h'</TT> </TD><TD> <CODE>HAVE_DIRENT_H</CODE>
<LI><TT>`sys/ndir.h'</TT> </TD><TD> <CODE>HAVE_SYS_NDIR_H</CODE>
<LI><TT>`sys/dir.h'</TT> </TD><TD> <CODE>HAVE_SYS_DIR_H</CODE>
<LI><TT>`ndir.h'</TT> </TD><TD> <CODE>HAVE_NDIR_H</CODE>
The directory-library declarations in your source code should look
something like the following:
<PRE>
#if HAVE_DIRENT_H
# include <dirent.h>
# define NAMLEN(dirent) strlen((dirent)->d_name)
#else
# define dirent direct
# define NAMLEN(dirent) (dirent)->d_namlen
# if HAVE_SYS_NDIR_H
# include <sys/ndir.h>
# endif
# if HAVE_SYS_DIR_H
# include <sys/dir.h>
# endif
# if HAVE_NDIR_H
# include <ndir.h>
# endif
#endif
</PRE>
Using the above declarations, the program would declare variables to be
of type <CODE>struct dirent</CODE>, not <CODE>struct direct</CODE>, and would access
the length of a directory entry name by passing a pointer to a
<CODE>struct dirent</CODE> to the <CODE>NAMLEN</CODE> macro.
This macro also checks for the SCO Xenix <TT>`dir'</TT> and <TT>`x'</TT> libraries.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_MAJOR</B>
<DD><A NAME="IDX374"></A>
<A NAME="IDX375"></A>
<A NAME="IDX376"></A>
<A NAME="IDX377"></A>
If <TT>`sys/types.h'</TT> does not define <CODE>major</CODE>, <CODE>minor</CODE>, and
<CODE>makedev</CODE>, but <TT>`sys/mkdev.h'</TT> does, define
<CODE>MAJOR_IN_MKDEV</CODE>; otherwise, if <TT>`sys/sysmacros.h'</TT> does, define
<CODE>MAJOR_IN_SYSMACROS</CODE>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_STAT</B>
<DD><A NAME="IDX378"></A>
<A NAME="IDX379"></A>
<A NAME="IDX380"></A>
If the macros <CODE>S_ISDIR</CODE>, <CODE>S_ISREG</CODE> et al. defined in
<TT>`sys/stat.h'</TT> do not work properly (returning false positives),
define <CODE>STAT_MACROS_BROKEN</CODE>. This is the case on Tektronix UTekV,
Amdahl UTS and Motorola System V/88.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_STDC</B>
<DD><A NAME="IDX381"></A>
<A NAME="IDX382"></A>
<A NAME="IDX383"></A>
Define <CODE>STDC_HEADERS</CODE> if the system has ANSI C header files.
Specifically, this macro checks for <TT>`stdlib.h'</TT>, <TT>`stdarg.h'</TT>,
<TT>`string.h'</TT>, and <TT>`float.h'</TT>; if the system has those, it
probably has the rest of the ANSI C header files. This macro also
checks whether <TT>`string.h'</TT> declares <CODE>memchr</CODE> (and thus
presumably the other <CODE>mem</CODE> functions), whether <TT>`stdlib.h'</TT>
declare <CODE>free</CODE> (and thus presumably <CODE>malloc</CODE> and other related
functions), and whether the <TT>`ctype.h'</TT> macros work on characters
with the high bit set, as ANSI C requires.
Use <CODE>STDC_HEADERS</CODE> instead of <CODE>__STDC__</CODE> to determine whether
the system has ANSI-compliant header files (and probably C library
functions) because many systems that have GCC do not have ANSI C
header files.
On systems without ANSI C headers, there is so much variation that
it is probably easier to declare the functions you use than to figure
out exactly what the system header files declare. Some systems contain
a mix of functions ANSI and BSD; some are mostly ANSI but
lack <SAMP>`memmove'</SAMP>; some define the BSD functions as macros in
<TT>`string.h'</TT> or <TT>`strings.h'</TT>; some have only the BSD
functions but <TT>`string.h'</TT>; some declare the memory functions in
<TT>`memory.h'</TT>, some in <TT>`string.h'</TT>; etc. It is probably
sufficient to check for one string function and one memory function; if
the library has the ANSI versions of those then it probably has
most of the others. If you put the following in <TT>`configure.ac'</TT>:
<PRE>
AC_HEADER_STDC
AC_CHECK_FUNCS(strchr memcpy)
</PRE>
then, in your code, you can put declarations like this:
<PRE>
#if STDC_HEADERS
# include <string.h>
#else
# if !HAVE_STRCHR
# define strchr index
# define strrchr rindex
# endif
char *strchr (), *strrchr ();
# if !HAVE_MEMCPY
# define memcpy(d, s, n) bcopy ((s), (d), (n))
# define memmove(d, s, n) bcopy ((s), (d), (n))
# endif
#endif
</PRE>
If you use a function like <CODE>memchr</CODE>, <CODE>memset</CODE>, <CODE>strtok</CODE>,
or <CODE>strspn</CODE>, which have no BSD equivalent, then macros won't
suffice; you must provide an implementation of each function. An easy
way to incorporate your implementations only when needed (since the ones
in system C libraries may be hand optimized) is to, taking <CODE>memchr</CODE>
for example, put it in <TT>`memchr.c'</TT> and use
<SAMP>`AC_REPLACE_FUNCS(memchr)'</SAMP>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_SYS_WAIT</B>
<DD><A NAME="IDX384"></A>
<A NAME="IDX385"></A>
<A NAME="IDX386"></A>
If <TT>`sys/wait.h'</TT> exists and is compatible with POSIX.1, define
<CODE>HAVE_SYS_WAIT_H</CODE>. Incompatibility can occur if <TT>`sys/wait.h'</TT>
does not exist, or if it uses the old BSD <CODE>union wait</CODE> instead
of <CODE>int</CODE> to store a status value. If <TT>`sys/wait.h'</TT> is not
POSIX.1 compatible, then instead of including it, define the
POSIX.1 macros with their usual interpretations. Here is an
example:
<PRE>
#include <sys/types.h>
#if HAVE_SYS_WAIT_H
# include <sys/wait.h>
#endif
#ifndef WEXITSTATUS
# define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
#endif
#ifndef WIFEXITED
# define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
#endif
</PRE>
</DL>
<A NAME="IDX387"></A>
<CODE>_POSIX_VERSION</CODE> is defined when <TT>`unistd.h'</TT> is included on
POSIX.1 systems. If there is no <TT>`unistd.h'</TT>, it is definitely
not a POSIX.1 system. However, some non-POSIX.1 systems do
have <TT>`unistd.h'</TT>.
The way to check if the system supports POSIX.1 is:
<PRE>
#if HAVE_UNISTD_H
# include <sys/types.h>
# include <unistd.h>
#endif
#ifdef _POSIX_VERSION
/* Code for POSIX.1 systems. */
#endif
</PRE>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_TIME</B>
<DD><A NAME="IDX388"></A>
<A NAME="IDX389"></A>
<A NAME="IDX390"></A>
If a program may include both <TT>`time.h'</TT> and <TT>`sys/time.h'</TT>,
define <CODE>TIME_WITH_SYS_TIME</CODE>. On some older systems,
<TT>`sys/time.h'</TT> includes <TT>`time.h'</TT>, but <TT>`time.h'</TT> is not
protected against multiple inclusion, so programs should not explicitly
include both files. This macro is useful in programs that use, for
example, <CODE>struct timeval</CODE> or <CODE>struct timezone</CODE> as well as
<CODE>struct tm</CODE>. It is best used in conjunction with
<CODE>HAVE_SYS_TIME_H</CODE>, which can be checked for using
<CODE>AC_CHECK_HEADERS(sys/time.h)</CODE>.
<PRE>
#if TIME_WITH_SYS_TIME
# include <sys/time.h>
# include <time.h>
#else
# if HAVE_SYS_TIME_H
# include <sys/time.h>
# else
# include <time.h>
# endif
#endif
</PRE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_TIOCGWINSZ</B>
<DD><A NAME="IDX391"></A>
<A NAME="IDX392"></A>
<A NAME="IDX393"></A>
If the use of <CODE>TIOCGWINSZ</CODE> requires <TT>`<sys/ioctl.h>'</TT>, then
define <CODE>GWINSZ_IN_SYS_IOCTL</CODE>. Otherwise <CODE>TIOCGWINSZ</CODE> can be
found in <TT>`<termios.h>'</TT>.
Use:
<PRE>
#if HAVE_TERMIOS_H
# include <termios.h>
#endif
#if GWINSZ_IN_SYS_IOCTL
# include <sys/ioctl.h>
#endif
</PRE>
</DL>
<H3><A NAME="SEC50" HREF="autoconf_toc.html#TOC50">Generic Header Checks</A></H3>
<P>
These macros are used to find system header files not covered by the
"particular" test macros. If you need to check the contents of a header
as well as find out whether it is present, you have to write your own
test for it (see section <A HREF="autoconf.html#SEC68">Writing Tests</A>).
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_HEADER</B> <I>(<VAR>header-file</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX394"></A>
<A NAME="IDX395"></A>
If the system header file <VAR>header-file</VAR> is usable, execute shell
commands <VAR>action-if-found</VAR>, otherwise execute
<VAR>action-if-not-found</VAR>. If you just want to define a symbol if the
header file is available, consider using <CODE>AC_CHECK_HEADERS</CODE>
instead.
<P>
The meaning of "usable" depends upon the content of <VAR>includes</VAR>:
<DL COMPACT>
<DT>if <VAR>includes</VAR> is empty
<DD>
check whether
<PRE>
<VAR>header-file</VAR>
</PRE>
can be <EM>preprocessed</EM> without error.
<DT>if <VAR>include</VAR> is set
<DD>
Check whether
<PRE>
<VAR>includes</VAR>
#include <<VAR>header-file</VAR>>
</PRE>
can be <EM>compiled</EM> without error. You may use
<CODE>AC_CHECK_HEADER</CODE> (and <CODE>AC_CHECK_HEADERS</CODE>) to check whether
two headers are compatible.
</DL>
<P>
You may pass any kind of dummy content for <VAR>includes</VAR>, such as a
single space, a comment, to check whether <VAR>header-file</VAR> compiles
with success.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_HEADERS</B> <I>(<VAR>header-file</VAR>..., @ovar{action-if-found}, @ovar{action-if-not-found}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX396"></A>
<A NAME="IDX397"></A>
<A NAME="IDX398"></A>
For each given system header file <VAR>header-file</VAR> in the
whitespace-separated argument list that exists, define
<CODE>HAVE_<VAR>header-file</VAR></CODE> (in all capitals). If <VAR>action-if-found</VAR>
is given, it is additional shell code to execute when one of the header
files is found. You can give it a value of <SAMP>`break'</SAMP> to break out of
the loop on the first match. If <VAR>action-if-not-found</VAR> is given, it
is executed when one of the header files is not found.
<P>
Be sure to read the documentation of <CODE>AC_CHECK_HEADER</CODE> to
understand the influence of <VAR>includes</VAR>.
</DL>
<H2><A NAME="SEC51" HREF="autoconf_toc.html#TOC51">Declarations</A></H2>
<P>
<A NAME="IDX399"></A>
<P>
The following macros check for the declaration of variables and
functions. If there is no macro specifically defined to check for a
symbol you need, then you can use the general macros (see section <A HREF="autoconf.html#SEC53">Generic Declaration Checks</A>) or, for more complex tests, you may use
<CODE>AC_TRY_COMPILE</CODE> (see section <A HREF="autoconf.html#SEC70">Examining Syntax</A>).
<H3><A NAME="SEC52" HREF="autoconf_toc.html#TOC52">Particular Declaration Checks</A></H3>
<P>
The following macros check for certain declarations.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_DECL_SYS_SIGLIST</B>
<DD><A NAME="IDX400"></A>
<A NAME="IDX401"></A>
<A NAME="IDX402"></A>
Define <CODE>SYS_SIGLIST_DECLARED</CODE> if the variable <CODE>sys_siglist</CODE>
is declared in a system header file, either <TT>`signal.h'</TT> or
<TT>`unistd.h'</TT>.
</DL>
<H3><A NAME="SEC53" HREF="autoconf_toc.html#TOC53">Generic Declaration Checks</A></H3>
<P>
These macros are used to find declarations not covered by the "particular"
test macros.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_DECL</B> <I>(<VAR>symbol</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX403"></A>
<A NAME="IDX404"></A>
If <VAR>symbol</VAR> (a function or a variable) is not declared in
<VAR>includes</VAR> and a declaration is needed, run the shell commands
<VAR>action-if-not-found</VAR>, otherwise <VAR>action-if-found</VAR>. If no
<VAR>includes</VAR> are specified, the default includes are used
(see section <A HREF="autoconf.html#SEC38">Default Includes</A>).
<P>
This macro actually tests whether it is valid to use <VAR>symbol</VAR> as an
r-value, not if it is really declared, because it is much safer to avoid
introducing extra declarations when they are not needed.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_DECLS</B> <I>(<VAR>symbols</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX405"></A>
<A NAME="IDX406"></A>
<A NAME="IDX407"></A>
For each of the <VAR>symbols</VAR> (<EM>comma</EM>-separated list), define
<CODE>HAVE_DECL_<VAR>symbol</VAR></CODE> (in all capitals) to <SAMP>`1'</SAMP> if
<VAR>symbol</VAR> is declared, otherwise to <SAMP>`0'</SAMP>. If
<VAR>action-if-not-found</VAR> is given, it is additional shell code to
execute when one of the function declarations is needed, otherwise
<VAR>action-if-found</VAR> is executed.
<P>
This macro uses an m4 list as first argument:
<PRE>
AC_CHECK_DECLS(strdup)
AC_CHECK_DECLS([strlen])
AC_CHECK_DECLS([malloc, realloc, calloc, free])
</PRE>
<P>
Unlike the other <SAMP>`AC_CHECK_*S'</SAMP> macros, when a <VAR>symbol</VAR> is not
declared, <CODE>HAVE_DECL_<VAR>symbol</VAR></CODE> is defined to <SAMP>`0'</SAMP> instead
of leaving <CODE>HAVE_DECL_<VAR>symbol</VAR></CODE> undeclared. When you are
<EM>sure</EM> that the check was performed, use
<CODE>HAVE_DECL_<VAR>symbol</VAR></CODE> just like any other result of Autoconf:
<PRE>
#if !HAVE_DECL_SYMBOL
extern char *symbol;
#endif
</PRE>
<P>
If the test may have not been performed, however, because it is safer
<EM>not</EM> to declare a symbol than to use a declaration that conflicts
with the system's one, you should use:
<PRE>
#if defined HAVE_DECL_MALLOC && !HAVE_DECL_MALLOC
char *malloc (size_t *s);
#endif
</PRE>
<P>
You fall into the second category only in extreme situations: either
your files may be used without being configured, or they are used during
the configuration. In most cases the traditional approach is enough.
</DL>
<H2><A NAME="SEC54" HREF="autoconf_toc.html#TOC54">Structures</A></H2>
<P>
<A NAME="IDX408"></A>
<P>
The following macros check for the presence of certain members in C
structures. If there is no macro specifically defined to check for a
member you need, then you can use the general structure-member macro
(see section <A HREF="autoconf.html#SEC56">Generic Structure Checks</A>) or, for more complex tests, you may use
<CODE>AC_TRY_COMPILE</CODE> (see section <A HREF="autoconf.html#SEC70">Examining Syntax</A>).
<H3><A NAME="SEC55" HREF="autoconf_toc.html#TOC55">Particular Structure Checks</A></H3>
<P>
The following macros check for certain structures or structure members.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_STRUCT_ST_BLKSIZE</B>
<DD><A NAME="IDX409"></A>
<A NAME="IDX410"></A>
<A NAME="IDX411"></A>
<A NAME="IDX412"></A>
If <CODE>struct stat</CODE> contains an <CODE>st_blksize</CODE> member, define
<CODE>HAVE_STRUCT_STAT_ST_BLKSIZE</CODE>. The former name,
<CODE>HAVE_ST_BLKSIZE</CODE> is to be avoided, as its support will cease in
the future. This macro is obsoleted, and should be replaced by
<PRE>
AC_CHECK_MEMBERS([struct stat.st_blksize])
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_STRUCT_ST_BLOCKS</B>
<DD><A NAME="IDX413"></A>
<A NAME="IDX414"></A>
<A NAME="IDX415"></A>
<A NAME="IDX416"></A>
<A NAME="IDX417"></A>
If <CODE>struct stat</CODE> contains an <CODE>st_blocks</CODE> member, define
<CODE>HAVE_STRUCT STAT_ST_BLOCKS</CODE>. Otherwise, require an
<CODE>AC_LIBOBJ</CODE> replacement of <SAMP>`fileblocks'</SAMP>. The former name,
<CODE>HAVE_ST_BLOCKS</CODE> is to be avoided, as its support will cease in the
future.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_STRUCT_ST_RDEV</B>
<DD><A NAME="IDX418"></A>
<A NAME="IDX419"></A>
<A NAME="IDX420"></A>
<A NAME="IDX421"></A>
If <CODE>struct stat</CODE> contains an <CODE>st_rdev</CODE> member, define
<CODE>HAVE_STRUCT_STAT_ST_RDEV</CODE>. The former name for this macro,
<CODE>HAVE_ST_RDEV</CODE>, is to be avoided as it will cease to be supported
in the future. Actually, even the new macro is obsolete, and should be
replaced by:
<PRE>
AC_CHECK_MEMBERS([struct stat.st_rdev])
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_STRUCT_TM</B>
<DD><A NAME="IDX422"></A>
<A NAME="IDX423"></A>
<A NAME="IDX424"></A>
If <TT>`time.h'</TT> does not define <CODE>struct tm</CODE>, define
<CODE>TM_IN_SYS_TIME</CODE>, which means that including <TT>`sys/time.h'</TT>
had better define <CODE>struct tm</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_STRUCT_TIMEZONE</B>
<DD><A NAME="IDX425"></A>
<A NAME="IDX426"></A>
<A NAME="IDX427"></A>
<A NAME="IDX428"></A>
Figure out how to get the current timezone. If <CODE>struct tm</CODE> has a
<CODE>tm_zone</CODE> member, define <CODE>HAVE_STRUCT_TM_TM_ZONE</CODE> (and the
obsoleted <CODE>HAVE_TM_ZONE</CODE>). Otherwise, if the external array
<CODE>tzname</CODE> is found, define <CODE>HAVE_TZNAME</CODE>.
</DL>
<H3><A NAME="SEC56" HREF="autoconf_toc.html#TOC56">Generic Structure Checks</A></H3>
<P>
These macros are used to find structure members not covered by the
"particular" test macros.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_MEMBER</B> <I>(<VAR>aggregate</VAR>.<VAR>member</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX429"></A>
<A NAME="IDX430"></A>
Check whether <VAR>member</VAR> is a member of the aggregate <VAR>aggregate</VAR>.
If no <VAR>includes</VAR> are specified, the default includes are used
(see section <A HREF="autoconf.html#SEC38">Default Includes</A>).
<PRE>
AC_CHECK_MEMBER(struct passwd.pw_gecos,,
[AC_MSG_ERROR([We need `passwd.pw_gecos'!])],
[#include <pwd.h>])
</PRE>
<P>
You can use this macro for sub-members:
<PRE>
AC_CHECK_MEMBER(struct top.middle.bot)
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_MEMBERS</B> <I>(<VAR>members</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX431"></A>
<A NAME="IDX432"></A>
Check for the existence of each <SAMP>`<VAR>aggregate</VAR>.<VAR>member</VAR>'</SAMP> of
<VAR>members</VAR> using the previous macro. When <VAR>member</VAR> belongs to
<VAR>aggregate</VAR>, define <CODE>HAVE_<VAR>aggregate</VAR>_<VAR>member</VAR></CODE> (in all
capitals, with spaces and dots replaced by underscores).
<P>
This macro uses m4 lists:
<PRE>
AC_CHECK_MEMBERS([struct stat.st_rdev, struct stat.st_blksize])
</PRE>
</DL>
<H2><A NAME="SEC57" HREF="autoconf_toc.html#TOC57">Types</A></H2>
<P>
The following macros check for C types, either builtin or typedefs. If
there is no macro specifically defined to check for a type you need, and
you don't need to check for any special properties of it, then you can
use a general type-check macro.
<H3><A NAME="SEC58" HREF="autoconf_toc.html#TOC58">Particular Type Checks</A></H3>
<P>
These macros check for particular C types in <TT>`sys/types.h'</TT>,
<TT>`stdlib.h'</TT> and others, if they exist.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TYPE_GETGROUPS</B>
<DD><A NAME="IDX433"></A>
<A NAME="IDX434"></A>
<A NAME="IDX435"></A>
Define <CODE>GETGROUPS_T</CODE> to be whichever of <CODE>gid_t</CODE> or <CODE>int</CODE>
is the base type of the array argument to <CODE>getgroups</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TYPE_MODE_T</B>
<DD><A NAME="IDX436"></A>
<A NAME="IDX437"></A>
<A NAME="IDX438"></A>
Equivalent to <SAMP>`AC_CHECK_TYPE(mode_t, int)'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TYPE_OFF_T</B>
<DD><A NAME="IDX439"></A>
<A NAME="IDX440"></A>
<A NAME="IDX441"></A>
Equivalent to <SAMP>`AC_CHECK_TYPE(off_t, long)'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TYPE_PID_T</B>
<DD><A NAME="IDX442"></A>
<A NAME="IDX443"></A>
<A NAME="IDX444"></A>
Equivalent to <SAMP>`AC_CHECK_TYPE(pid_t, int)'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TYPE_SIGNAL</B>
<DD><A NAME="IDX445"></A>
<A NAME="IDX446"></A>
<A NAME="IDX447"></A>
If <TT>`signal.h'</TT> declares <CODE>signal</CODE> as returning a pointer to a
function returning <CODE>void</CODE>, define <CODE>RETSIGTYPE</CODE> to be
<CODE>void</CODE>; otherwise, define it to be <CODE>int</CODE>.
<P>
Define signal handlers as returning type <CODE>RETSIGTYPE</CODE>:
<PRE>
RETSIGTYPE
hup_handler ()
{
...
}
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TYPE_SIZE_T</B>
<DD><A NAME="IDX448"></A>
<A NAME="IDX449"></A>
<A NAME="IDX450"></A>
Equivalent to <SAMP>`AC_CHECK_TYPE(size_t, unsigned)'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TYPE_UID_T</B>
<DD><A NAME="IDX451"></A>
<A NAME="IDX452"></A>
<A NAME="IDX453"></A>
<A NAME="IDX454"></A>
If <CODE>uid_t</CODE> is not defined, define <CODE>uid_t</CODE> to be <CODE>int</CODE> and
<CODE>gid_t</CODE> to be <CODE>int</CODE>.
</DL>
<H3><A NAME="SEC59" HREF="autoconf_toc.html#TOC59">Generic Type Checks</A></H3>
<P>
These macros are used to check for types not covered by the "particular"
test macros.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_TYPE</B> <I>(<VAR>type</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX455"></A>
<A NAME="IDX456"></A>
Check whether <VAR>type</VAR> is defined. It may be a compiler builtin type
or defined by the <VAR>includes</VAR> (see section <A HREF="autoconf.html#SEC38">Default Includes</A>).
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_TYPES</B> <I>(<VAR>types</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX457"></A>
<A NAME="IDX458"></A>
For each <VAR>type</VAR> of the <VAR>types</VAR> that is defined, define
<CODE>HAVE_<VAR>type</VAR></CODE> (in all capitals). If no <VAR>includes</VAR> are
specified, the default includes are used (see section <A HREF="autoconf.html#SEC38">Default Includes</A>). If
<VAR>action-if-found</VAR> is given, it is additional shell code to execute
when one of the types is found. If <VAR>action-if-not-found</VAR> is given,
it is executed when one of the types is not found.
<P>
This macro uses m4 lists:
<PRE>
AC_CHECK_TYPES(ptrdiff_t)
AC_CHECK_TYPES([unsigned long long, uintmax_t])
</PRE>
</DL>
<P>
Autoconf, up to 2.13, used to provide to another version of
<CODE>AC_CHECK_TYPE</CODE>, broken by design. In order to keep backward
compatibility, a simple heuristics, quite safe but not totally, is
implemented. In case of doubt, read the documentation of the former
<CODE>AC_CHECK_TYPE</CODE>, see section <A HREF="autoconf.html#SEC150">Obsolete Macros</A>.
<H2><A NAME="SEC60" HREF="autoconf_toc.html#TOC60">Compilers and Preprocessors</A></H2>
<P>
<A NAME="IDX459"></A>
All the tests for compilers (<CODE>AC_PROG_CC</CODE>, <CODE>AC_PROG_CXX</CODE>,
<CODE>AC_PROG_F77</CODE>) define the output variable <CODE>EXEEXT</CODE> based on
the output of the 1compiler, typically to the empty string if Unix and
<SAMP>`.exe'</SAMP> if Win32 or OS/2.
<P>
<A NAME="IDX460"></A>
They also define the output variable <CODE>OBJEXT</CODE> based on the
output of the compiler, after .c files have been excluded, typically
to <SAMP>`o'</SAMP> if Unix, <SAMP>`obj'</SAMP> if Win32.
<P>
If the compiler being used does not produce executables, they fail. If
the executables can't be run, and cross-compilation is not enabled, they
fail too. See section <A HREF="autoconf.html#SEC121">Manual Configuration</A>, for more on support for cross
compiling.
<H3><A NAME="SEC61" HREF="autoconf_toc.html#TOC61">Specific Compiler Characteristics</A></H3>
<P>
Some compilers exhibit different behaviors.
<DL COMPACT>
<DT>Static/Dynamic Expressions
<DD>
Autoconf relies on a trick to extract one bit of information from the C
compiler: using negative array sizes. For instance the following
excerpt of a C source demonstrates how to test whether <SAMP>`int'</SAMP>s are 4
bytes long:
<PRE>
int
main (void)
{
static int test_array [sizeof (int) == 4 ? 1 : -1];
test_array [0] = 0
return 0;
}
</PRE>
To our knowledge, there is a single compiler that does not support this
trick: the HP C compilers (the real one, not only the "bundled") on
HP-UX 11.00:
<PRE>
$ <KBD>cc -c -Ae +O2 +Onolimit conftest.c</KBD>
cc: "conftest.c": error 1879: Variable-length arrays cannot \
have static storage.
</PRE>
Autoconf works around this problem by casting <CODE>sizeof (int)</CODE> to
<CODE>long</CODE> before comparing it.
</DL>
<H3><A NAME="SEC62" HREF="autoconf_toc.html#TOC62">Generic Compiler Characteristics</A></H3>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_SIZEOF</B> <I>(<VAR>type</VAR>, @ovar{unused}, @dvar{includes, default-includes})</I>
<DD><A NAME="IDX461"></A>
<A NAME="IDX462"></A>
Define <CODE>SIZEOF_<VAR>type</VAR></CODE> (see section <A HREF="autoconf.html#SEC37">Standard Symbols</A>) to be the
size in bytes of <VAR>type</VAR>. If <SAMP>`type'</SAMP> is unknown, it gets a size
of 0. If no <VAR>includes</VAR> are specified, the default includes are used
(see section <A HREF="autoconf.html#SEC38">Default Includes</A>). If you provide <VAR>include</VAR>, make sure to
include <TT>`stdio.h'</TT> which is required for this macro to run.
<P>
This macro now works even when cross-compiling. The <VAR>unused</VAR>
argument was used when cross-compiling.
<P>
For example, the call
<PRE>
AC_CHECK_SIZEOF(int *)
</PRE>
<P>
defines <CODE>SIZEOF_INT_P</CODE> to be 8 on DEC Alpha AXP systems.
</DL>
<H3><A NAME="SEC63" HREF="autoconf_toc.html#TOC63">C Compiler Characteristics</A></H3>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_CC</B> <I>(@ovar{compiler-search-list})</I>
<DD><A NAME="IDX463"></A>
<A NAME="IDX464"></A>
<A NAME="IDX465"></A>
<A NAME="IDX466"></A>
Determine a C compiler to use. If <CODE>CC</CODE> is not already set in the
environment, check for <CODE>gcc</CODE> and <CODE>cc</CODE>, then for other C
compilers. Set output variable <CODE>CC</CODE> to the name of the compiler
found.
<P>
This macro may, however, be invoked with an optional first argument
which, if specified, must be a space separated list of C compilers to
search for. This just gives the user an opportunity to specify an
alternative search list for the C compiler. For example, if you didn't
like the default order, then you could invoke <CODE>AC_PROG_CC</CODE> like
this:
<PRE>
AC_PROG_CC(cl egcs gcc cc)
</PRE>
<P>
If using the GNU C compiler, set shell variable <CODE>GCC</CODE> to
<SAMP>`yes'</SAMP>. If output variable <CODE>CFLAGS</CODE> was not already set, set
it to @option{-g -O2} for the GNU C compiler (@option{-O2} on systems
where GCC does not accept @option{-g}), or @option{-g} for other compilers.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_CC_C_O</B>
<DD><A NAME="IDX467"></A>
<A NAME="IDX468"></A>
<A NAME="IDX469"></A>
If the C compiler does not accept the @option{-c} and @option{-o} options
simultaneously, define <CODE>NO_MINUS_C_MINUS_O</CODE>. This macro actually
tests both the compiler found by <CODE>AC_PROG_CC</CODE>, and, if different,
the first <CODE>cc</CODE> in the path. The test fails if one fails. This
macro was created for GNU Make to choose the default C compilation
rule.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_CC_STDC</B>
<DD><A NAME="IDX470"></A>
<A NAME="IDX471"></A>
<A NAME="IDX472"></A>
If the C compiler is not in ANSI C mode by default, try to add an
option to output variable <CODE>CC</CODE> to make it so. This macro tries
various options that select ANSI C on some system or another. It
considers the compiler to be in ANSI C mode if it handles function
prototypes correctly.
<P>
If you use this macro, you should check after calling it whether the C
compiler has been set to accept ANSI C; if not, the shell variable
<CODE>ac_cv_prog_cc_stdc</CODE> is set to <SAMP>`no'</SAMP>. If you wrote your source
code in ANSI C, you can make an un-ANSIfied copy of it by
using the program <CODE>ansi2knr</CODE>, which comes with Automake.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_CPP</B>
<DD><A NAME="IDX473"></A>
<A NAME="IDX474"></A>
<A NAME="IDX475"></A>
Set output variable <CODE>CPP</CODE> to a command that runs the
C preprocessor. If <SAMP>`$CC -E'</SAMP> doesn't work, <TT>`/lib/cpp'</TT> is used.
It is only portable to run <CODE>CPP</CODE> on files with a <TT>`.c'</TT>
extension.
<P>
If the current language is C (see section <A HREF="autoconf.html#SEC78">Language Choice</A>), many of the
specific test macros use the value of <CODE>CPP</CODE> indirectly by calling
<CODE>AC_TRY_CPP</CODE>, <CODE>AC_CHECK_HEADER</CODE>, <CODE>AC_EGREP_HEADER</CODE>, or
<CODE>AC_EGREP_CPP</CODE>.
<P>
Some preprocessors don't indicate missing include files by the error
status. For such preprocessors an internal variable is set that causes
other macros to check the standard error from the preprocessor and
consider the test failed if any warnings have been reported.
</DL>
<P>
The following macros check for C compiler or machine architecture
features. To check for characteristics not listed here, use
<CODE>AC_TRY_COMPILE</CODE> (see section <A HREF="autoconf.html#SEC70">Examining Syntax</A>) or <CODE>AC_TRY_RUN</CODE>
(see section <A HREF="autoconf.html#SEC72">Checking Run Time Behavior</A>)
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_BIGENDIAN</B> <I>(@ovar{action-if-true}, @ovar{action-if-false}, @ovar{action-if-unknown})</I>
<DD><A NAME="IDX476"></A>
<A NAME="IDX477"></A>
<A NAME="IDX478"></A>
<A NAME="IDX479"></A>
If words are stored with the most significant byte first (like Motorola
and SPARC CPUs), execute <VAR>action-if-true</VAR>. If words are stored with
the less significant byte first (like Intel and VAX CPUs), execute
<VAR>action-if-false</VAR>.
<P>
This macro runs a test-case if endianness cannot be determined from the
system header files. When cross-compiling the test-case is not run but
grep'ed for some magic values. <VAR>action-if-unknown</VAR> is executed if
the latter case fails to determine the byte sex of the host system.
<P>
The default for <VAR>action-if-true</VAR> is to define
<SAMP>`WORDS_BIGENDIAN'</SAMP>. The default for <VAR>action-if-false</VAR> is to do
nothing. And finally, the default for <VAR>action-if-unknown</VAR> is to
abort configure and tell the installer which variable he should preset
to bypass this test.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_CONST</B>
<DD><A NAME="IDX480"></A>
<A NAME="IDX481"></A>
<A NAME="IDX482"></A>
If the C compiler does not fully support the ANSI C qualifier
<CODE>const</CODE>, define <CODE>const</CODE> to be empty. Some C compilers that do
not define <CODE>__STDC__</CODE> do support <CODE>const</CODE>; some compilers that
define <CODE>__STDC__</CODE> do not completely support <CODE>const</CODE>. Programs
can simply use <CODE>const</CODE> as if every C compiler supported it; for
those that don't, the <TT>`Makefile'</TT> or configuration header file will
define it as empty.
<P>
Occasionally installers use a C++ compiler to compile C code, typically
because they lack a C compiler. This causes problems with <CODE>const</CODE>,
because C and C++ treat <CODE>const</CODE> differently. For example:
<PRE>
const int foo;
</PRE>
<P>
is valid in C but not in C++. These differences unfortunately cannot be
papered over by defining <CODE>const</CODE> to be empty.
<P>
If @command{autoconf} detects this situation, it leaves <CODE>const</CODE> alone,
as this generally yields better results in practice. However, using a
C++ compiler to compile C code is not recommended or supported, and
installers who run into trouble in this area should get a C compiler
like GCC to compile their C code.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_VOLATILE</B>
<DD><A NAME="IDX483"></A>
<A NAME="IDX484"></A>
<A NAME="IDX485"></A>
If the C compiler does not understand the keyword <CODE>volatile</CODE>,
define <CODE>volatile</CODE> to be empty. Programs can simply use
<CODE>volatile</CODE> as if every C compiler supported it; for those that do
not, the <TT>`Makefile'</TT> or configuration header will define it as
empty.
<P>
If the correctness of your program depends on the semantics of
<CODE>volatile</CODE>, simply defining it to be empty does, in a sense, break
your code. However, given that the compiler does not support
<CODE>volatile</CODE>, you are at its mercy anyway. At least your
program will compile, when it wouldn't before.
<P>
In general, the <CODE>volatile</CODE> keyword is a feature of ANSI C, so
you might expect that <CODE>volatile</CODE> is available only when
<CODE>__STDC__</CODE> is defined. However, Ultrix 4.3's native compiler does
support volatile, but does not defined <CODE>__STDC__</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_INLINE</B>
<DD><A NAME="IDX486"></A>
<A NAME="IDX487"></A>
<A NAME="IDX488"></A>
If the C compiler supports the keyword <CODE>inline</CODE>, do nothing.
Otherwise define <CODE>inline</CODE> to <CODE>__inline__</CODE> or <CODE>__inline</CODE>
if it accepts one of those, otherwise define <CODE>inline</CODE> to be empty.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_CHAR_UNSIGNED</B>
<DD><A NAME="IDX489"></A>
<A NAME="IDX490"></A>
<A NAME="IDX491"></A>
If the C type <CODE>char</CODE> is unsigned, define <CODE>__CHAR_UNSIGNED__</CODE>,
unless the C compiler predefines it.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_LONG_DOUBLE</B>
<DD><A NAME="IDX492"></A>
<A NAME="IDX493"></A>
<A NAME="IDX494"></A>
If the C compiler supports a working <CODE>long double</CODE> type with more
range or precision than the <CODE>double</CODE> type, define
<CODE>HAVE_LONG_DOUBLE</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_STRINGIZE</B>
<DD><A NAME="IDX495"></A>
<A NAME="IDX496"></A>
<A NAME="IDX497"></A>
If the C preprocessor supports the stringizing operator, define
<CODE>HAVE_STRINGIZE</CODE>. The stringizing operator is <SAMP>`#'</SAMP> and is
found in macros such as this:
<PRE>
#define x(y) #y
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_PROTOTYPES</B>
<DD><A NAME="IDX498"></A>
<A NAME="IDX499"></A>
<A NAME="IDX500"></A>
<A NAME="IDX501"></A>
<A NAME="IDX502"></A>
Check to see if function prototypes are understood by the compiler. If
so, define <CODE>PROTOTYPES</CODE> and <CODE>__PROTOTYPES</CODE>.
In the case the compiler does not handle
prototypes, you should use <CODE>ansi2knr</CODE>, which comes with the
Automake distribution, to unprotoize function definitions. For
function prototypes, you should first define <CODE>PARAMS</CODE>:
<PRE>
#ifndef PARAMS
# if PROTOTYPES
# define PARAMS(protos) protos
# else /* no PROTOTYPES */
# define PARAMS(protos) ()
# endif /* no PROTOTYPES */
#endif
</PRE>
<P>
then use it this way:
<PRE>
size_t my_strlen PARAMS ((const char *));
</PRE>
</DL>
<P>
This macro also defines <CODE>__PROTOTYPES</CODE>; this is for the benefit of
header files that cannot use macros that infringe on user name space.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_GCC_TRADITIONAL</B>
<DD><A NAME="IDX503"></A>
<A NAME="IDX504"></A>
<A NAME="IDX505"></A>
Add @option{-traditional} to output variable <CODE>CC</CODE> if using the
GNU C compiler and <CODE>ioctl</CODE> does not work properly without
@option{-traditional}. That usually happens when the fixed header files
have not been installed on an old system. Since recent versions of the
GNU C compiler fix the header files automatically when installed,
this is becoming a less prevalent problem.
</DL>
<H3><A NAME="SEC64" HREF="autoconf_toc.html#TOC64">C++ Compiler Characteristics</A></H3>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_CXX</B> <I>(@ovar{compiler-search-list})</I>
<DD><A NAME="IDX506"></A>
<A NAME="IDX507"></A>
<A NAME="IDX508"></A>
<A NAME="IDX509"></A>
Determine a C++ compiler to use. Check if the environment variable
<CODE>CXX</CODE> or <CODE>CCC</CODE> (in that order) is set; if so, then set output
variable <CODE>CXX</CODE> to its value.
<P>
Otherwise, if the macro is invoked without an argument, then search for
a C++ compiler under the likely names (first <CODE>g++</CODE> and <CODE>c++</CODE>
then other names). If none of those checks succeed, then as a last
resort set <CODE>CXX</CODE> to <CODE>g++</CODE>.
<P>
This macro may, however, be invoked with an optional first argument
which, if specified, must be a space separated list of C++ compilers to
search for. This just gives the user an opportunity to specify an
alternative search list for the C++ compiler. For example, if you
didn't like the default order, then you could invoke <CODE>AC_PROG_CXX</CODE>
like this:
<PRE>
AC_PROG_CXX(cl KCC CC cxx cc++ xlC aCC c++ g++ egcs gcc)
</PRE>
<P>
If using the GNU C++ compiler, set shell variable <CODE>GXX</CODE> to
<SAMP>`yes'</SAMP>. If output variable <CODE>CXXFLAGS</CODE> was not already set, set
it to @option{-g -O2} for the GNU C++ compiler (@option{-O2} on
systems where G++ does not accept @option{-g}), or @option{-g} for other
compilers.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_CXXCPP</B>
<DD><A NAME="IDX510"></A>
<A NAME="IDX511"></A>
<A NAME="IDX512"></A>
Set output variable <CODE>CXXCPP</CODE> to a command that runs the C++
preprocessor. If <SAMP>`$CXX -E'</SAMP> doesn't work, <TT>`/lib/cpp'</TT> is used.
It is only portable to run <CODE>CXXCPP</CODE> on files with a <TT>`.c'</TT>,
<TT>`.C'</TT>, or <TT>`.cc'</TT> extension.
<P>
If the current language is C++ (see section <A HREF="autoconf.html#SEC78">Language Choice</A>), many of the
specific test macros use the value of <CODE>CXXCPP</CODE> indirectly by
calling <CODE>AC_TRY_CPP</CODE>, <CODE>AC_CHECK_HEADER</CODE>,
<CODE>AC_EGREP_HEADER</CODE>, or <CODE>AC_EGREP_CPP</CODE>.
<P>
Some preprocessors don't indicate missing include files by the error
status. For such preprocessors an internal variable is set that causes
other macros to check the standard error from the preprocessor and
consider the test failed if any warnings have been reported. However,
it is not known whether such broken preprocessors exist for C++.
</DL>
<H3><A NAME="SEC65" HREF="autoconf_toc.html#TOC65">Fortran 77 Compiler Characteristics</A></H3>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_F77</B> <I>(@ovar{compiler-search-list})</I>
<DD><A NAME="IDX513"></A>
<A NAME="IDX514"></A>
<A NAME="IDX515"></A>
<A NAME="IDX516"></A>
Determine a Fortran 77 compiler to use. If <CODE>F77</CODE> is not already
set in the environment, then check for <CODE>g77</CODE> and <CODE>f77</CODE>, and
then some other names. Set the output variable <CODE>F77</CODE> to the name
of the compiler found.
<P>
This macro may, however, be invoked with an optional first argument
which, if specified, must be a space separated list of Fortran 77
compilers to search for. This just gives the user an opportunity to
specify an alternative search list for the Fortran 77 compiler. For
example, if you didn't like the default order, then you could invoke
<CODE>AC_PROG_F77</CODE> like this:
<PRE>
AC_PROG_F77(fl32 f77 fort77 xlf cf77 g77 f90 xlf90)
</PRE>
<P>
If using <CODE>g77</CODE> (the GNU Fortran 77 compiler), then
<CODE>AC_PROG_F77</CODE> will set the shell variable <CODE>G77</CODE> to <SAMP>`yes'</SAMP>.
If the output variable <CODE>FFLAGS</CODE> was not already set in the
environment, then set it to @option{-g -02} for <CODE>g77</CODE> (or @option{-O2}
where <CODE>g77</CODE> does not accept @option{-g}). Otherwise, set
<CODE>FFLAGS</CODE> to @option{-g} for all other Fortran 77 compilers.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PROG_F77_C_O</B>
<DD><A NAME="IDX517"></A>
<A NAME="IDX518"></A>
<A NAME="IDX519"></A>
Test if the Fortran 77 compiler accepts the options @option{-c} and
@option{-o} simultaneously, and define <CODE>F77_NO_MINUS_C_MINUS_O</CODE> if it
does not.
</DL>
<P>
The following macros check for Fortran 77 compiler characteristics. To
check for characteristics not listed here, use <CODE>AC_TRY_COMPILE</CODE>
(see section <A HREF="autoconf.html#SEC70">Examining Syntax</A>) or <CODE>AC_TRY_RUN</CODE> (see section <A HREF="autoconf.html#SEC72">Checking Run Time Behavior</A>),
making sure to first set the current language to Fortran 77
<CODE>AC_LANG(Fortran 77)</CODE> (see section <A HREF="autoconf.html#SEC78">Language Choice</A>).
<P>
<DL>
<DT><U>Macro:</U> <B>AC_F77_LIBRARY_LDFLAGS</B>
<DD><A NAME="IDX520"></A>
<A NAME="IDX521"></A>
<A NAME="IDX522"></A>
Determine the linker flags (e.g. @option{-L} and @option{-l}) for the
<EM>Fortran 77 intrinsic and run-time libraries</EM> that are required to
successfully link a Fortran 77 program or shared library. The output
variable <CODE>FLIBS</CODE> is set to these flags.
<P>
This macro is intended to be used in those situations when it is
necessary to mix, e.g. C++ and Fortran 77 source code into a single
program or shared library (see section `Mixing Fortran 77 With C and C++' in <CITE>GNU Automake</CITE>).
<P>
For example, if object files from a C++ and Fortran 77 compiler must be
linked together, then the C++ compiler/linker must be used for linking
(since special C++-ish things need to happen at link time like calling
global constructors, instantiating templates, enabling exception
support, etc.).
<P>
However, the Fortran 77 intrinsic and run-time libraries must be linked
in as well, but the C++ compiler/linker doesn't know by default how to
add these Fortran 77 libraries. Hence, the macro
<CODE>AC_F77_LIBRARY_LDFLAGS</CODE> was created to determine these Fortran 77
libraries.
<P>
The macro <CODE>AC_F77_DUMMY_MAIN</CODE> or <CODE>AC_F77_MAIN</CODE> will probably
also be necessary to link C/C++ with Fortran; see below.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_F77_DUMMY_MAIN</B> <I>(@ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX523"></A>
<A NAME="IDX524"></A>
<A NAME="IDX525"></A>
With many compilers, the Fortran libraries detected by
<CODE>AC_F77_LIBRARY_LDFLAGS</CODE> provide their own <CODE>main</CODE> entry
function that initializes things like Fortran I/O, and which then calls
a user-provided entry function named e.g. <CODE>MAIN__</CODE> to run the
user's program. The <CODE>AC_F77_DUMMY_MAIN</CODE> or <CODE>AC_F77_MAIN</CODE>
macro figures out how to deal with this interaction.
<P>
When using Fortran for purely numerical functions (no I/O, etcetera),
users often prefer to provide their own <CODE>main</CODE> and skip the Fortran
library initializations. In this case, however, one may still need to
provide a dummy <CODE>MAIN__</CODE> routine in order to prevent linking errors
on some systems. <CODE>AC_F77_DUMMY_MAIN</CODE> detects whether any such
routine is <EM>required</EM> for linking, and what its name is; the shell
variable <CODE>F77_DUMMY_MAIN</CODE> holds this name, <CODE>unknown</CODE> when no
solution was found, and <CODE>none</CODE> when no such dummy main is needed.
<P>
By default, <VAR>action-if-found</VAR> defines <CODE>F77_DUMMY_MAIN</CODE> to the
name of this routine (e.g. <CODE>MAIN__</CODE>) <EM>if</EM> it is required.
@ovar{action-if-not-found} defaults to exiting with an error.
<P>
In order to link with Fortran routines, the user's C/C++ program should
then include the following code to define the dummy main if it is
needed:
<PRE>
#ifdef F77_DUMMY_MAIN
# ifdef __cplusplus
extern "C"
# endif
int F77_DUMMY_MAIN() { return 1; }
#endif
</PRE>
<P>
Note that <CODE>AC_F77_DUMMY_MAIN</CODE> is called automatically from
<CODE>AC_F77_WRAPPERS</CODE>; there is generally no need to call it explicitly
unless one wants to change the default actions.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_F77_MAIN</B>
<DD><A NAME="IDX526"></A>
<A NAME="IDX527"></A>
<A NAME="IDX528"></A>
As discussed above for <CODE>AC_F77_DUMMY_MAIN</CODE>, many Fortran libraries
allow you to provide an entry point called e.g. <CODE>MAIN__</CODE> instead of
the usual <CODE>main</CODE>, which is then called by a <CODE>main</CODE> function in
the Fortran libraries that initializes things like Fortran I/O. The
<CODE>AC_F77_MAIN</CODE> macro detects whether it is <EM>possible</EM> to
utilize such an alternate main function, and defines <CODE>F77_MAIN</CODE> to
the name of the function. (If no alternate main function name is found,
<CODE>F77_MAIN</CODE> is simply defined to <CODE>main</CODE>.)
<P>
Thus, when calling Fortran routines from C that perform things like I/O,
one should use this macro and name the "main" function <CODE>F77_MAIN</CODE>
instead of <CODE>main</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_F77_WRAPPERS</B>
<DD><A NAME="IDX529"></A>
<A NAME="IDX530"></A>
<A NAME="IDX531"></A>
<A NAME="IDX532"></A>
Defines C macros <CODE>F77_FUNC(name,NAME)</CODE> and
<CODE>F77_FUNC_(name,NAME)</CODE> to properly mangle the names of C/C++
identifiers, and identifiers with underscores, respectively, so that
they match the name-mangling scheme used by the Fortran 77 compiler.
<P>
Fortran 77 is case-insensitive, and in order to achieve this the Fortran
77 compiler converts all identifiers into a canonical case and format.
To call a Fortran 77 subroutine from C or to write a C function that is
callable from Fortran 77, the C program must explicitly use identifiers
in the format expected by the Fortran 77 compiler. In order to do this,
one simply wraps all C identifiers in one of the macros provided by
<CODE>AC_F77_WRAPPERS</CODE>. For example, suppose you have the following
Fortran 77 subroutine:
<PRE>
subroutine foobar(x,y)
double precision x, y
y = 3.14159 * x
return
end
</PRE>
<P>
You would then declare its prototype in C or C++ as:
<PRE>
#define FOOBAR_F77 F77_FUNC(foobar,FOOBAR)
#ifdef __cplusplus
extern "C" /* prevent C++ name mangling */
#endif
void FOOBAR_F77(double *x, double *y);
</PRE>
<P>
Note that we pass both the lowercase and uppercase versions of the
function name to <CODE>F77_FUNC</CODE> so that it can select the right one.
Note also that all parameters to Fortran 77 routines are passed as
pointers (see section `Mixing Fortran 77 With C and C++' in <CITE>GNU Automake</CITE>).
<P>
Although Autoconf tries to be intelligent about detecting the
name-mangling scheme of the Fortran 77 compiler, there may be Fortran 77
compilers that it doesn't support yet. In this case, the above code
will generate a compile-time error, but some other behavior
(e.g. disabling Fortran-related features) can be induced by checking
whether the <CODE>F77_FUNC</CODE> macro is defined.
<P>
Now, to call that routine from a C program, we would do something like:
<PRE>
{
double x = 2.7183, y;
FOOBAR_F77(&x, &y);
}
</PRE>
<P>
If the Fortran 77 identifier contains an underscore
(e.g. <CODE>foo_bar</CODE>), you should use <CODE>F77_FUNC_</CODE> instead of
<CODE>F77_FUNC</CODE> (with the same arguments). This is because some Fortran
77 compilers mangle names differently if they contain an underscore.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_F77_FUNC</B> <I>(<VAR>name</VAR>, @ovar{shellvar})</I>
<DD><A NAME="IDX533"></A>
<A NAME="IDX534"></A>
Given an identifier <VAR>name</VAR>, set the shell variable <VAR>shellvar</VAR> to
hold the mangled version <VAR>name</VAR> according to the rules of the
Fortran 77 linker (see also <CODE>AC_F77_WRAPPERS</CODE>). <VAR>shellvar</VAR> is
optional; if it is not supplied, the shell variable will be simply
<VAR>name</VAR>. The purpose of this macro is to give the caller a way to
access the name-mangling information other than through the C
preprocessor as above; for example, to call Fortran routines from some
language other than C/C++.
</DL>
<H2><A NAME="SEC66" HREF="autoconf_toc.html#TOC66">System Services</A></H2>
<P>
The following macros check for operating system services or capabilities.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PATH_X</B>
<DD><A NAME="IDX535"></A>
<A NAME="IDX536"></A>
Try to locate the X Window System include files and libraries. If the
user gave the command line options @option{--x-includes=<VAR>dir</VAR>} and
@option{--x-libraries=<VAR>dir</VAR>}, use those directories. If either or
both were not given, get the missing values by running <CODE>xmkmf</CODE> on a
trivial <TT>`Imakefile'</TT> and examining the <TT>`Makefile'</TT> that it
produces. If that fails (such as if <CODE>xmkmf</CODE> is not present), look
for them in several directories where they often reside. If either
method is successful, set the shell variables <CODE>x_includes</CODE> and
<CODE>x_libraries</CODE> to their locations, unless they are in directories
the compiler searches by default.
<P>
If both methods fail, or the user gave the command line option
@option{--without-x}, set the shell variable <CODE>no_x</CODE> to <SAMP>`yes'</SAMP>;
otherwise set it to the empty string.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_PATH_XTRA</B>
<DD><A NAME="IDX537"></A>
<A NAME="IDX538"></A>
<A NAME="IDX539"></A>
<A NAME="IDX540"></A>
<A NAME="IDX541"></A>
<A NAME="IDX542"></A>
<A NAME="IDX543"></A>
An enhanced version of <CODE>AC_PATH_X</CODE>. It adds the C compiler flags
that X needs to output variable <CODE>X_CFLAGS</CODE>, and the X linker flags
to <CODE>X_LIBS</CODE>. Define <CODE>X_DISPLAY_MISSING</CODE> if X is not
available.
<P>
This macro also checks for special libraries that some systems need in
order to compile X programs. It adds any that the system needs to
output variable <CODE>X_EXTRA_LIBS</CODE>. And it checks for special X11R6
libraries that need to be linked with before @option{-lX11}, and adds
any found to the output variable <CODE>X_PRE_LIBS</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_SYS_INTERPRETER</B>
<DD><A NAME="IDX544"></A>
<A NAME="IDX545"></A>
Check whether the system supports starting scripts with a line of the
form <SAMP>`#! /bin/csh'</SAMP> to select the interpreter to use for the script.
After running this macro, shell code in @command{configure.ac} can check
the shell variable <CODE>interpval</CODE>; it will be set to <SAMP>`yes'</SAMP>
if the system supports <SAMP>`#!'</SAMP>, <SAMP>`no'</SAMP> if not.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_SYS_LARGEFILE</B>
<DD><A NAME="IDX546"></A>
<A NAME="IDX547"></A>
<A NAME="IDX548"></A>
<A NAME="IDX549"></A>
<A NAME="IDX550"></A>
Arrange for
@href{http://www.sas.com/standards/large.file/x_open.20Mar96.html,
large-file support}. On some hosts, one must use special compiler
options to build programs that can access large files. Append any such
options to the output variable <CODE>CC</CODE>. Define
<CODE>_FILE_OFFSET_BITS</CODE> and <CODE>_LARGE_FILES</CODE> if necessary.
<P>
Large-file support can be disabled by configuring with the
@option{--disable-largefile} option.
<P>
If you use this macro, check that your program works even when
<CODE>off_t</CODE> is longer than <CODE>long</CODE>, since this is common when
large-file support is enabled. For example, it is not correct to print
an arbitrary <CODE>off_t</CODE> value <CODE>X</CODE> with <CODE>printf ("%ld",
(long) X)</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_SYS_LONG_FILE_NAMES</B>
<DD><A NAME="IDX551"></A>
<A NAME="IDX552"></A>
<A NAME="IDX553"></A>
If the system supports file names longer than 14 characters, define
<CODE>HAVE_LONG_FILE_NAMES</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_SYS_POSIX_TERMIOS</B>
<DD><A NAME="IDX554"></A>
<A NAME="IDX555"></A>
<A NAME="IDX556"></A>
<A NAME="IDX557"></A>
Check to see if POSIX termios headers and functions are available on the
system. If so, set the shell variable <CODE>am_cv_sys_posix_termios</CODE> to
<SAMP>`yes'</SAMP>. If not, set the variable to <SAMP>`no'</SAMP>.
</DL>
<H2><A NAME="SEC67" HREF="autoconf_toc.html#TOC67">UNIX Variants</A></H2>
<P>
The following macros check for certain operating systems that need
special treatment for some programs, due to exceptional oddities in
their header files or libraries. These macros are warts; they will be
replaced by a more systematic approach, based on the functions they make
available or the environments they provide.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_AIX</B>
<DD><A NAME="IDX558"></A>
<A NAME="IDX559"></A>
<A NAME="IDX560"></A>
If on AIX, define <CODE>_ALL_SOURCE</CODE>. Allows the use of some BSD
functions. Should be called before any macros that run the C compiler.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_ISC_POSIX</B>
<DD><A NAME="IDX561"></A>
<A NAME="IDX562"></A>
<A NAME="IDX563"></A>
For INTERACTIVE UNIX (ISC), add @option{-lcposix} to output
variable <CODE>LIBS</CODE> if necessary for POSIX facilities. Call this
after <CODE>AC_PROG_CC</CODE> and before any other macros that use POSIX
interfaces. INTERACTIVE UNIX is no longer sold, and Sun says that
they will drop support for it on 2006-07-23, so this macro is becoming
obsolescent.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_MINIX</B>
<DD><A NAME="IDX564"></A>
<A NAME="IDX565"></A>
<A NAME="IDX566"></A>
<A NAME="IDX567"></A>
<A NAME="IDX568"></A>
If on Minix, define <CODE>_MINIX</CODE> and <CODE>_POSIX_SOURCE</CODE> and define
<CODE>_POSIX_1_SOURCE</CODE> to be 2. This allows the use of POSIX
facilities. Should be called before any macros that run the C compiler.
</DL>
<H1><A NAME="SEC68" HREF="autoconf_toc.html#TOC68">Writing Tests</A></H1>
<P>
If the existing feature tests don't do something you need, you have to
write new ones. These macros are the building blocks. They provide
ways for other macros to check whether various kinds of features are
available and report the results.
<P>
This chapter contains some suggestions and some of the reasons why the
existing tests are written the way they are. You can also learn a lot
about how to write Autoconf tests by looking at the existing ones. If
something goes wrong in one or more of the Autoconf tests, this
information can help you understand the assumptions behind them, which
might help you figure out how to best solve the problem.
<P>
These macros check the output of the C compiler system. They do
not cache the results of their tests for future use (see section <A HREF="autoconf.html#SEC82">Caching Results</A>), because they don't know enough about the information they are
checking for to generate a cache variable name. They also do not print
any messages, for the same reason. The checks for particular kinds of C
features call these macros and do cache their results and print messages
about what they're checking for.
<P>
When you write a feature test that could be applicable to more than one
software package, the best thing to do is encapsulate it in a new macro.
See section <A HREF="autoconf.html#SEC101">Writing Autoconf Macros</A>, for how to do that.
<H2><A NAME="SEC69" HREF="autoconf_toc.html#TOC69">Examining Declarations</A></H2>
<P>
The macro <CODE>AC_TRY_CPP</CODE> is used to check whether particular header
files exist. You can check for one at a time, or more than one if you
need several header files to all exist for some purpose.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TRY_CPP</B> <I>(<VAR>input</VAR>, @ovar{action-if-true}, @ovar{action-if-false})</I>
<DD><A NAME="IDX569"></A>
<A NAME="IDX570"></A>
If the preprocessor produces no error messages while processing the
<VAR>input</VAR> (typically includes), run shell commands
<VAR>action-if-true</VAR>. Otherwise run shell commands
<VAR>action-if-false</VAR>. Beware that <VAR>input</VAR> is double quoted. Shell
variable, back quote, and backslash substitutions are performed on
<VAR>input</VAR>.
<P>
This macro uses <CODE>CPPFLAGS</CODE>, but not <CODE>CFLAGS</CODE>, because
@option{-g}, @option{-O}, etc. are not valid options to many C
preprocessors.
</DL>
<P>
Here is how to find out whether a header file contains a particular
declaration, such as a typedef, a structure, a structure member, or a
function. Use <CODE>AC_EGREP_HEADER</CODE> instead of running <CODE>grep</CODE>
directly on the header file; on some systems the symbol might be defined
in another header file that the file you are checking <SAMP>`#include'</SAMP>s.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_EGREP_HEADER</B> <I>(<VAR>pattern</VAR>, <VAR>header-file</VAR>, <VAR>action-if-found</VAR>, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX571"></A>
<A NAME="IDX572"></A>
If the output of running the preprocessor on the system header file
<VAR>header-file</VAR> matches the <CODE>egrep</CODE> regular expression
<VAR>pattern</VAR>, execute shell commands <VAR>action-if-found</VAR>, otherwise
execute <VAR>action-if-not-found</VAR>.
</DL>
<P>
To check for C preprocessor symbols, either defined by header files or
predefined by the C preprocessor, use <CODE>AC_EGREP_CPP</CODE>. Here is an
example of the latter:
<PRE>
AC_EGREP_CPP(yes,
[#ifdef _AIX
yes
#endif
], is_aix=yes, is_aix=no)
</PRE>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_EGREP_CPP</B> <I>(<VAR>pattern</VAR>, <VAR>program</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX573"></A>
<A NAME="IDX574"></A>
<VAR>program</VAR> is the text of a C or C++ program, on which shell
variable, back quote, and backslash substitutions are performed. If the
output of running the preprocessor on <VAR>program</VAR> matches the
<CODE>egrep</CODE> regular expression <VAR>pattern</VAR>, execute shell commands
<VAR>action-if-found</VAR>, otherwise execute <VAR>action-if-not-found</VAR>.
<P>
This macro calls <CODE>AC_PROG_CPP</CODE> or <CODE>AC_PROG_CXXCPP</CODE> (depending
on which language is current, see section <A HREF="autoconf.html#SEC78">Language Choice</A>), if it hasn't
been called already.
</DL>
<H2><A NAME="SEC70" HREF="autoconf_toc.html#TOC70">Examining Syntax</A></H2>
<P>
To check for a syntax feature of the C, C++ or Fortran 77 compiler, such
as whether it recognizes a certain keyword, use <CODE>AC_TRY_COMPILE</CODE> to
try to compile a small program that uses that feature. You can also use
it to check for structures and structure members that are not present on
all systems.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TRY_COMPILE</B> <I>(<VAR>includes</VAR>, <VAR>function-body</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX575"></A>
<A NAME="IDX576"></A>
Create a test program in the current language (see section <A HREF="autoconf.html#SEC78">Language Choice</A>)
to see whether a function whose body consists of <VAR>function-body</VAR> can
be compiled. If the file compiles successfully, run shell commands
<VAR>action-if-found</VAR>, otherwise run <VAR>action-if-not-found</VAR>.
<P>
This macro double quotes both <VAR>includes</VAR> and <VAR>function-body</VAR>.
<P>
For C and C++, <VAR>includes</VAR> is any <CODE>#include</CODE> statements needed
by the code in <VAR>function-body</VAR> (<VAR>includes</VAR> will be ignored if
the currently selected language is Fortran 77). This macro also uses
<CODE>CFLAGS</CODE> or <CODE>CXXFLAGS</CODE> if either C or C++ is the currently
selected language, as well as <CODE>CPPFLAGS</CODE>, when compiling. If
Fortran 77 is the currently selected language then <CODE>FFLAGS</CODE> will be
used when compiling.
<P>
This macro does not try to link; use <CODE>AC_TRY_LINK</CODE> if you need to
do that (see section <A HREF="autoconf.html#SEC71">Examining Libraries</A>).
</DL>
<H2><A NAME="SEC71" HREF="autoconf_toc.html#TOC71">Examining Libraries</A></H2>
<P>
To check for a library, a function, or a global variable, Autoconf
@command{configure} scripts try to compile and link a small program that
uses it. This is unlike Metaconfig, which by default uses <CODE>nm</CODE>
or <CODE>ar</CODE> on the C library to try to figure out which functions are
available. Trying to link with the function is usually a more reliable
approach because it avoids dealing with the variations in the options
and output formats of <CODE>nm</CODE> and <CODE>ar</CODE> and in the location of the
standard libraries. It also allows configuring for cross-compilation or
checking a function's runtime behavior if needed. On the other hand, it
can be slower than scanning the libraries once.
<P>
A few systems have linkers that do not return a failure exit status when
there are unresolved functions in the link. This bug makes the
configuration scripts produced by Autoconf unusable on those systems.
However, some of them can be given options that make the exit status
correct. This is a problem that Autoconf does not currently handle
automatically. If users encounter this problem, they might be able to
solve it by setting <CODE>LDFLAGS</CODE> in the environment to pass whatever
options the linker needs (for example, @option{-Wl,-dn} on @sc{mips
risc/os}).
<P>
<CODE>AC_TRY_LINK</CODE> is used to compile test programs to test for
functions and global variables. It is also used by <CODE>AC_CHECK_LIB</CODE>
to check for libraries (see section <A HREF="autoconf.html#SEC43">Library Files</A>), by adding the library being
checked for to <CODE>LIBS</CODE> temporarily and trying to link a small
program.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TRY_LINK</B> <I>(<VAR>includes</VAR>, <VAR>function-body</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX577"></A>
<A NAME="IDX578"></A>
Depending on the current language (see section <A HREF="autoconf.html#SEC78">Language Choice</A>), create a
test program to see whether a function whose body consists of
<VAR>function-body</VAR> can be compiled and linked. If the file compiles
and links successfully, run shell commands <VAR>action-if-found</VAR>,
otherwise run <VAR>action-if-not-found</VAR>.
<P>
This macro double quotes both <VAR>includes</VAR> and <VAR>function-body</VAR>.
<P>
For C and C++, <VAR>includes</VAR> is any <CODE>#include</CODE> statements needed
by the code in <VAR>function-body</VAR> (<VAR>includes</VAR> will be ignored if
the currently selected language is Fortran 77). This macro also uses
<CODE>CFLAGS</CODE> or <CODE>CXXFLAGS</CODE> if either C or C++ is the currently
selected language, as well as <CODE>CPPFLAGS</CODE>, when compiling. If
Fortran 77 is the currently selected language then <CODE>FFLAGS</CODE> will be
used when compiling. However, both <CODE>LDFLAGS</CODE> and <CODE>LIBS</CODE> will
be used during linking in all cases.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TRY_LINK_FUNC</B> <I>(<VAR>function</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX579"></A>
<A NAME="IDX580"></A>
Depending on the current language (see section <A HREF="autoconf.html#SEC78">Language Choice</A>), create a
test program to see whether a program whose body consists of
a prototype of and a call to <VAR>function</VAR> can be compiled and linked.
<P>
If the file compiles and links successfully, run shell commands
<VAR>action-if-found</VAR>, otherwise run <VAR>action-if-not-found</VAR>.
</DL>
<H2><A NAME="SEC72" HREF="autoconf_toc.html#TOC72">Checking Run Time Behavior</A></H2>
<P>
Sometimes you need to find out how a system performs at run time, such
as whether a given function has a certain capability or bug. If you
can, make such checks when your program runs instead of when it is
configured. You can check for things like the machine's endianness when
your program initializes itself.
<P>
If you really need to test for a run-time behavior while configuring,
you can write a test program to determine the result, and compile and
run it using <CODE>AC_TRY_RUN</CODE>. Avoid running test programs if
possible, because this prevents people from configuring your package for
cross-compiling.
<H3><A NAME="SEC73" HREF="autoconf_toc.html#TOC73">Running Test Programs</A></H3>
<P>
Use the following macro if you need to test run-time behavior of the
system while configuring.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_TRY_RUN</B> <I>(<VAR>program</VAR>, @ovar{action-if-true}, @ovar{action-if-false}, @ovar{action-if-cross-compiling})</I>
<DD><A NAME="IDX581"></A>
<A NAME="IDX582"></A>
If <VAR>program</VAR> compiles and links successfully and returns an exit
status of 0 when executed, run shell commands <VAR>action-if-true</VAR>.
Otherwise, run shell commands <VAR>action-if-false</VAR>.
<P>
This macro double quotes <VAR>program</VAR>, the text of a program in the
current language (see section <A HREF="autoconf.html#SEC78">Language Choice</A>), on which shell variable and
back quote substitutions are performed. This macro uses <CODE>CFLAGS</CODE>
or <CODE>CXXFLAGS</CODE>, <CODE>CPPFLAGS</CODE>, <CODE>LDFLAGS</CODE>, and <CODE>LIBS</CODE>
when compiling.
<P>
If the C compiler being used does not produce executables that run on
the system where @command{configure} is being run, then the test program is
not run. If the optional shell commands <VAR>action-if-cross-compiling</VAR>
are given, they are run instead. Otherwise, @command{configure} prints
an error message and exits.
<P>
In the <VAR>action-if-false</VAR> section, the exit status of the program is
available in the shell variable <SAMP>`$?'</SAMP>, but be very careful to limit
yourself to positive values smaller than 127; bigger values shall be
saved into a file by the <VAR>program</VAR>. Note also that you have simply
no guarantee that this exit status is issued by the <VAR>program</VAR>, or by
the failure of its compilation. In other words, use this feature if
sadist only, it was reestablished because the Autoconf maintainers grew
tired of receiving "bug reports".
</DL>
<P>
Try to provide a pessimistic default value to use when cross-compiling
makes run-time tests impossible. You do this by passing the optional
last argument to <CODE>AC_TRY_RUN</CODE>. @command{autoconf} prints a warning
message when creating @command{configure} each time it encounters a call to
<CODE>AC_TRY_RUN</CODE> with no <VAR>action-if-cross-compiling</VAR> argument
given. You may ignore the warning, though users will not be able to
configure your package for cross-compiling. A few of the macros
distributed with Autoconf produce this warning message.
<P>
To configure for cross-compiling you can also choose a value for those
parameters based on the canonical system name (see section <A HREF="autoconf.html#SEC121">Manual Configuration</A>). Alternatively, set up a test results cache file with
the correct values for the host system (see section <A HREF="autoconf.html#SEC82">Caching Results</A>).
<P>
To provide a default for calls of <CODE>AC_TRY_RUN</CODE> that are embedded in
other macros, including a few of the ones that come with Autoconf, you
can call <CODE>AC_PROG_CC</CODE> before running them. Then, if the shell
variable <CODE>cross_compiling</CODE> is set to <SAMP>`yes'</SAMP>, use an alternate
method to get the results instead of calling the macros.
<H3><A NAME="SEC74" HREF="autoconf_toc.html#TOC74">Guidelines for Test Programs</A></H3>
<P>
Test programs should not write anything to the standard output. They
should return 0 if the test succeeds, nonzero otherwise, so that success
can be distinguished easily from a core dump or other failure;
segmentation violations and other failures produce a nonzero exit
status. Test programs should <CODE>exit</CODE>, not <CODE>return</CODE>, from
<CODE>main</CODE>, because on some systems (old Suns, at least) the argument
to <CODE>return</CODE> in <CODE>main</CODE> is ignored.
<P>
Test programs can use <CODE>#if</CODE> or <CODE>#ifdef</CODE> to check the values of
preprocessor macros defined by tests that have already run. For
example, if you call <CODE>AC_HEADER_STDC</CODE>, then later on in
<TT>`configure.ac'</TT> you can have a test program that includes an
ANSI C header file conditionally:
<PRE>
#if STDC_HEADERS
# include <stdlib.h>
#endif
</PRE>
<P>
If a test program needs to use or create a data file, give it a name
that starts with <TT>`conftest'</TT>, such as <TT>`conftest.data'</TT>. The
@command{configure} script cleans up by running <SAMP>`rm -rf conftest*'</SAMP>
after running test programs and if the script is interrupted.
<H3><A NAME="SEC75" HREF="autoconf_toc.html#TOC75">Test Functions</A></H3>
<P>
Function declarations in test programs should have a prototype
conditionalized for C++. In practice, though, test programs rarely need
functions that take arguments.
<PRE>
#ifdef __cplusplus
foo (int i)
#else
foo (i) int i;
#endif
</PRE>
<P>
Functions that test programs declare should also be conditionalized for
C++, which requires <SAMP>`extern "C"'</SAMP> prototypes. Make sure to not
include any header files containing clashing prototypes.
<PRE>
#ifdef __cplusplus
extern "C" void *malloc (size_t);
#else
char *malloc ();
#endif
</PRE>
<P>
If a test program calls a function with invalid parameters (just to see
whether it exists), organize the program to ensure that it never invokes
that function. You can do this by calling it in another function that is
never invoked. You can't do it by putting it after a call to
<CODE>exit</CODE>, because GCC version 2 knows that <CODE>exit</CODE> never returns
and optimizes out any code that follows it in the same block.
<P>
If you include any header files, make sure to call the functions
relevant to them with the correct number of arguments, even if they are
just 0, to avoid compilation errors due to prototypes. GCC version 2
has internal prototypes for several functions that it automatically
inlines; for example, <CODE>memcpy</CODE>. To avoid errors when checking for
them, either pass them the correct number of arguments or redeclare them
with a different return type (such as <CODE>char</CODE>).
<H2><A NAME="SEC76" HREF="autoconf_toc.html#TOC76">Systemology</A></H2>
<P>
This section aims at presenting some systems and pointers to
documentation. It may help you addressing particular problems reported
by users.
<DL COMPACT>
<DT>QNX 4.25
<DD>
<A NAME="IDX583"></A>
QNX is a realtime operating system running on Intel architecture
meant to be scalable from the small embedded systems to hundred
processor super-computer. It claims to be POSIX certified. More
information is available on the @href{www.qnx.com, QNX home page},
including the @href{http://support.qnx.com/support/docs/qnx4/, QNX
man pages}.
</DL>
<H2><A NAME="SEC77" HREF="autoconf_toc.html#TOC77">Multiple Cases</A></H2>
<P>
Some operations are accomplished in several possible ways, depending on
the UNIX variant. Checking for them essentially requires a "case
statement". Autoconf does not directly provide one; however, it is
easy to simulate by using a shell variable to keep track of whether a
way to perform the operation has been found yet.
<P>
Here is an example that uses the shell variable <CODE>fstype</CODE> to keep
track of whether the remaining cases need to be checked.
<PRE>
AC_MSG_CHECKING([how to get file system type])
fstype=no
# The order of these tests is important.
AC_TRY_CPP([#include <sys/statvfs.h>
#include <sys/fstyp.h>],
[AC_DEFINE(FSTYPE_STATVFS) fstype=SVR4])
if test $fstype = no; then
AC_TRY_CPP([#include <sys/statfs.h>
#include <sys/fstyp.h>],
[AC_DEFINE(FSTYPE_USG_STATFS) fstype=SVR3])
fi
if test $fstype = no; then
AC_TRY_CPP([#include <sys/statfs.h>
#include <sys/vmount.h>],
[AC_DEFINE(FSTYPE_AIX_STATFS) fstype=AIX])
fi
# (more cases omitted here)
AC_MSG_RESULT([$fstype])
</PRE>
<H2><A NAME="SEC78" HREF="autoconf_toc.html#TOC78">Language Choice</A></H2>
<P>
<A NAME="IDX584"></A>
<P>
Autoconf-generated @command{configure} scripts check for the C compiler and
its features by default. Packages that use other programming languages
(maybe more than one, e.g. C and C++) need to test features of the
compilers for the respective languages. The following macros determine
which programming language is used in the subsequent tests in
<TT>`configure.ac'</TT>.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_LANG</B> <I>(<VAR>language</VAR>)</I>
<DD><A NAME="IDX585"></A>
Do compilation tests using the compiler, preprocessor and file
extensions for the specified <VAR>language</VAR>.
<P>
Supported languages are:
<DL COMPACT>
<DT><SAMP>`C'</SAMP>
<DD>
Do compilation tests using <CODE>CC</CODE> and <CODE>CPP</CODE> and use extension
<TT>`.c'</TT> for test programs.
<DT><SAMP>`C++'</SAMP>
<DD>
Do compilation tests using <CODE>CXX</CODE> and <CODE>CXXCPP</CODE> and use
extension <TT>`.C'</TT> for test programs.
<DT><SAMP>`Fortran 77'</SAMP>
<DD>
Do compilation tests using <CODE>F77</CODE> and use extension <TT>`.f'</TT> for
test programs.
</DL>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_LANG_PUSH</B> <I>(<VAR>language</VAR>)</I>
<DD><A NAME="IDX586"></A>
<A NAME="IDX587"></A>
Remember the current language (as set by <CODE>AC_LANG</CODE>) on a stack, and
then select the <VAR>language</VAR>. Use this macro and <CODE>AC_LANG_POP</CODE>
in macros that need to temporarily switch to a particular language.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_LANG_POP</B> <I>(@ovar{language})</I>
<DD><A NAME="IDX588"></A>
<A NAME="IDX589"></A>
Select the language that is saved on the top of the stack, as set by
<CODE>AC_LANG_PUSH</CODE>, and remove it from the stack.
<P>
If given, <VAR>language</VAR> specifies the language we just <EM>quit</EM>. It
is a good idea to specify it when it's known (which should be the
case...), since Autoconf will detect inconsistencies.
<PRE>
AC_LANG_PUSH(Fortran 77)
# Perform some tests on Fortran 77.
# ...
AC_LANG_POP(Fortran 77)
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_REQUIRE_CPP</B>
<DD><A NAME="IDX590"></A>
<A NAME="IDX591"></A>
Ensure that whichever preprocessor would currently be used for tests has
been found. Calls <CODE>AC_REQUIRE</CODE> (see section <A HREF="autoconf.html#SEC106">Prerequisite Macros</A>) with an
argument of either <CODE>AC_PROG_CPP</CODE> or <CODE>AC_PROG_CXXCPP</CODE>,
depending on which language is current.
</DL>
<H1><A NAME="SEC79" HREF="autoconf_toc.html#TOC79">Results of Tests</A></H1>
<P>
Once @command{configure} has determined whether a feature exists, what can
it do to record that information? There are four sorts of things it can
do: define a C preprocessor symbol, set a variable in the output files,
save the result in a cache file for future @command{configure} runs, and
print a message letting the user know the result of the test.
<H2><A NAME="SEC80" HREF="autoconf_toc.html#TOC80">Defining C Preprocessor Symbols</A></H2>
<P>
A common action to take in response to a feature test is to define a C
preprocessor symbol indicating the results of the test. That is done by
calling <CODE>AC_DEFINE</CODE> or <CODE>AC_DEFINE_UNQUOTED</CODE>.
<P>
By default, <CODE>AC_OUTPUT</CODE> places the symbols defined by these macros
into the output variable <CODE>DEFS</CODE>, which contains an option
@option{-D<VAR>symbol</VAR>=<VAR>value</VAR>} for each symbol defined. Unlike in
Autoconf version 1, there is no variable <CODE>DEFS</CODE> defined while
@command{configure} is running. To check whether Autoconf macros have
already defined a certain C preprocessor symbol, test the value of the
appropriate cache variable, as in this example:
<PRE>
AC_CHECK_FUNC(vprintf, [AC_DEFINE(HAVE_VPRINTF)])
if test "$ac_cv_func_vprintf" != yes; then
AC_CHECK_FUNC(_doprnt, [AC_DEFINE(HAVE_DOPRNT)])
fi
</PRE>
<P>
If <CODE>AC_CONFIG_HEADERS</CODE> has been called, then instead of creating
<CODE>DEFS</CODE>, <CODE>AC_OUTPUT</CODE> creates a header file by substituting the
correct values into <CODE>#define</CODE> statements in a template file.
See section <A HREF="autoconf.html#SEC27">Configuration Header Files</A>, for more information about this kind of
output.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_DEFINE</B> <I>(<VAR>variable</VAR>, @ovar{value}, @ovar{description})</I>
<DD><A NAME="IDX592"></A>
<A NAME="IDX593"></A>
Define C preprocessor variable <VAR>variable</VAR>. If <VAR>value</VAR> is given,
set <VAR>variable</VAR> to that value (verbatim), otherwise set it to 1.
<VAR>value</VAR> should not contain literal newlines, and if you are not
using <CODE>AC_CONFIG_HEADERS</CODE> it should not contain any <SAMP>`#'</SAMP>
characters, as <CODE>make</CODE> tends to eat them. To use a shell variable
(which you need to do in order to define a value containing the M4 quote
characters <SAMP>`['</SAMP> or <SAMP>`]'</SAMP>), use <CODE>AC_DEFINE_UNQUOTED</CODE> instead.
<VAR>description</VAR> is only useful if you are using
<CODE>AC_CONFIG_HEADERS</CODE>. In this case, <VAR>description</VAR> is put into
the generated <TT>`config.h.in'</TT> as the comment before the macro define.
The following example defines the C preprocessor variable
<CODE>EQUATION</CODE> to be the string constant <SAMP>`"$a > $b"'</SAMP>:
<PRE>
AC_DEFINE(EQUATION, "$a > $b")
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_DEFINE_UNQUOTED</B> <I>(<VAR>variable</VAR>, @ovar{value}, @ovar{description})</I>
<DD><A NAME="IDX594"></A>
<A NAME="IDX595"></A>
Like <CODE>AC_DEFINE</CODE>, but three shell expansions are
performed--once--on <VAR>variable</VAR> and <VAR>value</VAR>: variable expansion
(<SAMP>`$'</SAMP>), command substitution (<SAMP>``'</SAMP>), and backslash escaping
(<SAMP>`\'</SAMP>). Single and double quote characters in the value have no
special meaning. Use this macro instead of <CODE>AC_DEFINE</CODE> when
<VAR>variable</VAR> or <VAR>value</VAR> is a shell variable. Examples:
<PRE>
AC_DEFINE_UNQUOTED(config_machfile, "$machfile")
AC_DEFINE_UNQUOTED(GETGROUPS_T, $ac_cv_type_getgroups)
AC_DEFINE_UNQUOTED($ac_tr_hdr)
</PRE>
</DL>
<P>
Due to the syntactical bizarreness of the Bourne shell, do not use
semicolons to separate <CODE>AC_DEFINE</CODE> or <CODE>AC_DEFINE_UNQUOTED</CODE>
calls from other macro calls or shell code; that can cause syntax errors
in the resulting @command{configure} script. Use either spaces or
newlines. That is, do this:
<PRE>
AC_CHECK_HEADER(elf.h, [AC_DEFINE(SVR4) LIBS="$LIBS -lelf"])
</PRE>
<P>
or this:
<PRE>
AC_CHECK_HEADER(elf.h,
[AC_DEFINE(SVR4)
LIBS="$LIBS -lelf"])
</PRE>
<P>
instead of this:
<PRE>
AC_CHECK_HEADER(elf.h, [AC_DEFINE(SVR4); LIBS="$LIBS -lelf"])
</PRE>
<H2><A NAME="SEC81" HREF="autoconf_toc.html#TOC81">Setting Output Variables</A></H2>
<P>
Another way to record the results of tests is to set <EM>output
variables</EM>, which are shell variables whose values are substituted into
files that @command{configure} outputs. The two macros below create new
output variables. See section <A HREF="autoconf.html#SEC23">Preset Output Variables</A>, for a list of output
variables that are always available.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_SUBST</B> <I>(<VAR>variable</VAR>, @ovar{value})</I>
<DD><A NAME="IDX596"></A>
<A NAME="IDX597"></A>
Create an output variable from a shell variable. Make <CODE>AC_OUTPUT</CODE>
substitute the variable <VAR>variable</VAR> into output files (typically one
or more <TT>`Makefile'</TT>s). This means that <CODE>AC_OUTPUT</CODE> will
replace instances of <SAMP>`@<VAR>variable</VAR>@'</SAMP> in input files with the
value that the shell variable <VAR>variable</VAR> has when <CODE>AC_OUTPUT</CODE>
is called. This value of <VAR>variable</VAR> should not contain literal
newlines.
<P>
If <VAR>value</VAR> is given, in addition assign it to <SAMP>`variable'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_SUBST_FILE</B> <I>(<VAR>variable</VAR>)</I>
<DD><A NAME="IDX598"></A>
<A NAME="IDX599"></A>
Another way to create an output variable from a shell variable. Make
<CODE>AC_OUTPUT</CODE> insert (without substitutions) the contents of the file
named by shell variable <VAR>variable</VAR> into output files. This means
that <CODE>AC_OUTPUT</CODE> will replace instances of
<SAMP>`@<VAR>variable</VAR>@'</SAMP> in output files (such as <TT>`Makefile.in'</TT>)
with the contents of the file that the shell variable <VAR>variable</VAR>
names when <CODE>AC_OUTPUT</CODE> is called. Set the variable to
<TT>`/dev/null'</TT> for cases that do not have a file to insert.
<P>
This macro is useful for inserting <TT>`Makefile'</TT> fragments containing
special dependencies or other <CODE>make</CODE> directives for particular host
or target types into <TT>`Makefile'</TT>s. For example, <TT>`configure.ac'</TT>
could contain:
<PRE>
AC_SUBST_FILE(host_frag)
host_frag=$srcdir/conf/sun4.mh
</PRE>
<P>
and then a <TT>`Makefile.in'</TT> could contain:
<PRE>
@host_frag@
</PRE>
</DL>
<P>
<A NAME="IDX600"></A>
<A NAME="IDX601"></A>
Running @command{configure} in different environments can be extremely
dangerous. If for instance the user runs <SAMP>`CC=bizarre-cc
./configure'</SAMP>, then the cache, <TT>`config.h'</TT> and many other output
files will depend upon @command{bizarre-cc} being the C compiler. If
for some reason the user runs @command{/configure} again, or if it is
run via <SAMP>`./config.status --recheck'</SAMP>, (See section <A HREF="autoconf.html#SEC26">Automatic Remaking</A>,
and see section <A HREF="autoconf.html#SEC145">Recreating a Configuration</A>), then the configuration can be
inconsistent, composed of results depending upon two different
compilers.
<P>
Such variables are named <EM>precious variables</EM>, and can be declared
as such by <CODE>AC_ARG_VAR</CODE>.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_ARG_VAR</B> <I>(<VAR>variable</VAR>, <VAR>description</VAR>)</I>
<DD><A NAME="IDX602"></A>
<A NAME="IDX603"></A>
Declare <VAR>variable</VAR> is a precious variable, and include its
<VAR>description</VAR> in the variable section of <SAMP>`./configure --help'</SAMP>.
<P>
Being precious means that
<UL>
<LI>
<VAR>variable</VAR> is <CODE>AC_SUBST</CODE>'d.
<LI>
<VAR>variable</VAR> is kept in the cache including if it was not specified on
the <SAMP>`./configure'</SAMP> command line. Indeed, while @command{configure}
can notice the definition of <CODE>CC</CODE> in <SAMP>`./configure
CC=bizarre-cc'</SAMP>, it is impossible to notice it in <SAMP>`CC=bizarre-cc
./configure'</SAMP>, which, unfortunately, is what most users do.
<LI>
<VAR>variable</VAR> is checked for consistency between two
@command{configure} runs. For instance:
<PRE>
$ <KBD>./configure --silent --config-cache</KBD>
$ <KBD>CC=cc ./configure --silent --config-cache</KBD>
configure: error: `CC' was not set in the previous run
configure: error: changes in the environment can compromise \
the build
configure: error: run `make distclean' and/or \
`rm config.cache' and start over
</PRE>
and similarly if the variable is unset, or if its content is changed.
<LI>
<VAR>variable</VAR> is kept during automatic reconfiguration
(see section <A HREF="autoconf.html#SEC145">Recreating a Configuration</A>) as if it had been passed as a command
line argument, including when no cache is used:
<PRE>
$ <KBD>CC=/usr/bin/cc ./configure undeclared_var=raboof --silent</KBD>
$ <KBD>./config.status --recheck</KBD>
running /bin/sh ./configure undeclared_var=raboof --silent \
CC=/usr/bin/cc --no-create --no-recursion
</PRE>
</UL>
</DL>
<H2><A NAME="SEC82" HREF="autoconf_toc.html#TOC82">Caching Results</A></H2>
<P>
<A NAME="IDX604"></A>
<P>
To avoid checking for the same features repeatedly in various
@command{configure} scripts (or in repeated runs of one script),
@command{configure} can optionally save the results of many checks in a
<EM>cache file</EM> (see section <A HREF="autoconf.html#SEC84">Cache Files</A>). If a @command{configure} script
runs with caching enabled and finds a cache file, it reads the results
of previous runs from the cache and avoids rerunning those checks. As a
result, @command{configure} can then run much faster than if it had to
perform all of the checks every time.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CACHE_VAL</B> <I>(<VAR>cache-id</VAR>, <VAR>commands-to-set-it</VAR>)</I>
<DD><A NAME="IDX605"></A>
<A NAME="IDX606"></A>
Ensure that the results of the check identified by <VAR>cache-id</VAR> are
available. If the results of the check were in the cache file that was
read, and @command{configure} was not given the @option{--quiet} or
@option{--silent} option, print a message saying that the result was
cached; otherwise, run the shell commands <VAR>commands-to-set-it</VAR>. If
the shell commands are run to determine the value, the value will be
saved in the cache file just before @command{configure} creates its output
files. See section <A HREF="autoconf.html#SEC83">Cache Variable Names</A>, for how to choose the name of the
<VAR>cache-id</VAR> variable.
<P>
The <VAR>commands-to-set-it</VAR> <EM>must have no side effects</EM> except for
setting the variable <VAR>cache-id</VAR>, see below.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CACHE_CHECK</B> <I>(<VAR>message</VAR>, <VAR>cache-id</VAR>, <VAR>commands-to-set-it</VAR>)</I>
<DD><A NAME="IDX607"></A>
<A NAME="IDX608"></A>
A wrapper for <CODE>AC_CACHE_VAL</CODE> that takes care of printing the
messages. This macro provides a convenient shorthand for the most
common way to use these macros. It calls <CODE>AC_MSG_CHECKING</CODE> for
<VAR>message</VAR>, then <CODE>AC_CACHE_VAL</CODE> with the <VAR>cache-id</VAR> and
<VAR>commands</VAR> arguments, and <CODE>AC_MSG_RESULT</CODE> with <VAR>cache-id</VAR>.
<P>
The <VAR>commands-to-set-it</VAR> <EM>must have no side effects</EM> except for
setting the variable <VAR>cache-id</VAR>, see below.
</DL>
<P>
It is very common to find buggy macros using <CODE>AC_CACHE_VAL</CODE> or
<CODE>AC_CACHE_CHECK</CODE>, because people are tempted to call
<CODE>AC_DEFINE</CODE> in the <VAR>commands-to-set-it</VAR>. Instead, the code that
<EM>follows</EM> the call to <CODE>AC_CACHE_VAL</CODE> should call
<CODE>AC_DEFINE</CODE>, by examining the value of the cache variable. For
instance, the following macro is broken:
<PRE>
AC_DEFUN([AC_SHELL_TRUE],
[AC_CACHE_CHECK([whether true(1) works], [ac_cv_shell_true_works],
[ac_cv_shell_true_works=no
true && ac_cv_shell_true_works=yes
if test $ac_cv_shell_true_works = yes; then
AC_DEFINE([TRUE_WORKS], 1
[Define if `true(1)' works properly.])
fi])
])
</PRE>
<P>
This fails if the cache is enabled: the second time this macro is run,
<CODE>TRUE_WORKS</CODE> <EM>will not be defined</EM>. The proper implementation
is:
<PRE>
AC_DEFUN([AC_SHELL_TRUE],
[AC_CACHE_CHECK([whether true(1) works], [ac_cv_shell_true_works],
[ac_cv_shell_true_works=no
true && ac_cv_shell_true_works=yes])
if test $ac_cv_shell_true_works = yes; then
AC_DEFINE([TRUE_WORKS], 1
[Define if `true(1)' works properly.])
fi
])
</PRE>
<P>
Also, <VAR>commands-to-set-it</VAR> should not print any messages, for
example with <CODE>AC_MSG_CHECKING</CODE>; do that before calling
<CODE>AC_CACHE_VAL</CODE>, so the messages are printed regardless of whether
the results of the check are retrieved from the cache or determined by
running the shell commands.
<H3><A NAME="SEC83" HREF="autoconf_toc.html#TOC83">Cache Variable Names</A></H3>
<P>
<A NAME="IDX609"></A>
<P>
The names of cache variables should have the following format:
<PRE>
<VAR>package-prefix</VAR>_cv_<VAR>value-type</VAR>_<VAR>specific-value</VAR>_@ovar{additional-options}
</PRE>
<P>
for example, <SAMP>`ac_cv_header_stat_broken'</SAMP> or
<SAMP>`ac_cv_prog_gcc_traditional'</SAMP>. The parts of the variable name are:
<DL COMPACT>
<DT><VAR>package-prefix</VAR>
<DD>
An abbreviation for your package or organization; the same prefix you
begin local Autoconf macros with, except lowercase by convention.
For cache values used by the distributed Autoconf macros, this value is
<SAMP>`ac'</SAMP>.
<DT><CODE>_cv_</CODE>
<DD>
Indicates that this shell variable is a cache value. This string
<EM>must</EM> be present in the variable name, including the leading
underscore.
<DT><VAR>value-type</VAR>
<DD>
A convention for classifying cache values, to produce a rational naming
system. The values used in Autoconf are listed in section <A HREF="autoconf.html#SEC103">Macro Names</A>.
<DT><VAR>specific-value</VAR>
<DD>
Which member of the class of cache values this test applies to.
For example, which function (<SAMP>`alloca'</SAMP>), program (<SAMP>`gcc'</SAMP>), or
output variable (<SAMP>`INSTALL'</SAMP>).
<DT><VAR>additional-options</VAR>
<DD>
Any particular behavior of the specific member that this test applies to.
For example, <SAMP>`broken'</SAMP> or <SAMP>`set'</SAMP>. This part of the name may
be omitted if it does not apply.
</DL>
<P>
The values assigned to cache variables may not contain newlines.
Usually, their values will be boolean (<SAMP>`yes'</SAMP> or <SAMP>`no'</SAMP>) or the
names of files or functions; so this is not an important restriction.
<H3><A NAME="SEC84" HREF="autoconf_toc.html#TOC84">Cache Files</A></H3>
<P>
A cache file is a shell script that caches the results of configure
tests run on one system so they can be shared between configure scripts
and configure runs. It is not useful on other systems. If its contents
are invalid for some reason, the user may delete or edit it.
<P>
By default, @command{configure} uses no cache file (technically, it uses
@option{--cache-file=/dev/null}), to avoid problems caused by accidental
use of stale cache files.
<P>
To enable caching, @command{configure} accepts @option{--config-cache} (or
@option{-C}) to cache results in the file <TT>`config.cache'</TT>.
Alternatively, @option{--cache-file=<VAR>file</VAR>} specifies that
<VAR>file</VAR> be the cache file. The cache file is created if it does not
exist already. When @command{configure} calls @command{configure} scripts in
subdirectories, it uses the @option{--cache-file} argument so that they
share the same cache. See section <A HREF="autoconf.html#SEC33">Configuring Other Packages in Subdirectories</A>, for information on
configuring subdirectories with the <CODE>AC_CONFIG_SUBDIRS</CODE> macro.
<P>
<TT>`config.status'</TT> only pays attention to the cache file if it is
given the @option{--recheck} option, which makes it rerun
@command{configure}.
<P>
It is wrong to try to distribute cache files for particular system types.
There is too much room for error in doing that, and too much
administrative overhead in maintaining them. For any features that
can't be guessed automatically, use the standard method of the canonical
system type and linking files (see section <A HREF="autoconf.html#SEC121">Manual Configuration</A>).
<P>
The site initialization script can specify a site-wide cache file to
use, instead of the usual per-program cache. In this case, the cache
file will gradually accumulate information whenever someone runs a new
@command{configure} script. (Running @command{configure} merges the new cache
results with the existing cache file.) This may cause problems,
however, if the system configuration (e.g. the installed libraries or
compilers) changes and the stale cache file is not deleted.
<H3><A NAME="SEC85" HREF="autoconf_toc.html#TOC85">Cache Checkpointing</A></H3>
<P>
If your configure script, or a macro called from configure.ac, happens
to abort the configure process, it may be useful to checkpoint the cache
a few times at key points using <CODE>AC_CACHE_SAVE</CODE>. Doing so will
reduce the amount of time it takes to re-run the configure script with
(hopefully) the error that caused the previous abort corrected.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CACHE_LOAD</B>
<DD><A NAME="IDX610"></A>
<A NAME="IDX611"></A>
Loads values from existing cache file, or creates a new cache file if a
cache file is not found. Called automatically from <CODE>AC_INIT</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CACHE_SAVE</B>
<DD><A NAME="IDX612"></A>
<A NAME="IDX613"></A>
Flushes all cached values to the cache file. Called automatically from
<CODE>AC_OUTPUT</CODE>, but it can be quite useful to call
<CODE>AC_CACHE_SAVE</CODE> at key points in configure.ac.
</DL>
<P>
For instance:
<PRE>
... AC_INIT, etc. ...
# Checks for programs.
AC_PROG_CC
AC_PROG_GCC_TRADITIONAL
... more program checks ...
AC_CACHE_SAVE
# Checks for libraries.
AC_CHECK_LIB(nsl, gethostbyname)
AC_CHECK_LIB(socket, connect)
... more lib checks ...
AC_CACHE_SAVE
# Might abort...
AM_PATH_GTK(1.0.2,, [AC_MSG_ERROR([GTK not in path])])
AM_PATH_GTKMM(0.9.5,, [AC_MSG_ERROR([GTK not in path])])
... AC_OUTPUT, etc. ...
</PRE>
<H2><A NAME="SEC86" HREF="autoconf_toc.html#TOC86">Printing Messages</A></H2>
<P>
<A NAME="IDX614"></A>
<P>
@command{configure} scripts need to give users running them several kinds
of information. The following macros print messages in ways appropriate
for each kind. The arguments to all of them get enclosed in shell
double quotes, so the shell performs variable and back-quote
substitution on them.
<P>
These macros are all wrappers around the <CODE>echo</CODE> shell command.
@command{configure} scripts should rarely need to run <CODE>echo</CODE> directly
to print messages for the user. Using these macros makes it easy to
change how and when each kind of message is printed; such changes need
only be made to the macro definitions and all of the callers will change
automatically.
<P>
To diagnose static issues, i.e., when @command{autoconf} is run, see
section <A HREF="autoconf.html#SEC104">Reporting Messages</A>.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_MSG_CHECKING</B> <I>(<VAR>feature-description</VAR>)</I>
<DD><A NAME="IDX615"></A>
<A NAME="IDX616"></A>
Notify the user that @command{configure} is checking for a particular
feature. This macro prints a message that starts with <SAMP>`checking '</SAMP>
and ends with <SAMP>`...'</SAMP> and no newline. It must be followed by a call
to <CODE>AC_MSG_RESULT</CODE> to print the result of the check and the
newline. The <VAR>feature-description</VAR> should be something like
<SAMP>`whether the Fortran compiler accepts C++ comments'</SAMP> or <SAMP>`for
c89'</SAMP>.
<P>
This macro prints nothing if @command{configure} is run with the
@option{--quiet} or @option{--silent} option.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_MSG_RESULT</B> <I>(<VAR>result-description</VAR>)</I>
<DD><A NAME="IDX617"></A>
<A NAME="IDX618"></A>
Notify the user of the results of a check. <VAR>result-description</VAR> is
almost always the value of the cache variable for the check, typically
<SAMP>`yes'</SAMP>, <SAMP>`no'</SAMP>, or a file name. This macro should follow a call
to <CODE>AC_MSG_CHECKING</CODE>, and the <VAR>result-description</VAR> should be
the completion of the message printed by the call to
<CODE>AC_MSG_CHECKING</CODE>.
<P>
This macro prints nothing if @command{configure} is run with the
@option{--quiet} or @option{--silent} option.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_MSG_NOTICE</B> <I>(<VAR>message</VAR>)</I>
<DD><A NAME="IDX619"></A>
<A NAME="IDX620"></A>
Deliver the <VAR>message</VAR> to the user. It is useful mainly to print a
general description of the overall purpose of a group of feature checks,
e.g.,
<PRE>
AC_MSG_NOTICE([checking if stack overflow is detectable])
</PRE>
<P>
This macro prints nothing if @command{configure} is run with the
@option{--quiet} or @option{--silent} option.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_MSG_ERROR</B> <I>(<VAR>error-description</VAR>, @ovar{exit-status})</I>
<DD><A NAME="IDX621"></A>
<A NAME="IDX622"></A>
Notify the user of an error that prevents @command{configure} from
completing. This macro prints an error message to the standard error
output and exits @command{configure} with <VAR>exit-status</VAR> (1 by default).
<VAR>error-description</VAR> should be something like <SAMP>`invalid value
$HOME for \$HOME'</SAMP>.
<P>
The <VAR>error-description</VAR> should start with a lower-case letter, and
"cannot" is preferred to "can't".
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_MSG_WARN</B> <I>(<VAR>problem-description</VAR>)</I>
<DD><A NAME="IDX623"></A>
<A NAME="IDX624"></A>
Notify the @command{configure} user of a possible problem. This macro
prints the message to the standard error output; @command{configure}
continues running afterward, so macros that call <CODE>AC_MSG_WARN</CODE> should
provide a default (back-up) behavior for the situations they warn about.
<VAR>problem-description</VAR> should be something like <SAMP>`ln -s seems to
make hard links'</SAMP>.
</DL>
<H1><A NAME="SEC87" HREF="autoconf_toc.html#TOC87">Programming in M4</A></H1>
<P>
Autoconf is written on top of two layers: <EM>M4sugar</EM>, which provides
convenient macros for pure M4 programming, and <EM>M4sh</EM>, which
provides macros dedicated to shell script generation.
<P>
As of this version of Autoconf, these two layers are still experimental,
and their interface might change in the future. As a matter of fact,
<EM>anything that is not documented must not be used</EM>.
<H2><A NAME="SEC88" HREF="autoconf_toc.html#TOC88">M4 Quotation</A></H2>
<P>
<A NAME="IDX625"></A>
<P>
The most common brokenness of existing macros is an improper quotation.
This section, which users of Autoconf can skip, but which macro writers
<EM>must</EM> read, first justifies the quotation scheme that was chosen
for Autoconf and then ends with a rule of thumb. Understanding the
former helps one to follow the latter.
<H3><A NAME="SEC89" HREF="autoconf_toc.html#TOC89">Active Characters</A></H3>
<P>
To fully understand where proper quotation is important, you first need
to know what are the special characters in Autoconf: <SAMP>`#'</SAMP> introduces
a comment inside which no macro expansion is performed, <SAMP>`,'</SAMP>
separates arguments, <SAMP>`['</SAMP> and <SAMP>`]'</SAMP> are the quotes themselves,
and finally <SAMP>`('</SAMP> and <SAMP>`)'</SAMP> (which <CODE>m4</CODE> tries to match by
pairs).
<P>
In order to understand the delicate case of macro calls, we first have
to present some obvious failures. Below they are "obvious-ified",
although you find them in real life, they are usually in disguise.
<P>
Comments, introduced by a hash and running up to the newline, are opaque
tokens to the top level: active characters are turned off, and there is
no macro expansion:
<PRE>
# define([def], ine)
=># define([def], ine)
</PRE>
<P>
Each time there can be a macro expansion, there is a quotation
expansion; i.e., one level of quotes is stripped:
<PRE>
int tab[10];
=>int tab10;
[int tab[10];]
=>int tab[10];
</PRE>
<P>
Without this in mind, the reader will try hopelessly to use her macro
<CODE>array</CODE>:
<PRE>
define([array], [int tab[10];])
array
=>int tab10;
[array]
=>array
</PRE>
<P>
How can you correctly output the intended results<A NAME="DOCF2" HREF="autoconf_foot.html#FOOT2">(2)</A>?
<H3><A NAME="SEC90" HREF="autoconf_toc.html#TOC90">One Macro Call</A></H3>
<P>
Let's proceed on the interaction between active characters and macros
with this small macro, which just returns its first argument:
<PRE>
define([car], [$1])
</PRE>
<P>
The two pairs of quotes above are not part of the arguments of
<CODE>define</CODE>; rather, they are understood by the top level when it
tries to find the arguments of <CODE>define</CODE>. Therefore, it is
equivalent to write:
<PRE>
define(car, $1)
</PRE>
<P>
But, while it is acceptable for a <TT>`configure.ac'</TT> to avoid unneeded
quotes, it is bad practice for Autoconf macros which must both be more
robust and also advocate perfect style.
<P>
At the top level, there are only two possible quotings: either you
quote or you don't:
<PRE>
car(foo, bar, baz)
=>foo
[car(foo, bar, baz)]
=>car(foo, bar, baz)
</PRE>
<P>
Let's pay attention to the special characters:
<PRE>
car(#)
error-->EOF in argument list
</PRE>
<P>
The closing parenthesis is hidden in the comment; with a hypothetical
quoting, the top level understood it this way:
<PRE>
car([#)]
</PRE>
<P>
Proper quotation, of course, fixes the problem:
<PRE>
car([#])
=>#
</PRE>
<P>
The reader will easily understand the following examples:
<PRE>
car(foo, bar)
=>foo
car([foo, bar])
=>foo, bar
car((foo, bar))
=>(foo, bar)
car([(foo], [bar)])
=>(foo
car([], [])
=>
car([[]], [[]])
=>[]
</PRE>
<P>
With this in mind, we can explore the cases where macros invoke
macros...
<H3><A NAME="SEC91" HREF="autoconf_toc.html#TOC91">Quotation and Nested Macros</A></H3>
<P>
The examples below use the following macros:
<PRE>
define([car], [$1])
define([active], [ACT, IVE])
define([array], [int tab[10]])
</PRE>
<P>
Each additional embedded macro call introduces other possible
interesting quotations:
<PRE>
car(active)
=>ACT
car([active])
=>ACT, IVE
car([[active]])
=>active
</PRE>
<P>
In the first case, the top level looks for the arguments of <CODE>car</CODE>,
and finds <SAMP>`active'</SAMP>. Because <CODE>m4</CODE> evaluates its arguments
before applying the macro, <SAMP>`active'</SAMP> is expanded, which results in:
<PRE>
car(ACT, IVE)
=>ACT
</PRE>
<P>
In the second case, the top level gives <SAMP>`active'</SAMP> as first and only
argument of <CODE>car</CODE>, which results in:
<PRE>
active
=>ACT, IVE
</PRE>
<P>
i.e., the argument is evaluated <EM>after</EM> the macro that invokes it.
In the third case, <CODE>car</CODE> receives <SAMP>`[active]'</SAMP>, which results in:
<PRE>
[active]
=>active
</PRE>
<P>
exactly as we already saw above.
<P>
The example above, applied to a more realistic example, gives:
<PRE>
car(int tab[10];)
=>int tab10;
car([int tab[10];])
=>int tab10;
car([[int tab[10];]])
=>int tab[10];
</PRE>
<P>
Huh? The first case is easily understood, but why is the second wrong,
and the third right? To understand that, you must know that after
<CODE>m4</CODE> expands a macro, the resulting text is immediately subjected
to macro expansion and quote removal. This means that the quote removal
occurs twice--first before the argument is passed to the <CODE>car</CODE>
macro, and second after the <CODE>car</CODE> macro expands to the first
argument.
<P>
As the author of the Autoconf macro <CODE>car</CODE>, you then consider it to
be incorrect that your users have to double-quote the arguments of
<CODE>car</CODE>, so you "fix" your macro. Let's call it <CODE>qar</CODE> for
quoted car:
<PRE>
define([qar], [[$1]])
</PRE>
<P>
and check that <CODE>qar</CODE> is properly fixed:
<PRE>
qar([int tab[10];])
=>int tab[10];
</PRE>
<P>
Ahhh! That's much better.
<P>
But note what you've done: now that the arguments are literal strings,
if the user wants to use the results of expansions as arguments, she has
to use an <EM>unquoted</EM> macro call:
<PRE>
qar(active)
=>ACT
</PRE>
<P>
where she wanted to reproduce what she used to do with <CODE>car</CODE>:
<PRE>
car([active])
=>ACT, IVE
</PRE>
<P>
Worse yet: she wants to use a macro that produces a set of <CODE>cpp</CODE>
macros:
<PRE>
define([my_includes], [#include <stdio.h>])
car([my_includes])
=>#include <stdio.h>
qar(my_includes)
error-->EOF in argument list
</PRE>
<P>
This macro, <CODE>qar</CODE>, because it double quotes its arguments, forces
its users to leave their macro calls unquoted, which is dangerous.
Commas and other active symbols are interpreted by <CODE>m4</CODE> before
they are given to the macro, often not in the way the users expect.
Also, because <CODE>qar</CODE> behaves differently from the other macros,
it's an exception that should be avoided in Autoconf.
<H3><A NAME="SEC92" HREF="autoconf_toc.html#TOC92"><CODE>changequote</CODE> is Evil</A></H3>
<P>
The temptation is often high to bypass proper quotation, in particular
when it's late at night. Then, many experienced Autoconf hackers
finally surrender to the dark side of the force and use the ultimate
weapon: <CODE>changequote</CODE>.
<P>
The M4 builtin <CODE>changequote</CODE> belongs to a set of primitives that
allow one to adjust the syntax of the language to adjust it to her
needs. For instance, by default M4 uses <SAMP>``'</SAMP> and <SAMP>`''</SAMP> as
quotes, but in the context of shell programming (and actually of most
programming languages), it's about the worst choice one can make:
because of strings and back quoted expression in shell (such as
<SAMP>`'this''</SAMP> and <SAMP>``that`'</SAMP>), because of literal characters in usual
programming language (as in <SAMP>`'0''</SAMP>), there are many unbalanced
<SAMP>``'</SAMP> and <SAMP>`''</SAMP>. Proper M4 quotation then becomes a nightmare, if
not impossible. In order to make M4 useful in such a context, its
designers have equipped it with <CODE>changequote</CODE>, which makes it
possible to chose another pair of quotes. M4sugar, M4sh, Autoconf, and
Autotest all have chosen to use <SAMP>`['</SAMP> and <SAMP>`]'</SAMP>. Not especially
because they are unlikely characters, but <EM>because they are
characters unlikely to be unbalanced</EM>.
<P>
There are other magic primitives, such as <CODE>changecom</CODE> to specify
what syntactic forms are comments (it is common to see
<SAMP>`changecom(<!--, -->)'</SAMP> when M4 is used to produce HTML pages),
<CODE>changeword</CODE> and <CODE>changesyntax</CODE> to change other syntactic
details (such as the character to denote the n-th argument, <SAMP>`$'</SAMP> by
default, the parenthesis around arguments etc.).
<P>
These primitives are really meant to make M4 more useful for specific
domains: they should be considered like command line options:
@option{--quotes}, @option{--comments}, @option{--words}, and
<CODE>--syntax</CODE>. Nevertheless, they are implemented as M4 builtins, as
it makes M4 libraries self contained (no need for additional options).
<P>
There lies the problem...
<P>
The problem is that it is then tempting to use them in the middle of an
M4 script, as opposed to its initialization. This, if not carefully
thought, can lead to disastrous effects: <EM>you are changing the
language in the middle of the execution</EM>. Changing and restoring the
syntax is often not enough: if you happened to invoke macros in between,
these macros will be lost, as the current syntax will probably not be
the one they were implemented with.
<H3><A NAME="SEC93" HREF="autoconf_toc.html#TOC93">Quadrigraphs</A></H3>
<P>
<A NAME="IDX626"></A>
<A NAME="IDX627"></A>
<A NAME="IDX628"></A>
<A NAME="IDX629"></A>
<A NAME="IDX630"></A>
<A NAME="IDX631"></A>
<P>
When writing an autoconf macro you may occasionally need to generate
special characters that are difficult to express with the standard
autoconf quoting rules. For example, you may need to output the regular
expression <SAMP>`[^[]'</SAMP>, which matches any character other than <SAMP>`['</SAMP>.
This expression contains unbalanced brackets so it cannot be put easily
into an M4 macro.
<P>
You can work around this problem by using one of the following
<EM>quadrigraphs</EM>:
<DL COMPACT>
<DT><SAMP>`@<:@'</SAMP>
<DD>
<SAMP>`['</SAMP>
<DT><SAMP>`@:>@'</SAMP>
<DD>
<SAMP>`]'</SAMP>
<DT><SAMP>`@S|@'</SAMP>
<DD>
<SAMP>`$'</SAMP>
<DT><SAMP>`@%:@'</SAMP>
<DD>
<SAMP>`#'</SAMP>
<DT><SAMP>`@&t@'</SAMP>
<DD>
Expands to nothing.
</DL>
<P>
Quadrigraphs are replaced at a late stage of the translation process,
after @command{m4} is run, so they do not get in the way of M4 quoting.
For example, the string <SAMP>`^@<:@'</SAMP>, independently of its quotation,
will appear as <SAMP>`^['</SAMP> in the output.
<P>
The empty quadrigraph can be used:
<UL>
<LI>to mark explicitly trailing spaces
Trailing spaces are smashed by @command{autom4te}. This is a feature.
<LI>to produce other quadrigraphs
For instance <SAMP>`@<@&t@:@'</SAMP> produces <SAMP>`@<:@'</SAMP>.
<LI>to escape <EM>occurrences</EM> of forbidden patterns
For instance you might want to mention <CODE>AC_FOO</CODE> is a comment, while
still being sure that @command{autom4te} will still catch unexpanded
<SAMP>`AC_*'</SAMP>. Then write <SAMP>`AC@&t@_FOO'</SAMP>.
</UL>
<P>
The name <SAMP>`@&t@'</SAMP> was suggested by Paul Eggert:
<BLOCKQUOTE>
<P>
I should give some credit to the <SAMP>`@&t@'</SAMP> pun. The <SAMP>`&'</SAMP> is my
own invention, but the <SAMP>`t'</SAMP> came from the source code of the
ALGOL68C compiler, written by Steve Bourne (of Bourne shell fame),
and which used <SAMP>`mt'</SAMP> to denote the empty string. In C, it would
have looked like something like:
<PRE>
char const mt[] = "";
</PRE>
<P>
but of course the source code was written in Algol 68.
<P>
I don't know where he got <SAMP>`mt'</SAMP> from: it could have been his own
invention, and I suppose it could have been a common pun around the
Cambridge University computer lab at the time.
</BLOCKQUOTE>
<H3><A NAME="SEC94" HREF="autoconf_toc.html#TOC94">Quotation Rule Of Thumb</A></H3>
<P>
To conclude, the quotation rule of thumb is:
<P>
<EM>One pair of quotes per pair of parentheses.</EM>
<P>
Never over-quote, never under-quote, in particular in the definition of
macros. In the few places where the macros need to use brackets
(usually in C program text or regular expressions), properly quote
<EM>the arguments</EM>!
<P>
It is common to read Autoconf programs with snippets like:
<PRE>
AC_TRY_LINK(
changequote(<<, >>)dnl
<<#include <time.h>
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif>>,
changequote([, ])dnl
[atoi (*tzname);], ac_cv_var_tzname=yes, ac_cv_var_tzname=no)
</PRE>
<P>
which is incredibly useless since <CODE>AC_TRY_LINK</CODE> is <EM>already</EM>
double quoting, so you just need:
<PRE>
AC_TRY_LINK(
[#include <time.h>
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif],
[atoi (*tzname);],
[ac_cv_var_tzname=yes],
[ac_cv_var_tzname=no])
</PRE>
<P>
The M4-fluent reader will note that these two examples are rigorously
equivalent, since <CODE>m4</CODE> swallows both the <SAMP>`changequote(<<, >>)'</SAMP>
and <SAMP>`<<'</SAMP> <SAMP>`>>'</SAMP> when it <EM>collects</EM> the arguments: these
quotes are not part of the arguments!
<P>
Simplified, the example above is just doing this:
<PRE>
changequote(<<, >>)dnl
<<[]>>
changequote([, ])dnl
</PRE>
<P>
instead of simply:
<PRE>
[[]]
</PRE>
<P>
With macros that do not double quote their arguments (which is the
rule), double-quote the (risky) literals:
<PRE>
AC_LINK_IFELSE([AC_LANG_PROGRAM(
[[#include <time.h>
#ifndef tzname /* For SGI. */
extern char *tzname[]; /* RS6000 and others reject char **tzname. */
#endif]],
[atoi (*tzname);])],
[ac_cv_var_tzname=yes],
[ac_cv_var_tzname=no])
</PRE>
<P>
See See section <A HREF="autoconf.html#SEC93">Quadrigraphs</A>, for what to do if you run into a hopeless case
where quoting does not suffice.
<P>
When you create a @command{configure} script using newly written macros,
examine it carefully to check whether you need to add more quotes in
your macros. If one or more words have disappeared in the <CODE>m4</CODE>
output, you need more quotes. When in doubt, quote.
<P>
However, it's also possible to put on too many layers of quotes. If
this happens, the resulting @command{configure} script will contain
unexpanded macros. The @command{autoconf} program checks for this problem
by doing <SAMP>`grep AC_ configure'</SAMP>.
<H2><A NAME="SEC95" HREF="autoconf_toc.html#TOC95">Invoking @command{autom4te}</A></H2>
<P>
The Autoconf suite, including M4sugar, M4sh, and Autotest in addition to
Autoconf per se, heavily rely on M4. All these different uses revealed
common needs factored into a layer over @command{m4}:
@command{autom4te}<A NAME="DOCF3" HREF="autoconf_foot.html#FOOT3">(3)</A>.
<P>
@command{autom4te} should basically considered as a replacement of
@command{m4} itself. In particular, its handling of command line
arguments is modeled after M4's:
<PRE>
autom4te <VAR>options</VAR> <VAR>files</VAR>
</PRE>
<P>
where the <VAR>files</VAR> are directly passed to @command{m4}. In addition
to the regular expansion, it handles the replacement of the quadrigraphs
(see section <A HREF="autoconf.html#SEC93">Quadrigraphs</A>), and of <SAMP>`__oline__'</SAMP>, the current line in the
output. It supports an extended syntax for the <VAR>files</VAR>:
<DL COMPACT>
<DT><TT>`<VAR>file</VAR>.m4f'</TT>
<DD>
This file is an M4 frozen file. Note that <EM>all the previous files
are ignored</EM>. See the option @option{--melt} for the rationale.
<DT><TT>`<VAR>file</VAR>?'</TT>
<DD>
If found in the library path, the <VAR>file</VAR> is included for expansion,
otherwise it is ignored instead of triggering a failure.
</DL>
<P>
Of course, it supports the Autoconf common subset of options:
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the command line options and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version number of Autoconf and exit.
<DT>@option{--verbose}
<DD>
<DT>@option{-v}
<DD>
Report processing steps.
<DT>@option{--debug}
<DD>
<DT>@option{-d}
<DD>
Don't remove the temporary files and be even more verbose.
<DT>@option{--include=<VAR>dir</VAR>}
<DD>
<DT>@option{-I <VAR>dir</VAR>}
<DD>
Also look for input files in <VAR>dir</VAR>. Multiple invocations
accumulate. Contrary to M4 but in agreement with common sense,
directories are browsed from last to first.
<DT>@option{--output=<VAR>file</VAR>}
<DD>
<DT>@option{-o <VAR>file</VAR>}
<DD>
Save output (script or trace) to <VAR>file</VAR>. The file @option{-} stands
for the standard output.
</DL>
<P>
As an extension of @command{m4}, it includes the following options:
<DL COMPACT>
<DT>@option{--warnings=<VAR>category</VAR>}
<DD>
<DT>@option{-W <VAR>category</VAR>}
<DD>
<A NAME="IDX632"></A>
Report the warnings related to <VAR>category</VAR> (which can actually be a
comma separated list). See section <A HREF="autoconf.html#SEC104">Reporting Messages</A>, macro
<CODE>AC_DIAGNOSE</CODE>, for a comprehensive list of categories. Special
values include:
<DL COMPACT>
<DT><SAMP>`all'</SAMP>
<DD>
report all the warnings
<DT><SAMP>`none'</SAMP>
<DD>
report none
<DT><SAMP>`error'</SAMP>
<DD>
treats warnings as errors
<DT><SAMP>`no-<VAR>category</VAR>'</SAMP>
<DD>
disable warnings falling into <VAR>category</VAR>
</DL>
Warnings about <SAMP>`syntax'</SAMP> are enabled by default, and the environment
variable <CODE>WARNINGS</CODE>, a comma separated list of categories, is
honored. @command{autom4te -W <VAR>category</VAR>} will actually
behave as if you had run:
<PRE>
autom4te --warnings=syntax,$WARNINGS,<VAR>category</VAR>
</PRE>
If you want to disable @command{autom4te}'s defaults and
<CODE>WARNINGS</CODE>, but (for example) enable the warnings about obsolete
constructs, you would use @option{-W none,obsolete}.
<A NAME="IDX633"></A>
<A NAME="IDX634"></A>
@command{autom4te} displays a back trace for errors, but not for
warnings; if you want them, just pass @option{-W error}. For instance,
on this <TT>`configure.ac'</TT>:
<PRE>
AC_DEFUN([INNER],
[AC_TRY_RUN([exit (0)])])
AC_DEFUN([OUTER],
[INNER])
AC_INIT
OUTER
</PRE>
you get:
<PRE>
$ <KBD>autom4te -l autoconf -Wcross</KBD>
configure.ac:8: warning: AC_TRY_RUN called without default \
to allow cross compiling
$ <KBD>autom4te -l autoconf -Wcross,error</KBD>
configure.ac:8: error: AC_TRY_RUN called without default \
to allow cross compiling
acgeneral.m4:3044: AC_TRY_RUN is expanded from...
configure.ac:2: INNER is expanded from...
configure.ac:5: OUTER is expanded from...
configure.ac:8: the top level
</PRE>
<DT>@option{--melt}
<DD>
<DT>@option{-m}
<DD>
Do not use frozen files. Any argument <CODE><VAR>file</VAR>.m4f</CODE> will be
replaced with <CODE><VAR>file</VAR>.m4</CODE>. This helps tracing the macros which
are executed only when the files are frozen, typically
<CODE>m4_define</CODE>. For instance, running:
<PRE>
autom4te --melt 1.m4 2.m4f 3.m4 4.m4f input.m4
</PRE>
is roughly equivalent to running:
<PRE>
m4 1.m4 2.m4 3.m4 4.m4 input.m4
</PRE>
while
<PRE>
autom4te 1.m4 2.m4f 3.m4 4.m4f input.m4
</PRE>
is equivalent to:
<PRE>
m4 --reload-state=4.m4f input.m4
</PRE>
<DT>@option{--freeze}
<DD>
<DT>@option{-f}
<DD>
Produce a frozen state file. @command{autom4te} freezing is stricter
than M4's: it must produce no warnings, and no output other than empty
lines (a line with white spaces is <EM>not</EM> empty) and comments
(starting with <SAMP>`#'</SAMP>). Please, note that contrary to @command{m4},
this options takes no argument:
<PRE>
autom4te 1.m4 2.m4 3.m4 --freeze --output=3.m4f
</PRE>
corresponds to
<PRE>
m4 1.m4 2.m4 3.m4 --freeze-state=3.m4f
</PRE>
<DT>@option{--mode=<VAR>octal-mode</VAR>}
<DD>
<DT>@option{-m <VAR>octal-mode</VAR>}
<DD>
Set the mode of the non traces output to <VAR>octal-mode</VAR>. By default,
<SAMP>`0666'</SAMP>.
</DL>
<P>
<A NAME="IDX635"></A>
As another additional feature over @command{m4}, @command{autom4te}
caches its results. GNU M4 is able to produce a regular output and
traces at the same time. Traces are heavily used in the GNU Build
System: @command{autoheader} uses them to build <TT>`config.h.in'</TT>,
@command{autoreconf} to determine what GNU Build System components are
used, @command{automake} to "parse" <TT>`configure.ac'</TT> etc. To save
the long runs of @command{m4}, traces are cached while performing
regular expansion, and conversely. This cache is (actually, the caches
are) stored in the directory <TT>`autom4te.cache'</TT>. <EM>It can safely
be removed</EM> at any moment (especially if for some reason
@command{autom4te} considers it is trashed).
<DL COMPACT>
<DT>@option{--force}
<DD>
<DT>@option{-f}
<DD>
Do not consider the cache (but update it anyway).
</DL>
<P>
Because traces are so important to the GNU Build System,
@command{autom4te} provides high level tracing features as compared to
M4, and helps exploiting the cache:
<DL COMPACT>
<DT>@option{--trace=<VAR>macro</VAR>[:<VAR>format</VAR>]}
<DD>
<DT>@option{-t <VAR>macro</VAR>[:<VAR>format</VAR>]}
<DD>
Trace the invocations to <VAR>macro</VAR> according to the <VAR>format</VAR>.
Multiple @option{--trace} arguments can be used to list several macros.
Multiple @option{--trace} arguments for a single macro are not
cumulative; instead, you should just make <VAR>format</VAR> as long as
needed.
The <VAR>format</VAR> is a regular string, with newlines if desired, and
several special escape codes. It defaults to <SAMP>`$f:$l:$n:$%'</SAMP>. It can
use the following special escapes:
<DL COMPACT>
<DT><SAMP>`$$'</SAMP>
<DD>
The character <SAMP>`$'</SAMP>.
<DT><SAMP>`$f'</SAMP>
<DD>
The filename from which <VAR>macro</VAR> is called.
<DT><SAMP>`$l'</SAMP>
<DD>
The line number from which <VAR>macro</VAR> is called.
<DT><SAMP>`$d'</SAMP>
<DD>
The depth of the <VAR>macro</VAR> call. This is an M4 technical detail that
you probably don't want to know about.
<DT><SAMP>`$n'</SAMP>
<DD>
The name of the <VAR>macro</VAR>.
<DT><SAMP>`$<VAR>num</VAR>'</SAMP>
<DD>
The <VAR>num</VAR>th argument of the call to <VAR>macro</VAR>.
<DT><SAMP>`$@'</SAMP>
<DD>
<DT><SAMP>`$<VAR>sep</VAR>@'</SAMP>
<DD>
<DT><SAMP>`${<VAR>separator</VAR>}@'</SAMP>
<DD>
All the arguments passed to <VAR>macro</VAR>, separated by the character
<VAR>sep</VAR> or the string <VAR>separator</VAR> (<SAMP>`,'</SAMP> by default). Each
argument is quoted, i.e. enclosed in a pair of square brackets.
<DT><SAMP>`$*'</SAMP>
<DD>
<DT><SAMP>`$<VAR>sep</VAR>*'</SAMP>
<DD>
<DT><SAMP>`${<VAR>separator</VAR>}*'</SAMP>
<DD>
As above, but the arguments are not quoted.
<DT><SAMP>`$%'</SAMP>
<DD>
<DT><SAMP>`$<VAR>sep</VAR>%'</SAMP>
<DD>
<DT><SAMP>`${<VAR>separator</VAR>}%'</SAMP>
<DD>
As above, but the arguments are not quoted, all new line characters in
the arguments are smashed, and the default separator is <SAMP>`:'</SAMP>.
The escape <SAMP>`$%'</SAMP> produces single-line trace outputs (unless you put
newlines in the <SAMP>`separator'</SAMP>), while <SAMP>`$@'</SAMP> and <SAMP>`$*'</SAMP> do
not.
</DL>
See section <A HREF="autoconf.html#SEC13">Using @command{autoconf} to Create @command{configure}</A>, for examples of trace uses.
<DT>@option{--preselect=<VAR>macro</VAR>}
<DD>
<DT>@option{-p <VAR>macro</VAR>}
<DD>
Cache the traces of <VAR>macro</VAR>, but do not enable traces. This is
especially important to save cpu cycles in the future. For instance,
when invoked, @command{autoconf} preselects all the macros that
@command{autoheader}, <CODE>automake</CODE>, <CODE>autoreconf</CODE> etc. will
trace, so that running @command{m4} is not needed to trace them: the
cache suffices. This results in a huge speed-up.
</DL>
<P>
<A NAME="IDX636"></A>
Finally, @command{autom4te} introduces the concept of @dfn{Autom4te
libraries}. They consists in a powerful yet extremely simple feature:
sets of combined command line arguments:
<DL COMPACT>
<DT>@option{--language=<VAR>language</VAR>}
<DD>
<DT>@option{-l =<VAR>language</VAR>}
<DD>
Use the <VAR>language</VAR> Autom4te library. Current languages include:
<DL COMPACT>
<DT><CODE>M4sugar</CODE>
<DD>
create M4sugar output.
<DT><CODE>M4sh</CODE>
<DD>
create M4sh executable shell scripts.
<DT><CODE>Autotest</CODE>
<DD>
create Autotest executable test suites.
<DT><CODE>Autoconf</CODE>
<DD>
create Autoconf executable configure scripts.
</DL>
</DL>
<P>
<A NAME="IDX637"></A>
As an example, if Autoconf is installed in its default location,
<TT>`/usr/local'</TT>, running <SAMP>`autom4te -l m4sugar foo.m4'</SAMP> is strictly
equivalent to running <SAMP>`autom4te --include /usr/local/share/autoconf
m4sugar/m4sugar.m4f --warning syntax foo.m4'</SAMP>. Recursive expansion
applies: running <SAMP>`autom4te -l m4sh foo.m4'</SAMP>, is the same as
<SAMP>`autom4te --language M4sugar m4sugar/m4sh.m4f foo.m4'</SAMP>, i.e.,
<SAMP>`autom4te --include /usr/local/share/autoconf m4sugar/m4sugar.m4f
m4sugar/m4sh.m4f --mode 777 foo.m4'</SAMP>. The definition of the languages is
stored in <TT>`autom4te.cfg'</TT>.
<H2><A NAME="SEC96" HREF="autoconf_toc.html#TOC96">Programming in M4sugar</A></H2>
<P>
<A NAME="IDX638"></A>
M4 by itself provides only a small, but sufficient, set of all-purpose
macros. M4sugar introduces additional generic macros. Its name was
coined by Lars J. Aas: "Readability And Greater Understanding Stands 4
M4sugar".
<H3><A NAME="SEC97" HREF="autoconf_toc.html#TOC97">Redefined M4 Macros</A></H3>
<P>
With a few exceptions, all the M4 native macros are moved in the
<SAMP>`m4_'</SAMP> pseudo-namespace, e.g., M4sugar renames <CODE>define</CODE> as
<CODE>m4_define</CODE> etc.
<P>
Some M4 macros are redefined, and are slightly incompatible with their
native equivalent.
<P>
<DL>
<DT><U>Macro:</U> <B>dnl</B>
<DD><A NAME="IDX639"></A>
<A NAME="IDX640"></A>
This macro kept its original name: no <CODE>m4_dnl</CODE> is defined.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_defn</B> <I>(<VAR>macro</VAR>)</I>
<DD><A NAME="IDX641"></A>
<A NAME="IDX642"></A>
Contrary to the M4 builtin, this macro fails if <VAR>macro</VAR> is not
defined. See <CODE>m4_undefine</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_exit</B> <I>(<VAR>exit-status</VAR>)</I>
<DD><A NAME="IDX643"></A>
<A NAME="IDX644"></A>
This macro corresponds to <CODE>m4exit</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_if</B> <I>(<VAR>comment</VAR>)</I>
<DD><A NAME="IDX645"></A>
<DT><U>Macro:</U> <B>m4_if</B> <I>(<VAR>string-1</VAR>, <VAR>string-2</VAR>, <VAR>equal</VAR>, @ovar{not-equal})</I>
<DD><A NAME="IDX646"></A>
<DT><U>Macro:</U> <B>m4_if</B> <I>(<VAR>string-1</VAR>, <VAR>string-2</VAR>, <VAR>equal</VAR>, ...)</I>
<DD><A NAME="IDX647"></A>
<A NAME="IDX648"></A>
This macro corresponds to <CODE>ifelse</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_undefine</B> <I>(<VAR>macro</VAR>)</I>
<DD><A NAME="IDX649"></A>
<A NAME="IDX650"></A>
Contrary to the M4 builtin, this macro fails if <VAR>macro</VAR> is not
defined. Use
<PRE>
m4_ifdef([<VAR>macro</VAR>], [m4_undefine([<VAR>macro</VAR>])])
</PRE>
<P>
to recover the behavior of the builtin.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_bpatsubst</B> <I>(<VAR>string</VAR>, <VAR>regexp</VAR>, @ovar{replacement})</I>
<DD><A NAME="IDX651"></A>
<A NAME="IDX652"></A>
This macro corresponds to <CODE>patsubst</CODE>. The name <CODE>m4_patsubst</CODE>
is kept for future versions of M4sh, on top of GNU M4 which will
provide extended regular expression syntax via <CODE>epatsubst</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_popdef</B> <I>(<VAR>macro</VAR>)</I>
<DD><A NAME="IDX653"></A>
<A NAME="IDX654"></A>
Contrary to the M4 builtin, this macro fails if <VAR>macro</VAR> is not
defined. See <CODE>m4_undefine</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_bregexp</B> <I>(<VAR>string</VAR>, <VAR>regexp</VAR>, @ovar{replacement})</I>
<DD><A NAME="IDX655"></A>
<A NAME="IDX656"></A>
This macro corresponds to <CODE>regexp</CODE>. The name <CODE>m4_regexp</CODE>
is kept for future versions of M4sh, on top of GNU M4 which will
provide extended regular expression syntax via <CODE>eregexp</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_wrap</B> <I>(<VAR>text</VAR>)</I>
<DD><A NAME="IDX657"></A>
<A NAME="IDX658"></A>
This macro corresponds to <CODE>m4wrap</CODE>.
<P>
You are encouraged to end <VAR>text</VAR> with <SAMP>`[]'</SAMP>, so that there are
no risks that two consecutive invocations of <CODE>m4_wrap</CODE> result in an
unexpected pasting of tokens, as in
<PRE>
m4_define([foo], [Foo])
m4_define([bar], [Bar])
m4_define([foobar], [FOOBAR])
m4_wrap([bar])
m4_wrap([foo])
=>FOOBAR
</PRE>
</DL>
<H3><A NAME="SEC98" HREF="autoconf_toc.html#TOC98">Evaluation Macros</A></H3>
<P>
The following macros give some control over the order of the evaluation
by adding or removing levels of quotes. They are meant for hard core M4
programmers.
<P>
<DL>
<DT><U>Macro:</U> <B>m4_dquote</B> <I>(<VAR>arg1</VAR>, ...)</I>
<DD><A NAME="IDX659"></A>
<A NAME="IDX660"></A>
Return the arguments as a quoted list of quoted arguments.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>m4_quote</B> <I>(<VAR>arg1</VAR>, ...)</I>
<DD><A NAME="IDX661"></A>
<A NAME="IDX662"></A>
Return the arguments as a single entity, i.e., wrap them into a pair of
quotes.
</DL>
<P>
The following example aims at emphasing the difference between (i), not
using these macros, (ii), using <CODE>m4_quote</CODE>, and (iii), using
<CODE>m4_dquote</CODE>.
<PRE>
$ <KBD>cat example.m4</KBD>
# Over quote, so that quotes are visible.
m4_define([show], [$[]1 = [$1], $[]@ = [$@]])
m4_divert(0)dnl
show(a, b)
show(m4_quote(a, b))
show(m4_dquote(a, b))
$ <KBD>autom4te -l m4sugar example.m4</KBD>
$1 = a, $@ = [a],[b]
$1 = a,b, $@ = [a,b]
$1 = [a],[b], $@ = [[a],[b]]
</PRE>
<H3><A NAME="SEC99" HREF="autoconf_toc.html#TOC99">Forbidden Patterns</A></H3>
<P>
M4sugar provides a means to define suspicious patterns, patterns
describing tokens which should not be found in the output. For
instance, if an Autoconf <TT>`configure'</TT> script includes tokens such as
<SAMP>`AC_DEFINE'</SAMP>, or <SAMP>`dnl'</SAMP>, then most probably something went
wrong (typically a macro was not evaluated because of over quotation).
<P>
M4sugar forbids all the tokens matching <SAMP>`^m4_'</SAMP> and <SAMP>`^dnl$'</SAMP>.
<P>
<DL>
<DT><U>Macro:</U> <B>m4_pattern_forbid</B> <I>(<VAR>pattern</VAR>)</I>
<DD><A NAME="IDX663"></A>
<A NAME="IDX664"></A>
Declare no token matching <VAR>pattern</VAR> must be found in the output.
Comments are not checked; this can be a problem if, for instance, you
have some macro left unexpanded after an <SAMP>`#include'</SAMP>. No consensus
is currently found in the Autoconf community, as some people consider it
should be valid to name macros in comments (which doesn't makes sense to
the author of this documentation, as <SAMP>`#'</SAMP>-comments should document
the output, not the input, documented vy <SAMP>`dnl'</SAMP>-comments).
</DL>
<P>
Of course, you might encounter exceptions to these generic rules, for
instance you might have to refer to <SAMP>`$m4_flags'</SAMP>.
<P>
<DL>
<DT><U>Macro:</U> <B>m4_pattern_allow</B> <I>(<VAR>pattern</VAR>)</I>
<DD><A NAME="IDX665"></A>
<A NAME="IDX666"></A>
Any token matching <VAR>pattern</VAR> is allowed, including if it matches an
<CODE>m4_pattern_forbid</CODE> pattern.
</DL>
<H2><A NAME="SEC100" HREF="autoconf_toc.html#TOC100">Programming in M4sh</A></H2>
<P>
M4sh provides portable alternatives for some common shell constructs
that unfortunately are not portable in practice.
<P>
<DL>
<DT><U>Macro:</U> <B>AS_DIRNAME</B> <I>(<VAR>pathname</VAR>)</I>
<DD><A NAME="IDX667"></A>
<A NAME="IDX668"></A>
Return the directory portion of <VAR>pathname</VAR>, using the algorithm
required by POSIX. See section <A HREF="autoconf.html#SEC119">Limitations of Usual Tools</A>, for more
details about what this returns and why it is more portable than the
@command{dirname} command.
</DL>
<H1><A NAME="SEC101" HREF="autoconf_toc.html#TOC101">Writing Autoconf Macros</A></H1>
<P>
When you write a feature test that could be applicable to more than one
software package, the best thing to do is encapsulate it in a new macro.
Here are some instructions and guidelines for writing Autoconf macros.
<H2><A NAME="SEC102" HREF="autoconf_toc.html#TOC102">Macro Definitions</A></H2>
<P>
<A NAME="IDX669"></A>
Autoconf macros are defined using the <CODE>AC_DEFUN</CODE> macro, which is
similar to the M4 builtin <CODE>m4_define</CODE> macro. In addition to
defining a macro, <CODE>AC_DEFUN</CODE> adds to it some code that is used to
constrain the order in which macros are called (see section <A HREF="autoconf.html#SEC106">Prerequisite Macros</A>).
<P>
An Autoconf macro definition looks like this:
<PRE>
AC_DEFUN(<VAR>macro-name</VAR>, <VAR>macro-body</VAR>)
</PRE>
<P>
You can refer to any arguments passed to the macro as <SAMP>`$1'</SAMP>,
<SAMP>`$2'</SAMP>, etc. See section `How to define new macros' in <CITE>GNU m4</CITE>, for more complete information on writing M4 macros.
<P>
Be sure to properly quote both the <VAR>macro-body</VAR> <EM>and</EM> the
<VAR>macro-name</VAR> to avoid any problems if the macro happens to have
been previously defined.
<P>
Each macro should have a header comment that gives its prototype, and a
brief description. When arguments have default values, display them in
the prototype. For example:
<PRE>
# AC_MSG_ERROR(ERROR, [EXIT-STATUS = 1])
# --------------------------------------
m4_define([AC_MSG_ERROR],
[{ _AC_ECHO([configure: error: $1], 2); exit m4_default([$2], 1); }])
</PRE>
<P>
Comments about the macro should be left in the header comment. Most
other comments will make their way into <TT>`configure'</TT>, so just keep
using <SAMP>`#'</SAMP> to introduce comments.
<P>
<A NAME="IDX670"></A>
If you have some very special comments about pure M4 code, comments
that make no sense in <TT>`configure'</TT> and in the header comment, then
use the builtin <CODE>dnl</CODE>: it causes <CODE>m4</CODE> to discard the text
through the next newline.
<P>
Keep in mind that <CODE>dnl</CODE> is rarely needed to introduce comments;
<CODE>dnl</CODE> is more useful to get rid of the newlines following macros
that produce no output, such as <CODE>AC_REQUIRE</CODE>.
<H2><A NAME="SEC103" HREF="autoconf_toc.html#TOC103">Macro Names</A></H2>
<P>
All of the Autoconf macros have all-uppercase names starting with
<SAMP>`AC_'</SAMP> to prevent them from accidentally conflicting with other
text. All shell variables that they use for internal purposes have
mostly-lowercase names starting with <SAMP>`ac_'</SAMP>. To ensure that your
macros don't conflict with present or future Autoconf macros, you should
prefix your own macro names and any shell variables they use with some
other sequence. Possibilities include your initials, or an abbreviation
for the name of your organization or software package.
<P>
Most of the Autoconf macros' names follow a structured naming convention
that indicates the kind of feature check by the name. The macro names
consist of several words, separated by underscores, going from most
general to most specific. The names of their cache variables use the
same convention (see section <A HREF="autoconf.html#SEC83">Cache Variable Names</A>, for more information on
them).
<P>
The first word of the name after <SAMP>`AC_'</SAMP> usually tells the category
of feature being tested. Here are the categories used in Autoconf for
specific test macros, the kind of macro that you are more likely to
write. They are also used for cache variables, in all-lowercase. Use
them where applicable; where they're not, invent your own categories.
<DL COMPACT>
<DT><CODE>C</CODE>
<DD>
C language builtin features.
<DT><CODE>DECL</CODE>
<DD>
Declarations of C variables in header files.
<DT><CODE>FUNC</CODE>
<DD>
Functions in libraries.
<DT><CODE>GROUP</CODE>
<DD>
UNIX group owners of files.
<DT><CODE>HEADER</CODE>
<DD>
Header files.
<DT><CODE>LIB</CODE>
<DD>
C libraries.
<DT><CODE>PATH</CODE>
<DD>
The full path names to files, including programs.
<DT><CODE>PROG</CODE>
<DD>
The base names of programs.
<DT><CODE>MEMBER</CODE>
<DD>
Members of aggregates.
<DT><CODE>SYS</CODE>
<DD>
Operating system features.
<DT><CODE>TYPE</CODE>
<DD>
C builtin or declared types.
<DT><CODE>VAR</CODE>
<DD>
C variables in libraries.
</DL>
<P>
After the category comes the name of the particular feature being
tested. Any further words in the macro name indicate particular aspects
of the feature. For example, <CODE>AC_FUNC_UTIME_NULL</CODE> checks the
behavior of the <CODE>utime</CODE> function when called with a <CODE>NULL</CODE>
pointer.
<P>
An internal macro should have a name that starts with an underscore;
Autoconf internals should therefore start with <SAMP>`_AC_'</SAMP>.
Additionally, a macro that is an internal subroutine of another macro
should have a name that starts with an underscore and the name of that
other macro, followed by one or more words saying what the internal
macro does. For example, <CODE>AC_PATH_X</CODE> has internal macros
<CODE>_AC_PATH_X_XMKMF</CODE> and <CODE>_AC_PATH_X_DIRECT</CODE>.
<H2><A NAME="SEC104" HREF="autoconf_toc.html#TOC104">Reporting Messages</A></H2>
<P>
<A NAME="IDX671"></A>
<P>
When macros statically diagnose abnormal situations, benign or fatal,
they should report them using these macros. For dynamic issues, i.e.,
when @command{configure} is run, see section <A HREF="autoconf.html#SEC86">Printing Messages</A>.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_DIAGNOSE</B> <I>(<VAR>category</VAR>, <VAR>message</VAR>)</I>
<DD><A NAME="IDX672"></A>
<A NAME="IDX673"></A>
Report <VAR>message</VAR> as a warning (or as an error if requested by the
user) if it falls into the <VAR>category</VAR>. You are encouraged to use
standard categories, which currently include:
<DL COMPACT>
<DT><SAMP>`all'</SAMP>
<DD>
messages that don't fall into one of the following category. Use of an
empty <VAR>category</VAR> is equivalent.
<DT><SAMP>`cross'</SAMP>
<DD>
related to cross compilation issues.
<DT><SAMP>`obsolete'</SAMP>
<DD>
use of an obsolete construct.
<DT><SAMP>`syntax'</SAMP>
<DD>
dubious syntactic constructs, incorrectly ordered macro calls.
</DL>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_WARNING</B> <I>(<VAR>message</VAR>)</I>
<DD><A NAME="IDX674"></A>
<A NAME="IDX675"></A>
Equivalent to <SAMP>`AC_DIAGNOSE([syntax], <VAR>message</VAR>)'</SAMP>, but you are
strongly encouraged to use a finer grained category.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_FATAL</B> <I>(<VAR>message</VAR>)</I>
<DD><A NAME="IDX676"></A>
<A NAME="IDX677"></A>
Report a severe error <VAR>message</VAR>, and have @command{autoconf} die.
</DL>
<P>
When the user runs <SAMP>`autoconf -W error'</SAMP>, warnings from
<CODE>AC_DIAGNOSE</CODE> and <CODE>AC_WARNING</CODE> are reported as error, see
section <A HREF="autoconf.html#SEC13">Using @command{autoconf} to Create @command{configure}</A>.
<H2><A NAME="SEC105" HREF="autoconf_toc.html#TOC105">Dependencies Between Macros</A></H2>
<P>
Some Autoconf macros depend on other macros having been called first in
order to work correctly. Autoconf provides a way to ensure that certain
macros are called if needed and a way to warn the user if macros are
called in an order that might cause incorrect operation.
<H3><A NAME="SEC106" HREF="autoconf_toc.html#TOC106">Prerequisite Macros</A></H3>
<P>
A macro that you write might need to use values that have previously
been computed by other macros. For example, <CODE>AC_DECL_YYTEXT</CODE>
examines the output of <CODE>flex</CODE> or <CODE>lex</CODE>, so it depends on
<CODE>AC_PROG_LEX</CODE> having been called first to set the shell variable
<CODE>LEX</CODE>.
<P>
Rather than forcing the user of the macros to keep track of the
dependencies between them, you can use the <CODE>AC_REQUIRE</CODE> macro to do
it automatically. <CODE>AC_REQUIRE</CODE> can ensure that a macro is only
called if it is needed, and only called once.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_REQUIRE</B> <I>(<VAR>macro-name</VAR>)</I>
<DD><A NAME="IDX678"></A>
<A NAME="IDX679"></A>
If the M4 macro <VAR>macro-name</VAR> has not already been called, call it
(without any arguments). Make sure to quote <VAR>macro-name</VAR> with
square brackets. <VAR>macro-name</VAR> must have been defined using
<CODE>AC_DEFUN</CODE> or else contain a call to <CODE>AC_PROVIDE</CODE> to indicate
that it has been called.
<P>
<CODE>AC_REQUIRE</CODE> must be used inside an <CODE>AC_DEFUN</CODE>'d macro; it
must not be called from the top level.
</DL>
<P>
<CODE>AC_REQUIRE</CODE> is often misunderstood. It really implements
dependencies between macros in the sense that if one macro depends upon
another, the latter will be expanded <EM>before</EM> the body of the
former. In particular, <SAMP>`AC_REQUIRE(FOO)'</SAMP> is not replaced with the
body of <CODE>FOO</CODE>. For instance, this definition of macros:
<PRE>
AC_DEFUN([TRAVOLTA],
[test "$body_temparature_in_celsius" -gt "38" &&
dance_floor=occupied])
AC_DEFUN([NEWTON_JOHN],
[test "$hair_style" = "curly" &&
dance_floor=occupied])
AC_DEFUN([RESERVE_DANCE_FLOOR],
[if date | grep '^Sat.*pm' >/dev/null 2>&1; then
AC_REQUIRE([TRAVOLTA])
AC_REQUIRE([NEWTON_JOHN])
fi])
</PRE>
<P>
with this <TT>`configure.ac'</TT>
<PRE>
AC_INIT
RESERVE_DANCE_FLOOR
if test "$dance_floor" = occupied; then
AC_MSG_ERROR([cannot pick up here, let's move])
fi
</PRE>
<P>
will not leave you with a better chance to meet a kindred soul at
other times than Saturday night since it expands into:
<PRE>
test "$body_temperature_in_Celsius" -gt "38" &&
dance_floor=occupied
test "$hair_style" = "curly" &&
dance_floor=occupied
fi
if date | grep '^Sat.*pm' >/dev/null 2>&1; then
fi
</PRE>
<P>
This behavior was chosen on purpose: (i) it prevents messages in
required macros from interrupting the messages in the requiring macros;
(ii) it avoids bad surprises when shell conditionals are used, as in:
<PRE>
if ...; then
AC_REQUIRE([SOME_CHECK])
fi
...
SOME_CHECK
</PRE>
<P>
You are encouraged to put all <CODE>AC_REQUIRE</CODE>s at the beginning of a
macro. You can use <CODE>dnl</CODE> to avoid the empty lines they leave.
<H3><A NAME="SEC107" HREF="autoconf_toc.html#TOC107">Suggested Ordering</A></H3>
<P>
Some macros should be run before another macro if both are called, but
neither <EM>requires</EM> that the other be called. For example, a macro
that changes the behavior of the C compiler should be called before any
macros that run the C compiler. Many of these dependencies are noted in
the documentation.
<P>
Autoconf provides the <CODE>AC_BEFORE</CODE> macro to warn users when macros
with this kind of dependency appear out of order in a
<TT>`configure.ac'</TT> file. The warning occurs when creating
@command{configure} from <TT>`configure.ac'</TT>, not when running
@command{configure}.
<P>
For example, <CODE>AC_PROG_CPP</CODE> checks whether the C compiler
can run the C preprocessor when given the @option{-E} option. It should
therefore be called after any macros that change which C compiler is
being used, such as <CODE>AC_PROG_CC</CODE>. So <CODE>AC_PROG_CC</CODE> contains:
<PRE>
AC_BEFORE([$0], [AC_PROG_CPP])dnl
</PRE>
<P>
This warns the user if a call to <CODE>AC_PROG_CPP</CODE> has already occurred
when <CODE>AC_PROG_CC</CODE> is called.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_BEFORE</B> <I>(<VAR>this-macro-name</VAR>, <VAR>called-macro-name</VAR>)</I>
<DD><A NAME="IDX680"></A>
<A NAME="IDX681"></A>
Make <CODE>m4</CODE> print a warning message to the standard error output if
<VAR>called-macro-name</VAR> has already been called. <VAR>this-macro-name</VAR>
should be the name of the macro that is calling <CODE>AC_BEFORE</CODE>. The
macro <VAR>called-macro-name</VAR> must have been defined using
<CODE>AC_DEFUN</CODE> or else contain a call to <CODE>AC_PROVIDE</CODE> to indicate
that it has been called.
</DL>
<H2><A NAME="SEC108" HREF="autoconf_toc.html#TOC108">Obsoleting Macros</A></H2>
<P>
Configuration and portability technology has evolved over the years.
Often better ways of solving a particular problem are developed, or
ad-hoc approaches are systematized. This process has occurred in many
parts of Autoconf. One result is that some of the macros are now
considered <EM>obsolete</EM>; they still work, but are no longer considered
the best thing to do, hence they should be replaced with more modern
macros. Ideally, @command{autoupdate} should substitute the old macro calls
with their modern implementation.
<P>
Autoconf provides a simple means to obsolete a macro.
<P>
<DL>
<DT><U>Macro:</U> <B>AU_DEFUN</B> <I>(<VAR>old-macro</VAR>, <VAR>implementation</VAR>, @ovar{message})</I>
<DD><A NAME="IDX682"></A>
<A NAME="IDX683"></A>
<A NAME="IDX684"></A>
Define <VAR>old-macro</VAR> as <VAR>implementation</VAR>. The only difference
with <CODE>AC_DEFUN</CODE> is that the user will be warned that
<VAR>old-macro</VAR> is now obsolete.
<P>
If she then uses @command{autoupdate}, the call to <VAR>old-macro</VAR> will be
replaced by the modern <VAR>implementation</VAR>. The additional
<VAR>message</VAR> is then printed.
</DL>
<H2><A NAME="SEC109" HREF="autoconf_toc.html#TOC109">Coding Style</A></H2>
<P>
The Autoconf macros follow a strict coding style. You are encouraged to
follow this style, especially if you intend to distribute your macro,
either by contributing it to Autoconf itself, or via other means.
<P>
The first requirement is to pay great attention to the quotation, for
more details, see section <A HREF="autoconf.html#SEC9">The Autoconf Language</A>, and section <A HREF="autoconf.html#SEC88">M4 Quotation</A>.
<P>
Do not try to invent new interfaces. It is likely that there is a macro
in Autoconf that resembles the macro you are defining: try to stick to
this existing interface (order of arguments, default values, etc.). We
<EM>are</EM> conscious that some of these interfaces are not perfect;
nevertheless, when harmless, homogeneity should be preferred over
creativity.
<P>
Be careful about clashes both between M4 symbols and between shell
variables.
<P>
If you stick to the suggested M4 naming scheme (see section <A HREF="autoconf.html#SEC103">Macro Names</A>),
you are unlikely to generate conflicts. Nevertheless, when you need to
set a special value, <EM>avoid using a regular macro name</EM>; rather,
use an "impossible" name. For instance, up to version 2.13, the macro
<CODE>AC_SUBST</CODE> used to remember what <VAR>symbol</VAR>s were already defined
by setting <CODE>AC_SUBST_<VAR>symbol</VAR></CODE>, which is a regular macro name.
But since there is a macro named <CODE>AC_SUBST_FILE</CODE>, it was just
impossible to <SAMP>`AC_SUBST(FILE)'</SAMP>! In this case,
<CODE>AC_SUBST(<VAR>symbol</VAR>)</CODE> or <CODE>_AC_SUBST(<VAR>symbol</VAR>)</CODE> should
have been used (yes, with the parentheses)...or better yet, high-level
macros such as <CODE>AC_EXPAND_ONCE</CODE>.
<P>
No Autoconf macro should ever enter the user-variable name space; i.e.,
except for the variables that are the actual result of running the
macro, all shell variables should start with <CODE>ac_</CODE>. In
addition, small macros or any macro that is likely to be embedded in
other macros should be careful not to use obvious names.
<P>
<A NAME="IDX685"></A>
Do not use <CODE>dnl</CODE> to introduce comments: most of the comments you
are likely to write are either header comments which are not output
anyway, or comments that should make their way into <TT>`configure'</TT>.
There are exceptional cases where you do want to comment special M4
constructs, in which case <CODE>dnl</CODE> is right, but keep in mind that it
is unlikely.
<P>
M4 ignores the leading spaces before each argument, use this feature to
indent in such a way that arguments are (more or less) aligned with the
opening parenthesis of the macro being called. For instance, instead of
<PRE>
AC_CACHE_CHECK(for EMX OS/2 environment,
ac_cv_emxos2,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM(, [return __EMX__;])],
[ac_cv_emxos2=yes], [ac_cv_emxos2=no])])
</PRE>
<P>
write
<PRE>
AC_CACHE_CHECK([for EMX OS/2 environment], [ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
</PRE>
<P>
or even
<PRE>
AC_CACHE_CHECK([for EMX OS/2 environment],
[ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
[return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
</PRE>
<P>
When using <CODE>AC_TRY_RUN</CODE> or any macro that cannot work when
cross-compiling, provide a pessimistic value (typically <SAMP>`no'</SAMP>).
<P>
Feel free to use various tricks to prevent auxiliary tools, such as
syntax-highlighting editors, from behaving improperly. For instance,
instead of:
<PRE>
m4_bpatsubst([$1], [$"])
</PRE>
<P>
use
<PRE>
m4_bpatsubst([$1], [$""])
</PRE>
<P>
so that Emacsen do not open a endless "string" at the first quote.
For the same reasons, avoid:
<PRE>
test $[#] != 0
</PRE>
<P>
and use:
<PRE>
test $[@%:@] != 0
</PRE>
<P>
Otherwise, the closing bracket would be hidden inside a <SAMP>`#'</SAMP>-comment,
breaking the bracket-matching highlighting from Emacsen. Note the
preferred style to escape from M4: <SAMP>`$[1]'</SAMP>, <SAMP>`$[@]'</SAMP>, etc. Do
not escape when it is unneeded. Common examples of useless quotation
are <SAMP>`[$]$1'</SAMP> (write <SAMP>`$$1'</SAMP>), <SAMP>`[$]var'</SAMP> (use <SAMP>`$var'</SAMP>),
etc. If you add portability issues to the picture, you'll prefer
<SAMP>`${1+"$[@]"}'</SAMP> to <SAMP>`"[$]@"'</SAMP>, and you'll prefer do something
better than hacking Autoconf <CODE>:-)</CODE>.
<P>
When using @command{sed}, don't use @option{-e} except for indenting
purpose. With the <CODE>s</CODE> command, the preferred separator is <SAMP>`/'</SAMP>
unless <SAMP>`/'</SAMP> itself is used in the command, in which case you should
use <SAMP>`,'</SAMP>.
<P>
See section <A HREF="autoconf.html#SEC102">Macro Definitions</A>, for details on how to define a macro. If a
macro doesn't use <CODE>AC_REQUIRE</CODE> and it is expected to never be the
object of an <CODE>AC_REQUIRE</CODE> directive, then use <CODE>define</CODE>. In
case of doubt, use <CODE>AC_DEFUN</CODE>. All the <CODE>AC_REQUIRE</CODE>
statements should be at the beginning of the macro, <CODE>dnl</CODE>'ed.
<P>
You should not rely on the number of arguments: instead of checking
whether an argument is missing, test that it is not empty. It provides
both a simpler and a more predictable interface to the user, and saves
room for further arguments.
<P>
Unless the macro is short, try to leave the closing <SAMP>`])'</SAMP> at the
beginning of a line, followed by a comment that repeats the name of the
macro being defined. This introduces an additional newline in
@command{configure}; normally, that is not a problem, but if you want to
remove it you can use <SAMP>`[]dnl'</SAMP> on the last line. You can similarly
use <SAMP>`[]dnl'</SAMP> after a macro call to remove its newline. <SAMP>`[]dnl'</SAMP>
is recommended instead of <SAMP>`dnl'</SAMP> to ensure that M4 does not
interpret the <SAMP>`dnl'</SAMP> as being attached to the preceding text or
macro output. For example, instead of:
<PRE>
AC_DEFUN([AC_PATH_X],
[AC_MSG_CHECKING([for X])
AC_REQUIRE_CPP()
# ...omitted...
AC_MSG_RESULT([libraries $x_libraries, headers $x_includes])
fi])
</PRE>
<P>
you would write:
<PRE>
AC_DEFUN([AC_PATH_X],
[AC_REQUIRE_CPP()[]dnl
AC_MSG_CHECKING([for X])
# ...omitted...
AC_MSG_RESULT([libraries $x_libraries, headers $x_includes])
fi[]dnl
])# AC_PATH_X
</PRE>
<P>
If the macro is long, try to split it into logical chunks. Typically,
macros that check for a bug in a function and prepare its
<CODE>AC_LIBOBJ</CODE> replacement should have an auxiliary macro to perform
this setup. Do not hesitate to introduce auxiliary macros to factor
your code.
<P>
In order to highlight the recommended coding style, here is a macro
written the old way:
<PRE>
dnl Check for EMX on OS/2.
dnl _AC_EMXOS2
AC_DEFUN(_AC_EMXOS2,
[AC_CACHE_CHECK(for EMX OS/2 environment, ac_cv_emxos2,
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM(, return __EMX__;)],
ac_cv_emxos2=yes, ac_cv_emxos2=no)])
test "$ac_cv_emxos2" = yes && EMXOS2=yes])
</PRE>
<P>
and the new way:
<PRE>
# _AC_EMXOS2
# ----------
# Check for EMX on OS/2.
define([_AC_EMXOS2],
[AC_CACHE_CHECK([for EMX OS/2 environment], [ac_cv_emxos2],
[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [return __EMX__;])],
[ac_cv_emxos2=yes],
[ac_cv_emxos2=no])])
test "$ac_cv_emxos2" = yes && EMXOS2=yes[]dnl
])# _AC_EMXOS2
</PRE>
<H1><A NAME="SEC110" HREF="autoconf_toc.html#TOC110">Portable Shell Programming</A></H1>
<P>
When writing your own checks, there are some shell-script programming
techniques you should avoid in order to make your code portable. The
Bourne shell and upward-compatible shells like the Korn shell and Bash
have evolved over the years, but to prevent trouble, do not take
advantage of features that were added after UNIX version 7, circa
1977. You should not use shell functions, aliases, negated character
classes, or other features that are not found in all Bourne-compatible
shells; restrict yourself to the lowest common denominator. Even
<CODE>unset</CODE> is not supported by all shells! Also, include a space
after the exclamation point in interpreter specifications, like this:
<PRE>
#! /usr/bin/perl
</PRE>
<P>
If you omit the space before the path, then 4.2BSD based systems
(such as Sequent DYNIX) will ignore the line, because they interpret
<SAMP>`#! /'</SAMP> as a 4-byte magic number. Some old systems have quite
small limits on the length of the <SAMP>`#!'</SAMP> line too, for instance 32
bytes (not including the newline) on SunOS 4.
<P>
The set of external programs you should run in a @command{configure} script
is fairly small. See section `Utilities in Makefiles' in <CITE>GNU Coding Standards</CITE>, for the list. This
restriction allows users to start out with a fairly small set of
programs and build the rest, avoiding too many interdependencies between
packages.
<P>
Some of these external utilities have a portable subset of features; see
section <A HREF="autoconf.html#SEC119">Limitations of Usual Tools</A>.
<H2><A NAME="SEC111" HREF="autoconf_toc.html#TOC111">Shellology</A></H2>
<P>
There are several families of shells, most prominently the Bourne
family and the C shell family which are deeply incompatible. If you
want to write portable shell scripts, avoid members of the C shell
family.
<P>
Below we describe some of the members of the Bourne shell family.
<DL COMPACT>
<DT>Ash
<DD>
<A NAME="IDX686"></A>
@command{ash} is often used on GNU/Linux and BSD systems as a
light-weight Bourne-compatible shell. Ash 0.2 has some bugs that are
fixed in the 0.3.x series, but portable shell scripts should workaround
them, since version 0.2 is still shipped with many GNU/Linux
distributions.
To be compatible with Ash 0.2:
<UL>
<LI>
don't use <SAMP>`$?'</SAMP> after expanding empty or unset variables:
<PRE>
foo=
false
$foo
echo "Don't use it: $?"
</PRE>
<LI>
don't use command substitution within variable expansion:
<PRE>
cat ${FOO=`bar`}
</PRE>
<LI>
beware that single builtin substitutions are not performed by a sub
shell, hence their effect applies to the current shell! See section <A HREF="autoconf.html#SEC115">Shell Substitutions</A>, item "Command Substitution".
</UL>
<DT>Bash
<DD>
<A NAME="IDX687"></A>
To detect whether you are running @command{bash}, test if
<CODE>BASH_VERSION</CODE> is set. To disable its extensions and require
POSIX compatibility, run <SAMP>`set -o posix'</SAMP>. See section `Bash POSIX Mode' in <CITE>The GNU Bash Reference Manual</CITE>, for
details.
<DT>Bash 2.05 and later
<DD>
<A NAME="IDX688"></A>
Versions 2.05 and later of @command{bash} use a different format for the
output of the @command{set} builtin, designed to make evaluating this
output easier. However, this output is not compatible with earlier
versions of @command{bash} (or with many other shells, probably). So if
you use @command{bash} 2.05 or higher to execute @command{configure},
you'll need to use @command{bash} 2.05 for all other build tasks as well.
<DT>@command{/usr/xpg4/bin/sh on Solaris}
<DD>
<A NAME="IDX689"></A>
The POSIX-compliant Bourne shell on a Solaris system is
@command{/usr/xpg4/bin/sh} and is part of an extra optional package.
There is no extra charge for this package, but it is also not part of a
minimal OS install and therefore some folks may not have it.
<DT>Zsh
<DD>
<A NAME="IDX690"></A>
To detect whether you are running @command{zsh}, test if
<CODE>ZSH_VERSION</CODE> is set. By default @command{zsh} is <EM>not</EM>
compatible with the Bourne shell: you have to run <SAMP>`emulate sh'</SAMP> and
set <CODE>NULLCMD</CODE> to <SAMP>`:'</SAMP>. See section `Compatibility' in <CITE>The Z Shell Manual</CITE>, for details.
Zsh 3.0.8 is the native @command{/bin/sh} on Mac OS X 10.0.3.
</DL>
<P>
The following discussion between Russ Allbery and Robert Lipe is worth
reading:
<P>
Russ Allbery:
<BLOCKQUOTE>
<P>
The GNU assumption that @command{/bin/sh} is the one and only shell
leads to a permanent deadlock. Vendors don't want to break user's
existant shell scripts, and there are some corner cases in the Bourne
shell that are not completely compatible with a POSIX shell. Thus,
vendors who have taken this route will <EM>never</EM> (OK..."never say
never") replace the Bourne shell (as @command{/bin/sh}) with a
POSIX shell.
</BLOCKQUOTE>
<P>
Robert Lipe:
<BLOCKQUOTE>
<P>
This is exactly the problem. While most (at least most System V's) do
have a Bourne shell that accepts shell functions most vendor
@command{/bin/sh} programs are not the POSIX shell.
<P>
So while most modern systems do have a shell _somewhere_ that meets the
POSIX standard, the challenge is to find it.
</BLOCKQUOTE>
<H2><A NAME="SEC112" HREF="autoconf_toc.html#TOC112">Here-Documents</A></H2>
<P>
Don't rely on <SAMP>`\'</SAMP> being preserved just because it has no special
meaning together with the next symbol. in the native @command{/bin/sh}
on OpenBSD 2.7 <SAMP>`\"'</SAMP> expands to <SAMP>`"'</SAMP> in here-documents with
unquoted delimiter. As a general rule, if <SAMP>`\\'</SAMP> expands to <SAMP>`\'</SAMP>
use <SAMP>`\\'</SAMP> to get <SAMP>`\'</SAMP>.
<P>
With OpenBSD 2.7's @command{/bin/sh}
<PRE>
$ <KBD>cat <<EOF
> \" \\
> EOF</KBD>
" \
</PRE>
<P>
and with Bash:
<PRE>
bash-2.04$ <KBD>cat <<EOF
> \" \\
> EOF</KBD>
\" \
</PRE>
<P>
Many older shells (including the Bourne shell) implement here-documents
inefficiently. Users can generally speed things up by using a faster
shell, e.g., by using the command <SAMP>`bash ./configure'</SAMP> rather than
plain <SAMP>`./configure'</SAMP>.
<P>
Some shells can be extremely inefficient when there are a lot of
here-documents inside a single statement. For instance if your
<TT>`configure.ac'</TT> includes something like:
<PRE>
if <cross_compiling>; then
assume this and that
else
check this
check that
check something else
...
on and on forever
...
fi
</PRE>
<P>
A shell parses the whole <CODE>if</CODE>/<CODE>fi</CODE> construct, creating
temporary files for each here document in it. Some shells create links
for such here-documents on every <CODE>fork</CODE>, so that the clean-up code
they had installed correctly removes them. It is creating the links
that the shell can take forever.
<P>
Moving the tests out of the <CODE>if</CODE>/<CODE>fi</CODE>, or creating multiple
<CODE>if</CODE>/<CODE>fi</CODE> constructs, would improve the performance
significantly. Anyway, this kind of construct is not exactly the
typical use of Autoconf. In fact, it's even not recommended, because M4
macros can't look into shell conditionals, so we may fail to expand a
macro when it was expanded before in a conditional path, and the
condition turned out to be false at run-time, and we end up not
executing the macro at all.
<H2><A NAME="SEC113" HREF="autoconf_toc.html#TOC113">File Descriptors</A></H2>
<P>
Some file descriptors shall not be used, since some systems, admittedly
arcane, use them for special purpose:
<PRE>
3 --- some systems may open it to <SAMP>`/dev/tty'</SAMP>.
4 --- used on the Kubota Titan.
</PRE>
<P>
Don't redirect several times the same file descriptor, as you are doomed
to failure under Ultrix.
<PRE>
ULTRIX V4.4 (Rev. 69) System #31: Thu Aug 10 19:42:23 GMT 1995
UWS V4.4 (Rev. 11)
$ <KBD>eval 'echo matter >fullness' >void</KBD>
illegal io
$ <KBD>eval '(echo matter >fullness)' >void</KBD>
illegal io
$ <KBD>(eval '(echo matter >fullness)') >void</KBD>
Ambiguous output redirect.
</PRE>
<P>
In each case the expected result is of course <TT>`fullness'</TT> containing
<SAMP>`matter'</SAMP> and <TT>`void'</TT> being empty.
<P>
Don't try to redirect the standard error of a command substitution: it
must be done <EM>inside</EM> the command substitution: when running
<SAMP>`: `cd /zorglub` 2>/dev/null'</SAMP> expect the error message to
escape, while <SAMP>`: `cd /zorglub 2>/dev/null`'</SAMP> works properly.
<P>
It is worth noting that Zsh (but not Ash nor Bash) makes it possible
in assignments though: <SAMP>`foo=`cd /zorglub` 2>/dev/null'</SAMP>.
<P>
Most shells, if not all (including Bash, Zsh, Ash), output traces on
stderr, even for sub-shells. This might result in undesired content
if you meant to capture the standard-error output of the inner command:
<PRE>
$ <KBD>ash -x -c '(eval "echo foo >&2") 2>stderr'</KBD>
$ <KBD>cat stderr</KBD>
+ eval echo foo >&2
+ echo foo
foo
$ <KBD>bash -x -c '(eval "echo foo >&2") 2>stderr'</KBD>
$ <KBD>cat stderr</KBD>
+ eval 'echo foo >&2'
++ echo foo
foo
$ <KBD>zsh -x -c '(eval "echo foo >&2") 2>stderr'</KBD>
<I># Traces on startup files deleted here.</I>
$ <KBD>cat stderr</KBD>
+zsh:1> eval echo foo >&2
+zsh:1> echo foo
foo
</PRE>
<P>
You'll appreciate the various levels of detail...
<P>
One workaround is to grep out uninteresting lines, hoping not to remove
good ones...
<P>
Don't try to move/delete open files, such as in <SAMP>`exec >foo; mv foo
bar'</SAMP>, see See section <A HREF="autoconf.html#SEC118">Limitations of Shell Builtins</A>, @command{mv} for more details.
<H2><A NAME="SEC114" HREF="autoconf_toc.html#TOC114">File System Conventions</A></H2>
<P>
While @command{autoconf} and friends will usually be run on some Unix
variety, it can and will be used on other systems, most notably DOS
variants. This impacts several assumptions regarding file and
path names.
<P>
For example, the following code:
<PRE>
case $foo_dir in
/*) # Absolute
;;
*)
foo_dir=$dots$foo_dir ;;
esac
</PRE>
<P>
will fail to properly detect absolute paths on those systems, because
they can use a drivespec, and will usually use a backslash as directory
separator. The canonical way to check for absolute paths is:
<PRE>
case $foo_dir in
[\\/]* | ?:[\\/]* ) # Absolute
;;
*)
foo_dir=$dots$foo_dir ;;
esac
</PRE>
<P>
Make sure you quote the brackets if appropriate and keep the backslash as
first character (see section <A HREF="autoconf.html#SEC118">Limitations of Shell Builtins</A>).
<P>
Also, because the colon is used as part of a drivespec, these systems don't
use it as path separator. When creating or accessing paths, use the
<CODE>PATH_SEPARATOR</CODE> output variable instead. @command{configure} sets this
to the appropriate value (<SAMP>`:'</SAMP> or <SAMP>`;'</SAMP>) when it starts up.
<P>
File names need extra care as well. While DOS-based environments
that are Unixy enough to run @command{autoconf} (such as DJGPP) will
usually be able to handle long file names properly, there are still
limitations that can seriously break packages. Several of these issues
can be easily detected by the
@href{ftp://ftp.gnu.org/gnu/non-gnu/doschk/doschk-1.1.tar.gz, doschk}
package.
<P>
A short overview follows; problems are marked with SFN/LFN to
indicate where they apply: SFN means the issues are only relevant to
plain DOS, not to DOS boxes under Windows, while LFN
identifies problems that exist even under Windows.
<DL COMPACT>
<DT>No multiple dots (SFN)
<DD>
DOS cannot handle multiple dots in filenames. This is an especially
important thing to remember when building a portable configure script,
as @command{autoconf} uses a .in suffix for template files.
This is perfectly OK on Unices:
<PRE>
AC_CONFIG_HEADER(config.h)
AC_CONFIG_FILES([source.c foo.bar])
AC_OUTPUT
</PRE>
but it causes problems on DOS, as it requires <SAMP>`config.h.in'</SAMP>,
<SAMP>`source.c.in'</SAMP> and <SAMP>`foo.bar.in'</SAMP>. To make your package more portable
to DOS-based environments, you should use this instead:
<PRE>
AC_CONFIG_HEADER(config.h:config.hin)
AC_CONFIG_FILES([source.c:source.cin foo.bar:foobar.in])
AC_OUTPUT
</PRE>
<DT>No leading dot (SFN)
<DD>
DOS cannot handle filenames that start with a dot. This is usually
not a very important issue for @command{autoconf}.
<DT>Case insensitivity (LFN)
<DD>
DOS is case insensitive, so you cannot, for example, have both a
file called <SAMP>`INSTALL'</SAMP> and a directory called <SAMP>`install'</SAMP>. This
also affects @command{make}; if there's a file called <SAMP>`INSTALL'</SAMP> in
the directory, @command{make install} will do nothing (unless the
<SAMP>`install'</SAMP> target is marked as PHONY).
<DT>The 8+3 limit (SFN)
<DD>
Because the DOS file system only stores the first 8 characters of
the filename and the first 3 of the extension, those must be unique.
That means that <TT>`foobar-part1.c'</TT>, <TT>`foobar-part2.c'</TT> and
<TT>`foobar-prettybird.c'</TT> all resolve to the same filename
(<TT>`FOOBAR-P.C'</TT>). The same goes for <TT>`foo.bar'</TT> and
<TT>`foo.bartender'</TT>.
Note: This is not usually a problem under Windows, as it uses numeric
tails in the short version of filenames to make them unique. However, a
registry setting can turn this behaviour off. While this makes it
possible to share file trees containing long file names between SFN
and LFN environments, it also means the above problem applies there
as well.
<DT>Invalid characters
<DD>
Some characters are invalid in DOS filenames, and should therefore
be avoided. In a LFN environment, these are <SAMP>`/'</SAMP>, <SAMP>`\'</SAMP>,
<SAMP>`?'</SAMP>, <SAMP>`*'</SAMP>, <SAMP>`:'</SAMP>, <SAMP>`<'</SAMP>, <SAMP>`>'</SAMP>, <SAMP>`|'</SAMP> and <SAMP>`"'</SAMP>.
In a SFN environment, other characters are also invalid. These
include <SAMP>`+'</SAMP>, <SAMP>`,'</SAMP>, <SAMP>`['</SAMP> and <SAMP>`]'</SAMP>.
</DL>
<H2><A NAME="SEC115" HREF="autoconf_toc.html#TOC115">Shell Substitutions</A></H2>
<P>
Contrary to a persistent urban legend, the Bourne shell does not
systematically split variables and backquoted expressions, in particular
on the right-hand side of assignments and in the argument of <CODE>case</CODE>.
For instance, the following code:
<PRE>
case "$given_srcdir" in
.) top_srcdir="`echo "$dots" | sed 's,/$,,'`"
*) top_srcdir="$dots$given_srcdir" ;;
esac
</PRE>
<P>
is more readable when written as:
<PRE>
case $given_srcdir in
.) top_srcdir=`echo "$dots" | sed 's,/$,,'`
*) top_srcdir=$dots$given_srcdir ;;
esac
</PRE>
<P>
and in fact it is even <EM>more</EM> portable: in the first case of the
first attempt, the computation of <CODE>top_srcdir</CODE> is not portable,
since not all shells properly understand <CODE>"`..."..."...`"</CODE>.
Worse yet, not all shells understand <CODE>"`...\"...\"...`"</CODE>
the same way. There is just no portable way to use double-quoted
strings inside double-quoted backquoted expressions (pfew!).
<DL COMPACT>
<DT><CODE>$@</CODE>
<DD>
<A NAME="IDX691"></A>
One of the most famous shell-portability issues is related to
<SAMP>`"$@"'</SAMP>: when there are no positional arguments, it is supposed to
be equivalent to nothing. But some shells, for instance under Digital
Unix 4.0 and 5.0, will then replace it with an empty argument. To be
portable, use <SAMP>`${1+"$@"}'</SAMP>.
<DT><CODE>${<VAR>var</VAR>:-<VAR>value</VAR>}</CODE>
<DD>
<A NAME="IDX692"></A>
Old BSD shells, including the Ultrix <CODE>sh</CODE>, don't accept the
colon for any shell substitution, and complain and die.
<DT><CODE>${<VAR>var</VAR>=<VAR>literal</VAR>}</CODE>
<DD>
<A NAME="IDX693"></A>
Be sure to quote:
<PRE>
: ${var='Some words'}
</PRE>
otherwise some shells, such as on Digital Unix V 5.0, will die because
of a "bad substitution".
Solaris' @command{/bin/sh} has a frightening bug in its interpretation
of this. Imagine you need set a variable to a string containing
<SAMP>`}'</SAMP>. This <SAMP>`}'</SAMP> character confuses Solaris' @command{/bin/sh}
when the affected variable was already set. This bug can be exercised
by running:
<PRE>
$ <KBD>unset foo</KBD>
$ <KBD>foo=${foo='}'}</KBD>
$ <KBD>echo $foo</KBD>
}
$ <KBD>foo=${foo='}' # no error; this hints to what the bug is</KBD>
$ <KBD>echo $foo</KBD>
}
$ <KBD>foo=${foo='}'}</KBD>
$ <KBD>echo $foo</KBD>
}}
^ ugh!
</PRE>
It seems that <SAMP>`}'</SAMP> is interpreted as matching <SAMP>`${'</SAMP>, even
though it is enclosed in single quotes. The problem doesn't happen
using double quotes.
<DT><CODE>${<VAR>var</VAR>=<VAR>expanded-value</VAR>}</CODE>
<DD>
<A NAME="IDX694"></A>
On Ultrix,
running
<PRE>
default="yu,yaa"
: ${var="$default"}
</PRE>
will set <VAR>var</VAR> to <SAMP>`M-yM-uM-,M-yM-aM-a'</SAMP>, i.e., the 8th bit of
each char will be set. You won't observe the phenomenon using a simple
<SAMP>`echo $var'</SAMP> since apparently the shell resets the 8th bit when it
expands $var. Here are two means to make this shell confess its sins:
<PRE>
$ <KBD>cat -v <<EOF
$var
EOF</KBD>
</PRE>
and
<PRE>
$ <KBD>set | grep '^var=' | cat -v</KBD>
</PRE>
One classic incarnation of this bug is:
<PRE>
default="a b c"
: ${list="$default"}
for c in $list; do
echo $c
done
</PRE>
You'll get <SAMP>`a b c'</SAMP> on a single line. Why? Because there are no
spaces in <SAMP>`$list'</SAMP>: there are <SAMP>`M- '</SAMP>, i.e., spaces with the 8th
bit set, hence no IFS splitting is performed!!!
One piece of good news is that Ultrix works fine with <SAMP>`:
${list=$default}'</SAMP>; i.e., if you <EM>don't</EM> quote. The bad news is
then that QNX 4.25 then sets <VAR>list</VAR> to the <EM>last</EM> item of
<VAR>default</VAR>!
The portable way out consists in using a double assignment, to switch
the 8th bit twice on Ultrix:
<PRE>
list=${list="$default"}
</PRE>
...but beware of the <SAMP>`}'</SAMP> bug from Solaris (see above). For safety,
use:
<PRE>
test "${var+set}" = set || var=<VAR>{value}</VAR>
</PRE>
<DT><CODE>`<VAR>commands</VAR>`</CODE>
<DD>
<A NAME="IDX695"></A>
<A NAME="IDX696"></A>
While in general it makes no sense, do not substitute a single builtin
with side effects as Ash 0.2, trying to optimize, does not fork a
sub-shell to perform the command.
For instance, if you wanted to check that @command{cd} is silent, do not
use <SAMP>`test -z "`cd /`"'</SAMP> because the following can happen:
<PRE>
$ <KBD>pwd</KBD>
/tmp
$ <KBD>test -n "`cd /`" && pwd</KBD>
/
</PRE>
The result of <SAMP>`foo=`exit 1`'</SAMP> is left as an exercise to the reader.
<DT><CODE>$(<VAR>commands</VAR>)</CODE>
<DD>
<A NAME="IDX697"></A>
This construct is meant to replace <SAMP>``<VAR>commands</VAR>`'</SAMP>; they can be
nested while this is impossible to do portably with back quotes.
Unfortunately it is not yet widely supported. Most notably, even recent
releases of Solaris don't support it:
<PRE>
$ <KBD>showrev -c /bin/sh | grep version</KBD>
Command version: SunOS 5.8 Generic 109324-02 February 2001
$ <KBD>echo $(echo blah)</KBD>
syntax error: `(' unexpected
</PRE>
nor does IRIX 6.5's Bourne shell:
<PRE>
$ <KBD>uname -a</KBD>
IRIX firebird-image 6.5 07151432 IP22
$ <KBD>echo $(echo blah)</KBD>
$(echo blah)
</PRE>
</DL>
<H2><A NAME="SEC116" HREF="autoconf_toc.html#TOC116">Assignments</A></H2>
<P>
When setting several variables in a row, be aware that the order of the
evaluation is undefined. For instance <SAMP>`foo=1 foo=2; echo $foo'</SAMP>
gives <SAMP>`1'</SAMP> with sh on Solaris, but <SAMP>`2'</SAMP> with Bash. You must use
<SAMP>`;'</SAMP> to enforce the order: <SAMP>`foo=1; foo=2; echo $foo'</SAMP>.
<P>
Don't rely on the exit status of an assignment: Ash 0.2 does not change
the status and propagates that of the last statement:
<PRE>
$ <KBD>false || foo=bar; echo $?</KBD>
1
$ <KBD>false || foo=`:`; echo $?</KBD>
0
</PRE>
<P>
and to make things even worse, QNX 4.25 just sets the exit status
to 0 in any case:
<PRE>
$ <KBD>foo=`exit 1`; echo $?</KBD>
0
</PRE>
<P>
To assign default values, follow this algorithm:
<OL>
<LI>
If the default value is a literal and does not contain any closing
brace, use:
<PRE>
: ${var='my literal'}
</PRE>
<LI>
If the default value contains no closing brace, has to be expanded, and
the variable being initialized will never be IFS-split (i.e., it's not a
list), then use:
<PRE>
: ${var="$default"}
</PRE>
<LI>
If the default value contains no closing brace, has to be expanded, and
the variable being initialized will be IFS-split (i.e., it's a list),
then use:
<PRE>
var=${var="$default"}
</PRE>
<LI>
If the default value contains a closing brace, then use:
<PRE>
test "${var+set}" = set || var='${indirection}'
</PRE>
</OL>
<P>
In most cases <SAMP>`var=${var="$default"}'</SAMP> is fine, but in case of
doubt, just use the latter. See section <A HREF="autoconf.html#SEC115">Shell Substitutions</A>, items
<SAMP>`${<VAR>var</VAR>:-<VAR>value</VAR>}'</SAMP> and <SAMP>`${<VAR>var</VAR>=<VAR>value</VAR>}'</SAMP>
for the rationale.
<H2><A NAME="SEC117" HREF="autoconf_toc.html#TOC117">Special Shell Variables</A></H2>
<P>
Some shell variables should not be used, since they can have a deep
influence on the behavior of the shell. In order to recover a sane
behavior from the shell, some variables should be unset, but
@command{unset} is not portable (see section <A HREF="autoconf.html#SEC118">Limitations of Shell Builtins</A>) and a
fallback value is needed. We list these values below.
<DL COMPACT>
<DT><CODE>CDPATH</CODE>
<DD>
<A NAME="IDX698"></A>
When this variable is set <CODE>cd</CODE> is verbose, so idioms such as
<SAMP>`abs=`cd $rel && pwd`'</SAMP> break because <CODE>abs</CODE> receives the path
twice.
Setting <CODE>CDPATH</CODE> to the empty value is not enough for most shells.
A simple path separator is enough except for <CODE>zsh</CODE>, which prefers a
leading dot:
<PRE>
zsh-3.1.6$ <KBD>mkdir foo && (CDPATH=: cd foo)</KBD>
/tmp/foo
zsh-3.1.6$ <KBD>(CDPATH=:. cd foo)</KBD>
/tmp/foo
zsh-3.1.6$ <KBD>(CDPATH=.: cd foo)</KBD>
zsh-3.1.6$
</PRE>
(of course we could just @command{unset} <CODE>CDPATH</CODE>, since it also
behaves properly if set to the empty string).
Life wouldn't be so much fun if @command{bash} and @command{zsh} had the
same behavior:
<PRE>
bash-2.02$ <KBD>mkdir foo && (CDPATH=: cd foo)</KBD>
bash-2.02$ <KBD>(CDPATH=:. cd foo)</KBD>
bash-2.02$ <KBD>(CDPATH=.: cd foo)</KBD>
/tmp/foo
</PRE>
Of course, even better style would be to use <CODE>PATH_SEPARATOR</CODE> instead
of a <SAMP>`:'</SAMP>.
Therefore, a portable solution to neutralize <CODE>CDPATH</CODE> is
<PRE>
CDPATH=${ZSH_VERSION+.}$PATH_SEPARATOR
</PRE>
Note that since @command{zsh} supports @command{unset}, you may unset
<CODE>CDPATH</CODE> using <CODE>PATH_SEPARATOR</CODE> as a fallback, see
section <A HREF="autoconf.html#SEC118">Limitations of Shell Builtins</A>.
<DT><CODE>IFS</CODE>
<DD>
<A NAME="IDX699"></A>
Don't set the first character of <CODE>IFS</CODE> to backslash. Indeed,
Bourne shells use the first character (backslash) when joining the
components in <SAMP>`"$@"'</SAMP> and some shells then re-interpret (!) the
backslash escapes, so you can end up with backspace and other strange
characters.
<DT><CODE>LANG</CODE>
<DD>
<DT><CODE>LC_ALL</CODE>
<DD>
<DT><CODE>LC_COLLATE</CODE>
<DD>
<DT><CODE>LC_CTYPE</CODE>
<DD>
<DT><CODE>LC_MESSAGES</CODE>
<DD>
<DT><CODE>LC_NUMERIC</CODE>
<DD>
<DT><CODE>LC_TIME</CODE>
<DD>
<A NAME="IDX700"></A>
<A NAME="IDX701"></A>
<A NAME="IDX702"></A>
<A NAME="IDX703"></A>
<A NAME="IDX704"></A>
<A NAME="IDX705"></A>
<A NAME="IDX706"></A>
Autoconf-generated scripts normally set all these variables to
<SAMP>`C'</SAMP> because so much configuration code assumes the C locale and
POSIX requires that @env{LC_ALL} be set to <SAMP>`C'</SAMP> if the C
locale is desired. However, some older, nonstandard systems (notably
SCO) break if @env{LC_ALL} is set to <SAMP>`C'</SAMP>, so when running on
these systems Autoconf-generated scripts first try to unset the
variables instead.
<DT><CODE>LANGUAGE</CODE>
<DD>
<A NAME="IDX707"></A>
@env{LANGUAGE} is not specified by POSIX, but it is a GNU
extension that overrides @env{LC_ALL} in some cases, so
Autoconf-generated scripts set it too.
<DT><CODE>LINENO</CODE>
<DD>
<A NAME="IDX708"></A>
Most modern shells provide the current line number in <CODE>LINENO</CODE>.
Its value is the line number of the beginning of the current command.
Autoconf attempts to execute @command{configure} with a modern shell.
If no such shell is available, it attempts to implement <CODE>LINENO</CODE>
with a Sed prepass that replaces the each instance of the string
<CODE>$LINENO</CODE> (not followed by an alphanumeric character) with the
line's number.
You should not rely on <CODE>LINENO</CODE> within @command{eval}, as the
behavior differs in practice. Also, the possibility of the Sed
prepass means that you should not rely on <CODE>$LINENO</CODE> when quoted,
when in here-documents, or when in long commands that cross line
boundaries. Subshells should be OK, though. In the following
example, lines 1, 6, and 9 are portable, but the other instances of
<CODE>LINENO</CODE> are not:
<PRE>
$ <KBD>cat lineno</KBD>
echo 1. $LINENO
cat <<EOF
3. $LINENO
4. $LINENO
EOF
( echo 6. $LINENO )
eval 'echo 7. $LINENO'
echo 8. '$LINENO'
echo 9. $LINENO '
10.' $LINENO
$ <KBD>bash-2.05 lineno</KBD>
1. 1
3. 2
4. 2
6. 6
7. 1
8. $LINENO
9. 9
10. 9
$ <KBD>zsh-3.0.6 lineno</KBD>
1. 1
3. 2
4. 2
6. 6
7. 7
8. $LINENO
9. 9
10. 9
$ <KBD>pdksh-5.2.14 lineno</KBD>
1. 1
3. 2
4. 2
6. 6
7. 0
8. $LINENO
9. 9
10. 9
$ <KBD>sed '=' <lineno |</KBD>
> <KBD> sed '</KBD>
> <KBD> N</KBD>
> <KBD> s,$,-,</KBD>
> <KBD> : loop</KBD>
> <KBD> s,^\([0-9]*\)\(.*\)[$]LINENO\([^a-zA-Z0-9_]\),\1\2\1\3,</KBD>
> <KBD> t loop</KBD>
> <KBD> s,-$,,</KBD>
> <KBD> s,^[0-9]*\n,,</KBD>
> <KBD> ' |</KBD>
> <KBD> sh</KBD>
1. 1
3. 3
4. 4
6. 6
7. 7
8. 8
9. 9
10. 10
</PRE>
<DT><CODE>NULLCMD</CODE>
<DD>
<A NAME="IDX709"></A>
When executing the command <SAMP>`>foo'</SAMP>, @command{zsh} executes
<SAMP>`$NULLCMD >foo'</SAMP>. The Bourne shell considers <CODE>NULLCMD</CODE> is
<SAMP>`:'</SAMP>, while @command{zsh}, even in Bourne shell compatibility mode,
sets <CODE>NULLCMD</CODE> to <SAMP>`cat'</SAMP>. If you forgot to set <CODE>NULLCMD</CODE>,
your script might be suspended waiting for data on its standard input.
<DT><CODE>status</CODE>
<DD>
<A NAME="IDX710"></A>
This variable is an alias to <SAMP>`$?'</SAMP> for <CODE>zsh</CODE> (at least 3.1.6),
hence read-only. Do not use it.
<DT><CODE>PATH_SEPARATOR</CODE>
<DD>
<A NAME="IDX711"></A>
If it is not set, @command{configure} will detect the appropriate path
separator for the build system and set the <CODE>PATH_SEPARATOR</CODE> output
variable accordingly.
On DJGPP systems, the <CODE>PATH_SEPARATOR</CODE> environment variable can be
set to either <SAMP>`:'</SAMP> or <SAMP>`;'</SAMP> to control the path separator
@command{bash} uses to set up certain environment variables (such as
<CODE>PATH</CODE>). Since this only works inside @command{bash}, you want
@command{configure} to detect the regular DOS path separator
(<SAMP>`;'</SAMP>), so it can be safely substituted in files that may not support
<SAMP>`;'</SAMP> as path separator. So it is recommended to either unset this
variable or set it to <SAMP>`;'</SAMP>.
<DT><CODE>RANDOM</CODE>
<DD>
<A NAME="IDX712"></A>
Many shells provide <CODE>RANDOM</CODE>, a variable that returns a different
integer when used. Most of the time, its value does not change when it
is not used, but on IRIX 6.5 the value changes all the time. This
can be observed by using @command{set}.
</DL>
<H2><A NAME="SEC118" HREF="autoconf_toc.html#TOC118">Limitations of Shell Builtins</A></H2>
<P>
No, no, we are serious: some shells do have limitations! :)
<P>
You should always keep in mind that any built-in or command may support
options, and therefore have a very different behavior with arguments
starting with a dash. For instance, the innocent <SAMP>`echo "$word"'</SAMP>
can give unexpected results when <CODE>word</CODE> starts with a dash. It is
often possible to avoid this problem using <SAMP>`echo "x$word"'</SAMP>, taking
the <SAMP>`x'</SAMP> into account later in the pipe.
<DL COMPACT>
<DT>@command{.}
<DD>
<A NAME="IDX713"></A>
Use @command{.} only with regular files (use <SAMP>`test -f'</SAMP>). Bash
2.03, for instance, chokes on <SAMP>`. /dev/null'</SAMP>. Also, remember that
@command{.} uses @env{PATH} if its argument contains no slashes, so if
you want to use @command{.} on a file <TT>`foo'</TT> in the current
directory, you must use <SAMP>`. ./foo'</SAMP>.
<DT>@command{!}
<DD>
<A NAME="IDX714"></A>
You can't use @command{!}, you'll have to rewrite your code.
<DT>@command{break}
<DD>
<A NAME="IDX715"></A>
The use of <SAMP>`break 2'</SAMP>, etcetera, is safe.
<DT>@command{case}
<DD>
<A NAME="IDX716"></A>
You don't need to quote the argument; no splitting is performed.
You don't need the final <SAMP>`;;'</SAMP>, but you should use it.
Because of a bug in its <CODE>fnmatch</CODE>, @command{bash} fails to properly
handle backslashes in character classes:
<PRE>
bash-2.02$ <KBD>case /tmp in [/\\]*) echo OK;; esac</KBD>
bash-2.02$
</PRE>
This is extremely unfortunate, since you are likely to use this code to
handle UNIX or MS-DOS absolute paths. To work around this
bug, always put the backslash first:
<PRE>
bash-2.02$ <KBD>case '\TMP' in [\\/]*) echo OK;; esac</KBD>
OK
bash-2.02$ <KBD>case /tmp in [\\/]*) echo OK;; esac</KBD>
OK
</PRE>
Some shells, such as Ash 0.3.8, are confused by empty
<CODE>case</CODE>/<CODE>esac</CODE>:
<PRE>
ash-0.3.8 $ <KBD>case foo in esac;</KBD>
error-->Syntax error: ";" unexpected (expecting ")")
</PRE>
Many shells still do not support parenthesized cases, which is a pity
for those of us using tools that rely on balanced parentheses. For
instance, Solaris 2.8's Bourne shell:
<PRE>
$ <KBD>case foo in (foo) echo foo;; esac</KBD>
error-->syntax error: `(' unexpected
</PRE>
<DT>@command{echo}
<DD>
<A NAME="IDX717"></A>
The simple <CODE>echo</CODE> is probably the most surprising source of
portability troubles. It is not possible to use <SAMP>`echo'</SAMP> portably
unless both options and escape sequences are omitted. New applications
which are not aiming at portability should use <SAMP>`printf'</SAMP> instead of
<SAMP>`echo'</SAMP>.
Don't expect any option. See section <A HREF="autoconf.html#SEC23">Preset Output Variables</A>, <CODE>ECHO_N</CODE>
etc. for a means to simulate @option{-c}.
Do not use backslashes in the arguments, as there is no consensus on
their handling. On <SAMP>`echo '\n' | wc -l'</SAMP>, the @command{sh} of
Digital Unix 4.0, MIPS RISC/OS 4.52, answer 2, but the Solaris'
@command{sh}, Bash and Zsh (in @command{sh} emulation mode) report 1.
Please note that the problem is truly @command{echo}: all the shells
understand <SAMP>`'\n''</SAMP> as the string composed of a backslash and an
<SAMP>`n'</SAMP>.
Because of these problems, do not pass a string containing arbitrary
characters to @command{echo}. For example, <SAMP>`echo "$foo"'</SAMP> is safe
if you know that <VAR>foo</VAR>'s value cannot contain backslashes and cannot
start with <SAMP>`-'</SAMP>, but otherwise you should use a here-document like
this:
<PRE>
cat <<EOF
$foo
EOF
</PRE>
<DT>@command{exit}
<DD>
<A NAME="IDX718"></A>
The default value of @command{exit} is supposed to be <CODE>$?</CODE>;
unfortunately, some shells, such as the DJGPP port of Bash 2.04, just
perform <SAMP>`exit 0'</SAMP>.
<PRE>
bash-2.04$ <KBD>foo=`exit 1` || echo fail</KBD>
fail
bash-2.04$ <KBD>foo=`(exit 1)` || echo fail</KBD>
fail
bash-2.04$ <KBD>foo=`(exit 1); exit` || echo fail</KBD>
bash-2.04$
</PRE>
Using <SAMP>`exit $?'</SAMP> restores the expected behavior.
Some shell scripts, such as those generated by @command{autoconf}, use a
trap to clean up before exiting. If the last shell command exited with
nonzero status, the trap also exits with nonzero status so that the
invoker can tell that an error occurred.
Unfortunately, in some shells, such as Solaris 8 @command{sh}, an exit
trap ignores the <CODE>exit</CODE> command's status. In these shells, a trap
cannot determine whether it was invoked by plain <CODE>exit</CODE> or by
<CODE>exit 1</CODE>. Instead of calling <CODE>exit</CODE> directly, use the
<CODE>AC_MSG_ERROR</CODE> macro that has a workaround for this problem.
<DT>@command{export}
<DD>
<A NAME="IDX719"></A>
The builtin @command{export} dubs <EM>environment variable</EM> a shell
variable. Each update of exported variables corresponds to an update of
the environment variables. Conversely, each environment variable
received by the shell when it is launched should be imported as a shell
variable marked as exported.
Alas, many shells, such as Solaris 2.5, IRIX 6.3, IRIX 5.2, AIX 4.1.5
and DU 4.0, forget to @command{export} the environment variables they
receive. As a result, two variables are coexisting: the environment
variable and the shell variable. The following code demonstrates this
failure:
<PRE>
#! /bin/sh
echo $FOO
FOO=bar
echo $FOO
exec /bin/sh $0
</PRE>
when run with <SAMP>`FOO=foo'</SAMP> in the environment, these shells will print
alternately <SAMP>`foo'</SAMP> and <SAMP>`bar'</SAMP>, although it should only print
<SAMP>`foo'</SAMP> and then a sequence of <SAMP>`bar'</SAMP>s.
Therefore you should @command{export} again each environment variable
that you update.
<DT>@command{false}
<DD>
<A NAME="IDX720"></A>
Don't expect @command{false} to exit with status 1: in the native Bourne
shell of Solaris 8, it exits with status 255.
<DT>@command{for}
<DD>
<A NAME="IDX721"></A>
To loop over positional arguments, use:
<PRE>
for arg
do
echo "$arg"
done
</PRE>
You may <EM>not</EM> leave the <CODE>do</CODE> on the same line as <CODE>for</CODE>,
since some shells improperly grok:
<PRE>
for arg; do
echo "$arg"
done
</PRE>
If you want to explicitly refer to the positional arguments, given the
<SAMP>`$@'</SAMP> bug (see section <A HREF="autoconf.html#SEC115">Shell Substitutions</A>), use:
<PRE>
for arg in ${1+"$@"}; do
echo "$arg"
done
</PRE>
<DT>@command{if}
<DD>
<A NAME="IDX722"></A>
Using <SAMP>`!'</SAMP> is not portable. Instead of:
<PRE>
if ! cmp -s file file.new; then
mv file.new file
fi
</PRE>
use:
<PRE>
if cmp -s file file.new; then :; else
mv file.new file
fi
</PRE>
There are shells that do not reset the exit status from an @command{if}:
<PRE>
$ <KBD>if (exit 42); then true; fi; echo $?</KBD>
42
</PRE>
whereas a proper shell should have printed <SAMP>`0'</SAMP>. This is especially
bad in Makefiles since it produces false failures. This is why properly
written Makefiles, such as Automake's, have such hairy constructs:
<PRE>
if test -f "$file"; then
install "$file" "$dest"
else
:
fi
</PRE>
<DT>@command{set}
<DD>
<A NAME="IDX723"></A>
This builtin faces the usual problem with arguments starting with a
dash. Modern shells such as Bash or Zsh understand @option{--} to specify
the end of the options (any argument after @option{--} is a parameters,
even <SAMP>`-x'</SAMP> for instance), but most shells simply stop the option
processing as soon as a non-option argument is found. Therefore, use
<SAMP>`dummy'</SAMP> or simply <SAMP>`x'</SAMP> to end the option processing, and use
@command{shift} to pop it out:
<PRE>
set x $my_list; shift
</PRE>
<DT>@command{shift}
<DD>
<A NAME="IDX724"></A>
Not only is @command{shift}ing a bad idea when there is nothing left to
shift, but in addition it is not portable: the shell of MIPS
RISC/OS 4.52 refuses to do it.
<DT>@command{source}
<DD>
<A NAME="IDX725"></A>
This command is not portable, as POSIX does not require it; use
@command{.} instead.
<DT>@command{test}
<DD>
<A NAME="IDX726"></A>
The <CODE>test</CODE> program is the way to perform many file and string
tests. It is often invoked by the alternate name <SAMP>`['</SAMP>, but using
that name in Autoconf code is asking for trouble since it is an M4 quote
character.
If you need to make multiple checks using <CODE>test</CODE>, combine them with
the shell operators <SAMP>`&&'</SAMP> and <SAMP>`||'</SAMP> instead of using the
<CODE>test</CODE> operators @option{-a} and @option{-o}. On System V, the
precedence of @option{-a} and @option{-o} is wrong relative to the unary
operators; consequently, POSIX does not specify them, so using them
is nonportable. If you combine <SAMP>`&&'</SAMP> and <SAMP>`||'</SAMP> in the same
statement, keep in mind that they have equal precedence.
You may use <SAMP>`!'</SAMP> with @command{test}, but not with @command{if}:
<SAMP>`test ! -r foo || exit 1'</SAMP>.
<DT>@command{test (files)}
<DD>
To enable @command{configure} scripts to support cross-compilation, they
shouldn't do anything that tests features of the build system instead of
the host system. But occasionally you may find it necessary to check
whether some arbitrary file exists. To do so, use <SAMP>`test -f'</SAMP> or
<SAMP>`test -r'</SAMP>. Do not use <SAMP>`test -x'</SAMP>, because 4.3BSD does not
have it. Do not use <SAMP>`test -e'</SAMP> either, because Solaris 2.5 does not
have it.
<DT>@command{test (strings)}
<DD>
Avoid <SAMP>`test "<VAR>string</VAR>"'</SAMP>, in particular if <VAR>string</VAR> might
start with a dash, since <CODE>test</CODE> might interpret its argument as an
option (e.g., <SAMP>`<VAR>string</VAR> = "-n"'</SAMP>).
Contrary to a common belief, <SAMP>`test -n <VAR>string</VAR>'</SAMP> and <SAMP>`test
-z <VAR>string</VAR>'</SAMP> <STRONG>are</STRONG> portable, nevertheless many shells (such
as Solaris 2.5, AIX 3.2, UNICOS 10.0.0.6, Digital Unix 4 etc.) have
bizarre precedence and may be confused if <VAR>string</VAR> looks like an
operator:
<PRE>
$ <KBD>test -n =</KBD>
test: argument expected
</PRE>
If there are risks, use <SAMP>`test "x<VAR>string</VAR>" = x'</SAMP> or <SAMP>`test
"x<VAR>string</VAR>" != x'</SAMP> instead.
It is frequent to find variations of the following idiom:
<PRE>
test -n "`echo $ac_feature | sed 's/[-a-zA-Z0-9_]//g'`" &&
<VAR>action</VAR>
</PRE>
to take an action when a token matches a given pattern. Such constructs
should always be avoided by using:
<PRE>
echo "$ac_feature" | grep '[^-a-zA-Z0-9_]' >/dev/null 2>&1 &&
<VAR>action</VAR>
</PRE>
Use <CODE>case</CODE> where possible since it is faster, being a shell builtin:
<PRE>
case $ac_feature in
*[!-a-zA-Z0-9_]*) <VAR>action</VAR>;;
esac
</PRE>
Alas, negated character classes are probably not portable, although no
shell is known to not support the POSIX.2 syntax <SAMP>`[!...]'</SAMP>
(when in interactive mode, @command{zsh} is confused by the
<SAMP>`[!...]'</SAMP> syntax and looks for an event in its history because of
<SAMP>`!'</SAMP>). Many shells do not support the alternative syntax
<SAMP>`[^...]'</SAMP> (Solaris, Digital Unix, etc.).
One solution can be:
<PRE>
expr "$ac_feature" : '.*[^-a-zA-Z0-9_]' >/dev/null &&
<VAR>action</VAR>
</PRE>
or better yet
<PRE>
expr "x$ac_feature" : '.*[^-a-zA-Z0-9_]' >/dev/null &&
<VAR>action</VAR>
</PRE>
<SAMP>`expr "X<VAR>foo</VAR>" : "X<VAR>bar</VAR>"'</SAMP> is more robust than <SAMP>`echo
"X<VAR>foo</VAR>" | grep "^X<VAR>bar</VAR>"'</SAMP>, because it avoids problems when
<SAMP>`<VAR>foo</VAR>'</SAMP> contains backslashes.
<DT>@command{trap}
<DD>
<A NAME="IDX727"></A>
It is safe to trap at least the signals 1, 2, 13 and 15. You can also
trap 0, i.e., have the @command{trap} run when the script ends (either via an
explicit @command{exit}, or the end of the script).
Although POSIX is not absolutely clear on this point, it is widely
admitted that when entering the trap <SAMP>`$?'</SAMP> should be set to the exit
status of the last command run before the trap. The ambiguity can be
summarized as: "when the trap is launched by an @command{exit}, what is
the <EM>last</EM> command run: that before @command{exit}, or
@command{exit} itself?"
Bash considers @command{exit} to be the last command, while Zsh and
Solaris 8 @command{sh} consider that when the trap is run it is
<EM>still</EM> in the @command{exit}, hence it is the previous exit status
that the trap receives:
<PRE>
$ <KBD>cat trap.sh</KBD>
trap 'echo $?' 0
(exit 42); exit 0
$ <KBD>zsh trap.sh</KBD>
42
$ <KBD>bash trap.sh</KBD>
0
</PRE>
The portable solution is then simple: when you want to <SAMP>`exit 42'</SAMP>,
run <SAMP>`(exit 42); exit 42'</SAMP>, the first @command{exit} being used to
set the exit status to 42 for Zsh, and the second to trigger the trap
and pass 42 as exit status for Bash.
The shell in FreeBSD 4.0 has the following bug: <SAMP>`$?'</SAMP> is reset to 0
by empty lines if the code is inside @command{trap}.
<PRE>
$ <KBD>trap 'false</KBD>
echo $?' 0
$ <KBD>exit</KBD>
0
</PRE>
Fortunately, this bug only affects @command{trap}.
<DT>@command{true}
<DD>
<A NAME="IDX728"></A>
<A NAME="IDX729"></A>
Don't worry: as far as we know @command{true} is portable.
Nevertheless, it's not always a builtin (e.g., Bash 1.x), and the
portable shell community tends to prefer using @command{:}. This has a
funny side effect: when asked whether @command{false} is more portable
than @command{true} Alexandre Oliva answered:
<BLOCKQUOTE>
<P>
In a sense, yes, because if it doesn't exist, the shell will produce an
exit status of failure, which is correct for @command{false}, but not
for @command{true}.
</BLOCKQUOTE>
<DT>@command{unset}
<DD>
<A NAME="IDX730"></A>
You cannot assume the support of @command{unset}, nevertheless, because
it is extremely useful to disable embarrassing variables such as
<CODE>CDPATH</CODE>, you can test for its existence and use
it <EM>provided</EM> you give a neutralizing value when @command{unset} is
not supported:
<PRE>
if (unset FOO) >/dev/null 2>&1; then
unset=unset
else
unset=false
fi
$unset CDPATH || CDPATH=:
</PRE>
See section <A HREF="autoconf.html#SEC117">Special Shell Variables</A>, for some neutralizing values. Also, see
section <A HREF="autoconf.html#SEC118">Limitations of Shell Builtins</A>, documentation of @command{export}, for
the case of environment variables.
</DL>
<H2><A NAME="SEC119" HREF="autoconf_toc.html#TOC119">Limitations of Usual Tools</A></H2>
<P>
The small set of tools you can expect to find on any machine can still
include some limitations you should be aware of.
<DL COMPACT>
<DT>@command{awk}
<DD>
<A NAME="IDX731"></A>
Don't leave white spaces before the parentheses in user functions calls,
GNU awk will reject it:
<PRE>
$ <KBD>gawk 'function die () { print "Aaaaarg!" }
BEGIN { die () }'</KBD>
gawk: cmd. line:2: BEGIN { die () }
gawk: cmd. line:2: ^ parse error
$ <KBD>gawk 'function die () { print "Aaaaarg!" }
BEGIN { die() }'</KBD>
Aaaaarg!
</PRE>
If you want your program to be deterministic, don't depend on <CODE>for</CODE>
on arrays:
<PRE>
$ <KBD>cat for.awk</KBD>
END {
arr["foo"] = 1
arr["bar"] = 1
for (i in arr)
print i
}
$ <KBD>gawk -f for.awk </dev/null</KBD>
foo
bar
$ <KBD>nawk -f for.awk </dev/null</KBD>
bar
foo
</PRE>
Some AWK, such as HPUX 11.0's native one, have regex engines fragile to
inner anchors:
<PRE>
$ <KBD>echo xfoo | $AWK '/foo|^bar/ { print }'</KBD>
$ <KBD>echo bar | $AWK '/foo|^bar/ { print }'</KBD>
bar
$ <KBD>echo xfoo | $AWK '/^bar|foo/ { print }'</KBD>
xfoo
$ <KBD>echo bar | $AWK '/^bar|foo/ { print }'</KBD>
bar
</PRE>
Either do not depend on such patterns (i.e., use <SAMP>`/^(.*foo|bar)/'</SAMP>,
or use a simple test to reject such AWK.
<DT>@command{cat}
<DD>
<A NAME="IDX732"></A>
Don't rely on any option. The option @option{-v}, which displays
non-printing characters, <EM>seems</EM> portable, though.
<DT>@command{cc}
<DD>
When a compilation such as <SAMP>`cc foo.c -o foo'</SAMP> fails, some compilers
(such as CDS on Reliant UNIX) leave a <TT>`foo.o'</TT>.
HP-UX @command{cc} doesn't accept <TT>`.S'</TT> files to preprocess and
assemble. <SAMP>`cc -c foo.S'</SAMP> will appear to succeed, but in fact does
nothing.
<DT>@command{cmp}
<DD>
<A NAME="IDX733"></A>
@command{cmp} performs a raw data comparison of two files, while
@command{diff} compares two text files. Therefore, if you might compare
DOS files, even if only checking whether two files are different, use
@command{diff} to avoid spurious differences due to differences of
newline encoding.
<DT>@command{cp}
<DD>
<A NAME="IDX734"></A>
SunOS @command{cp} does not support @option{-f}, although its
@command{mv} does. It's possible to deduce why @command{mv} and
@command{cp} are different with respect to @option{-f}. @command{mv}
prompts by default before overwriting a read-only file. @command{cp}
does not. Therefore, @command{mv} requires a @option{-f} option, but
@command{cp} does not. @command{mv} and @command{cp} behave differently
with respect to read-only files because the simplest form of
@command{cp} cannot overwrite a read-only file, but the simplest form of
@command{mv} can. This is because @command{cp} opens the target for
write access, whereas @command{mv} simply calls <CODE>link</CODE> (or, in
newer systems, <CODE>rename</CODE>).
<DT>@command{date}
<DD>
<A NAME="IDX735"></A>
Some versions of @command{date} do not recognize special % directives,
and unfortunately, instead of complaining, they just pass them through,
and exit with success:
<PRE>
$ <KBD>uname -a</KBD>
OSF1 medusa.sis.pasteur.fr V5.1 732 alpha
$ <KBD>date "+%s"</KBD>
%s
</PRE>
<DT>@command{diff}
<DD>
<A NAME="IDX736"></A>
Option @option{-u} is nonportable.
Some implementations, such as Tru64's, fail when comparing to
<TT>`/dev/null'</TT>. Use an empty file instead.
<DT>@command{dirname}
<DD>
<A NAME="IDX737"></A>
Not all hosts have a working @command{dirname}, and you should instead
use <CODE>AS_DIRNAME</CODE> (see section <A HREF="autoconf.html#SEC100">Programming in M4sh</A>). For example:
<PRE>
dir=`dirname "$file"` # This is not portable.
dir=`AS_DIRNAME(["$file"])` # This is more portable.
</PRE>
This handles a few subtleties in the standard way required by
POSIX. For example, under UN*X, should <SAMP>`dirname //1'</SAMP> give
<SAMP>`/'</SAMP>? Paul Eggert answers:
<BLOCKQUOTE>
<P>
No, under some older flavors of Unix, leading <SAMP>`//'</SAMP> is a special
path name: it refers to a "super-root" and is used to access other
machines' files. Leading <SAMP>`///'</SAMP>, <SAMP>`////'</SAMP>, etc. are equivalent
to <SAMP>`/'</SAMP>; but leading <SAMP>`//'</SAMP> is special. I think this tradition
started with Apollo Domain/OS, an OS that is still in use on some older
hosts.
<P>
POSIX allows but does not require the special treatment for <SAMP>`//'</SAMP>.
It says that the behavior of dirname on path names of the form
<SAMP>`//([^/]+/*)?'</SAMP> is implementation defined. In these cases, GNU
@command{dirname} returns <SAMP>`/'</SAMP>, but it's more portable to return
<SAMP>`//'</SAMP> as this works even on those older flavors of Unix.
</BLOCKQUOTE>
<DT>@command{egrep}
<DD>
<A NAME="IDX738"></A>
The empty alternative is not portable, use <SAMP>`?'</SAMP> instead. For
instance with Digital Unix v5.0:
<PRE>
> printf "foo\n|foo\n" | egrep '^(|foo|bar)$'
|foo
> printf "bar\nbar|\n" | egrep '^(foo|bar|)$'
bar|
> printf "foo\nfoo|\n|bar\nbar\n" | egrep '^(foo||bar)$'
foo
|bar
</PRE>
@command{egrep} also suffers the limitations of @command{grep}.
<DT>@command{expr}
<DD>
<A NAME="IDX739"></A>
No @command{expr} keyword starts with <SAMP>`x'</SAMP>, so use @samp{expr
x"<VAR>word</VAR>" : 'x<VAR>regex</VAR>'} to keep @command{expr} from
misinterpreting <VAR>word</VAR>.
Don't use <CODE>length</CODE>, <CODE>substr</CODE>, <CODE>match</CODE> and <CODE>index</CODE>.
<DT>@command{expr (<SAMP>`|'</SAMP>)}
<DD>
<A NAME="IDX740"></A>
You can use <SAMP>`|'</SAMP>. Although POSIX does require that <SAMP>`expr
"'</SAMP> return the empty string, it does not specify the result when you
<SAMP>`|'</SAMP> together the empty string (or zero) with the empty string. For
example:
<PRE>
expr '' \| ''
</PRE>
GNU/Linux and POSIX.2-1992 return the empty string for this
case, but traditional Unix returns <SAMP>`0'</SAMP> (Solaris is one such
example). In the latest POSIX draft, the specification has been
changed to match traditional Unix's behavior (which is bizarre, but it's
too late to fix this). Please note that the same problem does arise
when the empty string results from a computation, as in:
<PRE>
expr bar : foo \| foo : bar
</PRE>
Avoid this portability problem by avoiding the empty string.
<DT>@command{expr (<SAMP>`:'</SAMP>)}
<DD>
<A NAME="IDX741"></A>
Don't use <SAMP>`\?'</SAMP>, <SAMP>`\+'</SAMP> and <SAMP>`\|'</SAMP> in patterns, they are
not supported on Solaris.
The POSIX.2-1992 standard is ambiguous as to whether <SAMP>`expr a :
b'</SAMP> (and <SAMP>`expr 'a' : '\(b\)''</SAMP>) output <SAMP>`0'</SAMP> or the empty string.
In practice, it outputs the empty string on most platforms, but portable
scripts should not assume this. For instance, the QNX 4.25 native
@command{expr} returns <SAMP>`0'</SAMP>.
You may believe that one means to get a uniform behavior would be to use
the empty string as a default value:
<PRE>
expr a : b \| ''
</PRE>
unfortunately this behaves exactly as the original expression, see the
<SAMP>`@command{expr'</SAMP> (<SAMP>`:'</SAMP>)} entry for more information.
Older @command{expr} implementations (e.g. SunOS 4 @command{expr} and
Solaris 8 @command{/usr/ucb/expr}) have a silly length limit that causes
@command{expr} to fail if the matched substring is longer than 120
bytes. In this case, you might want to fall back on <SAMP>`echo|sed'</SAMP> if
@command{expr} fails.
Don't leave, there is some more!
The QNX 4.25 @command{expr}, in addition of preferring <SAMP>`0'</SAMP> to
the empty string, has a funny behavior in its exit status: it's always 1
when parentheses are used!
<PRE>
$ <KBD>val=`expr 'a' : 'a'`; echo "$?: $val"</KBD>
0: 1
$ <KBD>val=`expr 'a' : 'b'`; echo "$?: $val"</KBD>
1: 0
$ <KBD>val=`expr 'a' : '\(a\)'`; echo "?: $val"</KBD>
1: a
$ <KBD>val=`expr 'a' : '\(b\)'`; echo "?: $val"</KBD>
1: 0
</PRE>
In practice this can be a big problem if you are ready to catch failures
of @command{expr} programs with some other method (such as using
@command{sed}), since you may get twice the result. For instance
<PRE>
$ <KBD>expr 'a' : '\(a\)' || echo 'a' | sed 's/^\(a\)$/\1/'</KBD>
</PRE>
will output <SAMP>`a'</SAMP> on most hosts, but <SAMP>`aa'</SAMP> on QNX 4.25. A
simple work around consists in testing @command{expr} and use a variable
set to @command{expr} or to @command{false} according to the result.
<DT>@command{find}
<DD>
The option @option{-maxdepth} seems to be GNU specific. Tru64 v5.1,
NetBSD 1.5 and Solaris 2.5 @command{find} commands do not understand it.
The replacement of <SAMP>`{}'</SAMP> is guaranteed only if the argument is
exactly <EM>{}</EM>, not if it's only a part of an argument. For
instance on DU, and HP-UX 10.20 and HP-UX 11:
<PRE>
$ <KBD>touch foo</KBD>
$ <KBD>find . -name foo -exec echo "{}-{}" \;</KBD>
{}-{}
</PRE>
while GNU @command{find} reports <SAMP>`./foo-./foo'</SAMP>.
<DT>@command{grep}
<DD>
<A NAME="IDX742"></A>
Don't use <SAMP>`grep -s'</SAMP> to suppress output, because <SAMP>`grep -s'</SAMP> on
System V does not suppress output, only error messages. Instead,
redirect the standard output and standard error (in case the file
doesn't exist) of <CODE>grep</CODE> to <TT>`/dev/null'</TT>. Check the exit
status of <CODE>grep</CODE> to determine whether it found a match.
Don't use multiple regexps with @option{-e}, as some <CODE>grep</CODE> will only
honor the last pattern (eg., IRIX 6.5 and Solaris 2.5.1). Anyway,
Stardent Vistra SVR4 <CODE>grep</CODE> lacks @option{-e}... Instead, use
alternation and <CODE>egrep</CODE>.
<DT>@command{ln}
<DD>
<A NAME="IDX743"></A>
<A NAME="IDX744"></A>
Don't rely on @command{ln} having a @option{-f} option. Symbolic links
are not available on old systems, use <SAMP>`ln'</SAMP> as a fall back.
For versions of the DJGPP before 2.04, @command{ln} emulates soft links
for executables by generating a stub that in turn calls the real
program. This feature also works with nonexistent files like in the
Unix spec. So <SAMP>`ln -s file link'</SAMP> will generate <TT>`link.exe'</TT>,
which will attempt to call <TT>`file.exe'</TT> if run. But this feature only
works for executables, so <SAMP>`cp -p'</SAMP> is used instead for these
systems. DJGPP versions 2.04 and later have full symlink support.
<DT>@command{mv}
<DD>
<A NAME="IDX745"></A>
<A NAME="IDX746"></A>
The only portable options are @option{-f} and @option{-i}.
Moving individual files between file systems is portable (it was in V6),
but it is not always atomic: when doing <SAMP>`mv new existing'</SAMP>, there's
a critical section where neither the old nor the new version of
<TT>`existing'</TT> actually exists.
Moving directories across mount points is not portable, use @command{cp}
and @command{rm}.
Moving/Deleting open files isn't portable. The following can't be done
on DOS/WIN32:
<PRE>
exec > foo
mv foo bar
</PRE>
nor can
<PRE>
exec > foo
rm -f foo
</PRE>
<DT>@command{sed}
<DD>
<A NAME="IDX747"></A>
Patterns should not include the separator (unless escaped), even as part
of a character class. In conformance with POSIX, the Cray
@command{sed} will reject <SAMP>`s/[^/]*$//'</SAMP>: use <SAMP>`s,[^/]*$,,'</SAMP>.
Sed scripts should not use branch labels longer than 8 characters and
should not contain comments.
Don't include extra <SAMP>`;'</SAMP>, as some @command{sed}, such as NetBSD
1.4.2's, try to interpret the second as a command:
<PRE>
$ <KBD>echo a | sed 's/x/x/;;s/x/x/'</KBD>
sed: 1: "s/x/x/;;s/x/x/": invalid command code ;
</PRE>
Input should have reasonably long lines, since some @command{sed} have
an input buffer limited to 4000 bytes.
Alternation, <SAMP>`\|'</SAMP>, is common but POSIX.2 does not require its
support, so it should be avoided in portable scripts. Solaris 8
@command{sed} does not support alternation; e.g. <SAMP>`sed '/a\|b/d''</SAMP>
deletes only lines that contain the literal string <SAMP>`a|b'</SAMP>.
Anchors (<SAMP>`^'</SAMP> and <SAMP>`$'</SAMP>) inside groups are not portable.
Nested parenthesization in patterns (e.g., <SAMP>`\(\(a*\)b*)\)'</SAMP>) is
quite portable to modern hosts, but is not supported by some older
@command{sed} implementations like SVR3.
Of course the option @option{-e} is portable, but it is not needed. No
valid Sed program can start with a dash, so it does not help
disambiguating. Its sole usefulness is helping enforcing indenting as
in:
<PRE>
sed -e <VAR>instruction-1</VAR> \
-e <VAR>instruction-2</VAR>
</PRE>
as opposed to
<PRE>
sed <VAR>instruction-1</VAR>;<VAR>instruction-2</VAR>
</PRE>
Contrary to yet another urban legend, you may portably use <SAMP>`&'</SAMP> in
the replacement part of the <CODE>s</CODE> command to mean "what was
matched". All descendents of Bell Lab's V7 @command{sed} (at least; we
don't have first hand experience with older @command{sed}s) have
supported it.
<DT>@command{sed (<SAMP>`t'</SAMP>)}
<DD>
<A NAME="IDX748"></A>
Some old systems have @command{sed} that "forget" to reset their
<SAMP>`t'</SAMP> flag when starting a new cycle. For instance on MIPS
RISC/OS, and on IRIX 5.3, if you run the following @command{sed}
script (the line numbers are not actual part of the texts):
<PRE>
s/keep me/kept/g # a
t end # b
s/.*/deleted/g # c
: end # d
</PRE>
on
<PRE>
delete me # 1
delete me # 2
keep me # 3
delete me # 4
</PRE>
you get
<PRE>
deleted
delete me
kept
deleted
</PRE>
instead of
<PRE>
deleted
deleted
kept
deleted
</PRE>
Why? When processing 1, a matches, therefore sets the t flag, b jumps to
d, and the output is produced. When processing line 2, the t flag is
still set (this is the bug). Line a fails to match, but @command{sed}
is not supposed to clear the t flag when a substitution fails. Line b
sees that the flag is set, therefore it clears it, and jumps to d, hence
you get <SAMP>`delete me'</SAMP> instead of <SAMP>`deleted'</SAMP>. When processing 3 t
is clear, a matches, so the flag is set, hence b clears the flags and
jumps. Finally, since the flag is clear, 4 is processed properly.
There are two things one should remind about <SAMP>`t'</SAMP> in @command{sed}.
Firstly, always remember that <SAMP>`t'</SAMP> jumps if <EM>some</EM> substitution
succeeded, not only the immediately preceding substitution, therefore,
always use a fake <SAMP>`t clear; : clear'</SAMP> to reset the t flag where
indeed.
Secondly, you cannot rely on @command{sed} to clear the flag at each new
cycle.
One portable implementation of the script above is:
<PRE>
t clear
: clear
s/keep me/kept/g
t end
s/.*/deleted/g
: end
</PRE>
<DT>@command{touch}
<DD>
<A NAME="IDX749"></A>
On some old BSD systems, @command{touch} or any command that
results in an empty file does not update the timestamps, so use a
command like <CODE>echo</CODE> as a workaround.
GNU @command{touch} 3.16r (and presumably all before that) fails to work
on SunOS 4.1.3 when the empty file is on an NFS-mounted 4.2 volume.
</DL>
<H2><A NAME="SEC120" HREF="autoconf_toc.html#TOC120">Limitations of Make</A></H2>
<P>
Make itself suffers a great number of limitations, only a few of which
being listed here. First of all, remember that since commands are
executed by the shell, all its weaknesses are inherited...
<DL COMPACT>
<DT><CODE>$<</CODE>
<DD>
POSIX says that the <SAMP>`$<'</SAMP> construct in makefiles can be used
only in inference rules and in the <SAMP>`.DEFAULT'</SAMP> rule; its meaning in
ordinary rules is unspecified. Solaris 8's @command{make} for instance
will replace it with the argument.
<DT>Leading underscore in macro names
<DD>
Some Make don't support leading underscores in macro names, such as on
NEWS-OS 4.2R.
<PRE>
$ <KBD>cat Makefile</KBD>
_am_include = #
_am_quote =
all:; @echo this is test
$ <KBD>make</KBD>
Make: Must be a separator on rules line 2. Stop.
$ <KBD>cat Makefile2</KBD>
am_include = #
am_quote =
all:; @echo this is test
$ <KBD>make -f Makefile2</KBD>
this is test
</PRE>
<DT><CODE>VPATH</CODE>
<DD>
<A NAME="IDX750"></A>
Don't use it! For instance any assignment to <CODE>VPATH</CODE> causes Sun
@command{make} to only execute the first set of double-colon rules.
</DL>
<H1><A NAME="SEC121" HREF="autoconf_toc.html#TOC121">Manual Configuration</A></H1>
<P>
A few kinds of features can't be guessed automatically by running test
programs. For example, the details of the object-file format, or
special options that need to be passed to the compiler or linker. You
can check for such features using ad-hoc means, such as having
@command{configure} check the output of the <CODE>uname</CODE> program, or
looking for libraries that are unique to particular systems. However,
Autoconf provides a uniform method for handling unguessable features.
<H2><A NAME="SEC122" HREF="autoconf_toc.html#TOC122">Specifying the System Type</A></H2>
<P>
Like other GNU @command{configure} scripts, Autoconf-generated
@command{configure} scripts can make decisions based on a canonical name
for the system type, which has the form:
<SAMP>`<VAR>cpu</VAR>-<VAR>vendor</VAR>-<VAR>os</VAR>'</SAMP>, where <VAR>os</VAR> can be
<SAMP>`<VAR>system</VAR>'</SAMP> or <SAMP>`<VAR>kernel</VAR>-<VAR>system</VAR>'</SAMP>
<P>
@command{configure} can usually guess the canonical name for the type of
system it's running on. To do so it runs a script called
@command{config.guess}, which infers the name using the <CODE>uname</CODE>
command or symbols predefined by the C preprocessor.
<P>
Alternately, the user can specify the system type with command line
arguments to @command{configure}. Doing so is necessary when
cross-compiling. In the most complex case of cross-compiling, three
system types are involved. The options to specify them are:
<DL COMPACT>
<DT>@option{--build=<VAR>build-type</VAR>}
<DD>
the type of system on which the package is being configured and
compiled. It defaults to the result of running @command{config.guess}.
<DT>@option{--host=<VAR>host-type</VAR>}
<DD>
<A NAME="IDX751"></A>
the type of system on which the package will run. By default it is the
same as the build machine. Specifying it enables the cross-compilation
mode.
<DT>@option{--target=<VAR>target-type</VAR>}
<DD>
the type of system for which any compiler tools in the package will
produce code (rarely needed). By default, it is the same as host.
</DL>
<P>
If you mean to override the result of @command{config.guess}, use
@option{--build}, not @option{--host}, since the latter enables
cross-compilation. For historical reasons, passing @option{--host} also
changes the build type. Therefore, whenever you specify <CODE>--host</CODE>,
be sure to specify <CODE>--build</CODE> too. This will be fixed in the
future.
<PRE>
./configure --build=i686-pc-linux-gnu --host=m68k-coff
</PRE>
<P>
will enter cross-compilation mode, but @command{configure} will fail if it
can't run the code generated by the specified compiler if you configure
as follows:
<PRE>
./configure CC=m68k-coff-gcc
</PRE>
<P>
<A NAME="IDX752"></A>
@command{configure} recognizes short aliases for many system types; for
example, <SAMP>`decstation'</SAMP> can be used instead of
<SAMP>`mips-dec-ultrix4.2'</SAMP>. @command{configure} runs a script called
@command{config.sub} to canonicalize system type aliases.
<P>
This section deliberately omits the description of the obsolete
interface, see section <A HREF="autoconf.html#SEC160">Hosts and Cross-Compilation</A>.
<H2><A NAME="SEC123" HREF="autoconf_toc.html#TOC123">Getting the Canonical System Type</A></H2>
<P>
The following macros make the system type available to @command{configure}
scripts.
<P>
<A NAME="IDX753"></A>
<A NAME="IDX754"></A>
<A NAME="IDX755"></A>
<P>
The variables <SAMP>`build_alias'</SAMP>, <SAMP>`host_alias'</SAMP>, and
<SAMP>`target_alias'</SAMP> are always exactly the arguments of @option{--build},
@option{--host}, and @option{--target}; in particular, they are left empty
if the user did not use them, even if the corresponding
<CODE>AC_CANONICAL</CODE> macro was run. Any configure script may use these
variables anywhere. These are the variables that should be used when in
interaction with the user.
<P>
If you need to recognize some special environments based on their system
type, run the following macros to get canonical system names. These
variables are not set before the macro call.
<P>
If you use these macros, you must distribute @command{config.guess} and
@command{config.sub} along with your source code. See section <A HREF="autoconf.html#SEC19">Outputting Files</A>, for
information about the <CODE>AC_CONFIG_AUX_DIR</CODE> macro which you can use
to control in which directory @command{configure} looks for those scripts.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CANONICAL_BUILD</B>
<DD><A NAME="IDX756"></A>
<A NAME="IDX757"></A>
<A NAME="IDX758"></A>
<A NAME="IDX759"></A>
<A NAME="IDX760"></A>
<A NAME="IDX761"></A>
Compute the canonical build-system type variable, <CODE>build</CODE>, and its
three individual parts <CODE>build_cpu</CODE>, <CODE>build_vendor</CODE>, and
<CODE>build_os</CODE>.
<P>
If @option{--build} was specified, then <CODE>build</CODE> is the
canonicalization of <CODE>build_alias</CODE> by @command{config.sub},
otherwise it is determined by the shell script @command{config.guess}.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CANONICAL_HOST</B>
<DD><A NAME="IDX762"></A>
<A NAME="IDX763"></A>
<A NAME="IDX764"></A>
<A NAME="IDX765"></A>
<A NAME="IDX766"></A>
<A NAME="IDX767"></A>
Compute the canonical host-system type variable, <CODE>host</CODE>, and its
three individual parts <CODE>host_cpu</CODE>, <CODE>host_vendor</CODE>, and
<CODE>host_os</CODE>.
<P>
If @option{--host} was specified, then <CODE>host</CODE> is the
canonicalization of <CODE>host_alias</CODE> by @command{config.sub},
otherwise it defaults to <CODE>build</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CANONICAL_TARGET</B>
<DD><A NAME="IDX768"></A>
<A NAME="IDX769"></A>
<A NAME="IDX770"></A>
<A NAME="IDX771"></A>
<A NAME="IDX772"></A>
<A NAME="IDX773"></A>
Compute the canonical target-system type variable, <CODE>target</CODE>, and its
three individual parts <CODE>target_cpu</CODE>, <CODE>target_vendor</CODE>, and
<CODE>target_os</CODE>.
<P>
If @option{--target} was specified, then <CODE>target</CODE> is the
canonicalization of <CODE>target_alias</CODE> by @command{config.sub},
otherwise it defaults to <CODE>host</CODE>.
</DL>
<P>
Note that there can be artifacts due to the backward compatibility
code. See section <A HREF="autoconf.html#SEC160">Hosts and Cross-Compilation</A>, for more.
<H2><A NAME="SEC124" HREF="autoconf_toc.html#TOC124">Using the System Type</A></H2>
<P>
How do you use a canonical system type? Usually, you use it in one or
more <CODE>case</CODE> statements in <TT>`configure.ac'</TT> to select
system-specific C files. Then, using <CODE>AC_CONFIG_LINKS</CODE>, link those
files which have names based on the system name, to generic names, such
as <TT>`host.h'</TT> or <TT>`target.c'</TT> (see section <A HREF="autoconf.html#SEC32">Creating Configuration Links</A>). The
<CODE>case</CODE> statement patterns can use shell wild cards to group several
cases together, like in this fragment:
<PRE>
case $target in
i386-*-mach* | i386-*-gnu*)
obj_format=aout emulation=mach bfd_gas=yes ;;
i960-*-bout) obj_format=bout ;;
esac
</PRE>
<P>
and later in <TT>`configure.ac'</TT>, use:
<PRE>
AC_CONFIG_LINKS(host.h:config/$machine.h
object.h:config/$obj_format.h)
</PRE>
<P>
Note that the above example uses <CODE>$target</CODE> because it's taken from
a tool which can be built on some architecture (<CODE>$build</CODE>), run on
another (<CODE>$host</CODE>), but yet handle data for a third architecture
(<CODE>$target</CODE>). Such tools are usually part of a compiler suite, they
generate code for a specific <CODE>$target</CODE>.
<P>
However <CODE>$target</CODE> should be meaningless for most packages. If you
want to base a decision on the system where your program will be run,
make sure you use the <CODE>$host</CODE> variable, as in the following
excerpt:
<PRE>
case $host in
*-*-msdos* | *-*-go32* | *-*-mingw32* | *-*-cygwin* | *-*-windows*)
MUMBLE_INIT="mumble.ini"
;;
*)
MUMBLE_INIT=".mumbleinit"
;;
esac
AC_SUBST([MUMBLE_INIT])
</PRE>
<P>
You can also use the host system type to find cross-compilation tools.
See section <A HREF="autoconf.html#SEC41">Generic Program and File Checks</A>, for information about the <CODE>AC_CHECK_TOOL</CODE>
macro which does that.
<H1><A NAME="SEC125" HREF="autoconf_toc.html#TOC125">Site Configuration</A></H1>
<P>
@command{configure} scripts support several kinds of local configuration
decisions. There are ways for users to specify where external software
packages are, include or exclude optional features, install programs
under modified names, and set default values for @command{configure}
options.
<H2><A NAME="SEC126" HREF="autoconf_toc.html#TOC126">Working With External Software</A></H2>
<P>
Some packages require, or can optionally use, other software packages
that are already installed. The user can give @command{configure}
command line options to specify which such external software to use.
The options have one of these forms:
<PRE>
--with-<VAR>package</VAR>[=<VAR>arg</VAR>]
--without-<VAR>package</VAR>
</PRE>
<P>
For example, @option{--with-gnu-ld} means work with the GNU linker
instead of some other linker. @option{--with-x} means work with The X
Window System.
<P>
The user can give an argument by following the package name with
<SAMP>`='</SAMP> and the argument. Giving an argument of <SAMP>`no'</SAMP> is for
packages that are used by default; it says to <EM>not</EM> use the
package. An argument that is neither <SAMP>`yes'</SAMP> nor <SAMP>`no'</SAMP> could
include a name or number of a version of the other package, to specify
more precisely which other package this program is supposed to work
with. If no argument is given, it defaults to <SAMP>`yes'</SAMP>.
@option{--without-<VAR>package</VAR>} is equivalent to
@option{--with-<VAR>package</VAR>=no}.
<P>
@command{configure} scripts do not complain about
@option{--with-<VAR>package</VAR>} options that they do not support. This
behavior permits configuring a source tree containing multiple packages
with a top-level @command{configure} script when the packages support
different options, without spurious error messages about options that
some of the packages support. An unfortunate side effect is that option
spelling errors are not diagnosed. No better approach to this problem
has been suggested so far.
<P>
For each external software package that may be used, <TT>`configure.ac'</TT>
should call <CODE>AC_ARG_WITH</CODE> to detect whether the @command{configure}
user asked to use it. Whether each package is used or not by default,
and which arguments are valid, is up to you.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_ARG_WITH</B> <I>(<VAR>package</VAR>, <VAR>help-string</VAR>, @ovar{action-if-given}, @ovar{action-if-not-given})</I>
<DD><A NAME="IDX774"></A>
<A NAME="IDX775"></A>
If the user gave @command{configure} the option @option{--with-<VAR>package</VAR>}
or @option{--without-<VAR>package</VAR>}, run shell commands
<VAR>action-if-given</VAR>. If neither option was given, run shell commands
<VAR>action-if-not-given</VAR>. The name <VAR>package</VAR> indicates another
software package that this program should work with. It should consist
only of alphanumeric characters and dashes.
<P>
The option's argument is available to the shell commands
<VAR>action-if-given</VAR> in the shell variable <CODE>withval</CODE>, which is
actually just the value of the shell variable <CODE>with_<VAR>package</VAR></CODE>,
with any @option{-} characters changed into <SAMP>`_'</SAMP>. You may use that
variable instead, if you wish.
<P>
The argument <VAR>help-string</VAR> is a description of the option that
looks like this:
<PRE>
--with-readline support fancy command line editing
</PRE>
<P>
<VAR>help-string</VAR> may be more than one line long, if more detail is
needed. Just make sure the columns line up in <SAMP>`configure --help'</SAMP>.
Avoid tabs in the help string. You'll need to enclose it in <SAMP>`['</SAMP>
and <SAMP>`]'</SAMP> in order to produce the leading spaces.
<P>
You should format your <VAR>help-string</VAR> with the macro
<CODE>AC_HELP_STRING</CODE> (see section <A HREF="autoconf.html#SEC128">Making Your Help Strings Look Pretty</A>).
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_WITH</B> <I>(<VAR>package</VAR>, <VAR>action-if-given</VAR>, @ovar{action-if-not-given})</I>
<DD><A NAME="IDX776"></A>
<A NAME="IDX777"></A>
This is an obsolete version of <CODE>AC_ARG_WITH</CODE> that does not
support providing a help string.
</DL>
<H2><A NAME="SEC127" HREF="autoconf_toc.html#TOC127">Choosing Package Options</A></H2>
<P>
If a software package has optional compile-time features, the user can
give @command{configure} command line options to specify whether to
compile them. The options have one of these forms:
<PRE>
--enable-<VAR>feature</VAR>[=<VAR>arg</VAR>]
--disable-<VAR>feature</VAR>
</PRE>
<P>
These options allow users to choose which optional features to build and
install. @option{--enable-<VAR>feature</VAR>} options should never make a
feature behave differently or cause one feature to replace another.
They should only cause parts of the program to be built rather than left
out.
<P>
The user can give an argument by following the feature name with
<SAMP>`='</SAMP> and the argument. Giving an argument of <SAMP>`no'</SAMP> requests
that the feature <EM>not</EM> be made available. A feature with an
argument looks like @option{--enable-debug=stabs}. If no argument is
given, it defaults to <SAMP>`yes'</SAMP>. @option{--disable-<VAR>feature</VAR>} is
equivalent to @option{--enable-<VAR>feature</VAR>=no}.
<P>
@command{configure} scripts do not complain about
@option{--enable-<VAR>feature</VAR>} options that they do not support.
This behavior permits configuring a source tree containing multiple
packages with a top-level @command{configure} script when the packages
support different options, without spurious error messages about options
that some of the packages support.
An unfortunate side effect is that option spelling errors are not diagnosed.
No better approach to this problem has been suggested so far.
<P>
For each optional feature, <TT>`configure.ac'</TT> should call
<CODE>AC_ARG_ENABLE</CODE> to detect whether the @command{configure} user asked
to include it. Whether each feature is included or not by default, and
which arguments are valid, is up to you.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_ARG_ENABLE</B> <I>(<VAR>feature</VAR>, <VAR>help-string</VAR>, @ovar{action-if-given}, @ovar{action-if-not-given})</I>
<DD><A NAME="IDX778"></A>
<A NAME="IDX779"></A>
If the user gave @command{configure} the option
@option{--enable-<VAR>feature</VAR>} or @option{--disable-<VAR>feature</VAR>}, run
shell commands <VAR>action-if-given</VAR>. If neither option was given, run
shell commands <VAR>action-if-not-given</VAR>. The name <VAR>feature</VAR>
indicates an optional user-level facility. It should consist only of
alphanumeric characters and dashes.
<P>
The option's argument is available to the shell commands
<VAR>action-if-given</VAR> in the shell variable <CODE>enableval</CODE>, which is
actually just the value of the shell variable
<CODE>enable_<VAR>feature</VAR></CODE>, with any @option{-} characters changed into
<SAMP>`_'</SAMP>. You may use that variable instead, if you wish. The
<VAR>help-string</VAR> argument is like that of <CODE>AC_ARG_WITH</CODE>
(see section <A HREF="autoconf.html#SEC126">Working With External Software</A>).
<P>
You should format your <VAR>help-string</VAR> with the macro
<CODE>AC_HELP_STRING</CODE> (see section <A HREF="autoconf.html#SEC128">Making Your Help Strings Look Pretty</A>).
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_ENABLE</B> <I>(<VAR>feature</VAR>, <VAR>action-if-given</VAR>, @ovar{action-if-not-given})</I>
<DD><A NAME="IDX780"></A>
<A NAME="IDX781"></A>
This is an obsolete version of <CODE>AC_ARG_ENABLE</CODE> that does not
support providing a help string.
</DL>
<H2><A NAME="SEC128" HREF="autoconf_toc.html#TOC128">Making Your Help Strings Look Pretty</A></H2>
<P>
Properly formatting the <SAMP>`help strings'</SAMP> which are used in
<CODE>AC_ARG_WITH</CODE> (see section <A HREF="autoconf.html#SEC126">Working With External Software</A>) and <CODE>AC_ARG_ENABLE</CODE>
(see section <A HREF="autoconf.html#SEC127">Choosing Package Options</A>) can be challenging. Specifically, you want
your own <SAMP>`help strings'</SAMP> to line up in the appropriate columns of
<SAMP>`configure --help'</SAMP> just like the standard Autoconf <SAMP>`help
strings'</SAMP> do. This is the purpose of the <CODE>AC_HELP_STRING</CODE> macro.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_HELP_STRING</B> <I>(<VAR>left-hand-side</VAR>, <VAR>right-hand-side</VAR>)</I>
<DD><A NAME="IDX782"></A>
<A NAME="IDX783"></A>
<P>
Expands into an help string that looks pretty when the user executes
<SAMP>`configure --help'</SAMP>. It is typically used in <CODE>AC_ARG_WITH</CODE>
(see section <A HREF="autoconf.html#SEC126">Working With External Software</A>) or <CODE>AC_ARG_ENABLE</CODE> (see section <A HREF="autoconf.html#SEC127">Choosing Package Options</A>). The following example will make this clearer.
<PRE>
AC_DEFUN(TEST_MACRO,
[AC_ARG_WITH(foo,
AC_HELP_STRING([--with-foo],
[use foo (default is NO)]),
ac_cv_use_foo=$withval, ac_cv_use_foo=no),
AC_CACHE_CHECK(whether to use foo,
ac_cv_use_foo, ac_cv_use_foo=no)])
</PRE>
<P>
Please note that the call to <CODE>AC_HELP_STRING</CODE> is <STRONG>unquoted</STRONG>.
Then the last few lines of <SAMP>`configure --help'</SAMP> will appear like
this:
<PRE>
--enable and --with options recognized:
--with-foo use foo (default is NO)
</PRE>
<P>
The <CODE>AC_HELP_STRING</CODE> macro is particularly helpful when the
<VAR>left-hand-side</VAR> and/or <VAR>right-hand-side</VAR> are composed of macro
arguments, as shown in the following example.
<PRE>
AC_DEFUN(MY_ARG_WITH,
[AC_ARG_WITH([$1],
AC_HELP_STRING([--with-$1], [use $1 (default is $2)]),
ac_cv_use_$1=$withval, ac_cv_use_$1=no),
AC_CACHE_CHECK(whether to use $1, ac_cv_use_$1, ac_cv_use_$1=$2)])
</PRE>
</DL>
<H2><A NAME="SEC129" HREF="autoconf_toc.html#TOC129">Configuring Site Details</A></H2>
<P>
Some software packages require complex site-specific information. Some
examples are host names to use for certain services, company names, and
email addresses to contact. Since some configuration scripts generated
by Metaconfig ask for such information interactively, people sometimes
wonder how to get that information in Autoconf-generated configuration
scripts, which aren't interactive.
<P>
Such site configuration information should be put in a file that is
edited <EM>only by users</EM>, not by programs. The location of the file
can either be based on the <CODE>prefix</CODE> variable, or be a standard
location such as the user's home directory. It could even be specified
by an environment variable. The programs should examine that file at
run time, rather than at compile time. Run time configuration is more
convenient for users and makes the configuration process simpler than
getting the information while configuring. See section `Variables for Installation Directories' in <CITE>GNU Coding Standards</CITE>, for more information on where to put data files.
<H2><A NAME="SEC130" HREF="autoconf_toc.html#TOC130">Transforming Program Names When Installing</A></H2>
<P>
Autoconf supports changing the names of programs when installing them.
In order to use these transformations, <TT>`configure.ac'</TT> must call the
macro <CODE>AC_ARG_PROGRAM</CODE>.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_ARG_PROGRAM</B>
<DD><A NAME="IDX784"></A>
<A NAME="IDX785"></A>
<A NAME="IDX786"></A>
Place in output variable <CODE>program_transform_name</CODE> a sequence of
<CODE>sed</CODE> commands for changing the names of installed programs.
<P>
If any of the options described below are given to @command{configure},
program names are transformed accordingly. Otherwise, if
<CODE>AC_CANONICAL_TARGET</CODE> has been called and a @option{--target} value
is given, the target type followed by a dash is used as a prefix.
Otherwise, no program name transformation is done.
</DL>
<H3><A NAME="SEC131" HREF="autoconf_toc.html#TOC131">Transformation Options</A></H3>
<P>
You can specify name transformations by giving @command{configure} these
command line options:
<DL COMPACT>
<DT>@option{--program-prefix=<VAR>prefix</VAR>}
<DD>
prepend <VAR>prefix</VAR> to the names;
<DT>@option{--program-suffix=<VAR>suffix</VAR>}
<DD>
append <VAR>suffix</VAR> to the names;
<DT>@option{--program-transform-name=<VAR>expression</VAR>}
<DD>
perform <CODE>sed</CODE> substitution <VAR>expression</VAR> on the names.
</DL>
<H3><A NAME="SEC132" HREF="autoconf_toc.html#TOC132">Transformation Examples</A></H3>
<P>
These transformations are useful with programs that can be part of a
cross-compilation development environment. For example, a
cross-assembler running on a Sun 4 configured with
@option{--target=i960-vxworks} is normally installed as
<TT>`i960-vxworks-as'</TT>, rather than <TT>`as'</TT>, which could be confused
with a native Sun 4 assembler.
<P>
You can force a program name to begin with <TT>`g'</TT>, if you don't want
GNU programs installed on your system to shadow other programs with
the same name. For example, if you configure GNU <CODE>diff</CODE> with
@option{--program-prefix=g}, then when you run <SAMP>`make install'</SAMP> it is
installed as <TT>`/usr/local/bin/gdiff'</TT>.
<P>
As a more sophisticated example, you could use
<PRE>
--program-transform-name='s/^/g/; s/^gg/g/; s/^gless/less/'
</PRE>
<P>
<P>
to prepend <SAMP>`g'</SAMP> to most of the program names in a source tree,
excepting those like <CODE>gdb</CODE> that already have one and those like
<CODE>less</CODE> and <CODE>lesskey</CODE> that aren't GNU programs. (That is
assuming that you have a source tree containing those programs that is
set up to use this feature.)
<P>
One way to install multiple versions of some programs simultaneously is
to append a version number to the name of one or both. For example, if
you want to keep Autoconf version 1 around for awhile, you can configure
Autoconf version 2 using @option{--program-suffix=2} to install the
programs as <TT>`/usr/local/bin/autoconf2'</TT>,
<TT>`/usr/local/bin/autoheader2'</TT>, etc. Nevertheless, pay attention
that only the binaries are renamed, therefore you'd have problems with
the library files which might overlap.
<H3><A NAME="SEC133" HREF="autoconf_toc.html#TOC133">Transformation Rules</A></H3>
<P>
Here is how to use the variable <CODE>program_transform_name</CODE> in a
<TT>`Makefile.in'</TT>:
<PRE>
PROGRAMS = cp ls rm
transform = @program_transform_name@
install:
for p in $(PROGRAMS); do \
$(INSTALL_PROGRAM) $$p $(DESTDIR)$(bindir)/`echo $$p | \
sed '$(transform)'`; \
done
uninstall:
for p in $(PROGRAMS); do \
rm -f $(DESTDIR)$(bindir)/`echo $$p | sed '$(transform)'`; \
done
</PRE>
<P>
It is guaranteed that <CODE>program_transform_name</CODE> is never empty, and
that there are no useless separators. Therefore you may safely embed
<CODE>program_transform_name</CODE> within a sed program using <SAMP>`;'</SAMP>:
<PRE>
transform = @program_transform_name@
transform_exe = s/$(EXEEXT)$$//;$(transform);s/$$/$(EXEEXT)/
</PRE>
<P>
Whether to do the transformations on documentation files (Texinfo or
<CODE>man</CODE>) is a tricky question; there seems to be no perfect answer,
due to the several reasons for name transforming. Documentation is not
usually particular to a specific architecture, and Texinfo files do not
conflict with system documentation. But they might conflict with
earlier versions of the same files, and <CODE>man</CODE> pages sometimes do
conflict with system documentation. As a compromise, it is probably
best to do name transformations on <CODE>man</CODE> pages but not on Texinfo
manuals.
<H2><A NAME="SEC134" HREF="autoconf_toc.html#TOC134">Setting Site Defaults</A></H2>
<P>
Autoconf-generated @command{configure} scripts allow your site to provide
default values for some configuration values. You do this by creating
site- and system-wide initialization files.
<P>
<A NAME="IDX787"></A>
If the environment variable @command{CONFIG_SITE} is set, @command{configure}
uses its value as the name of a shell script to read. Otherwise, it
reads the shell script <TT>`<VAR>prefix</VAR>/share/config.site'</TT> if it exists,
then <TT>`<VAR>prefix</VAR>/etc/config.site'</TT> if it exists. Thus,
settings in machine-specific files override those in machine-independent
ones in case of conflict.
<P>
Site files can be arbitrary shell scripts, but only certain kinds of
code are really appropriate to be in them. Because @command{configure}
reads any cache file after it has read any site files, a site file can
define a default cache file to be shared between all Autoconf-generated
@command{configure} scripts run on that system (see section <A HREF="autoconf.html#SEC84">Cache Files</A>). If
you set a default cache file in a site file, it is a good idea to also
set the output variable <CODE>CC</CODE> in that site file, because the cache
file is only valid for a particular compiler, but many systems have
several available.
<P>
You can examine or override the value set by a command line option to
@command{configure} in a site file; options set shell variables that have
the same names as the options, with any dashes turned into underscores.
The exceptions are that @option{--without-} and @option{--disable-} options
are like giving the corresponding @option{--with-} or @option{--enable-}
option and the value <SAMP>`no'</SAMP>. Thus, @option{--cache-file=localcache}
sets the variable <CODE>cache_file</CODE> to the value <SAMP>`localcache'</SAMP>;
@option{--enable-warnings=no} or @option{--disable-warnings} sets the variable
<CODE>enable_warnings</CODE> to the value <SAMP>`no'</SAMP>; @option{--prefix=/usr} sets the
variable <CODE>prefix</CODE> to the value <SAMP>`/usr'</SAMP>; etc.
<P>
Site files are also good places to set default values for other output
variables, such as <CODE>CFLAGS</CODE>, if you need to give them non-default
values: anything you would normally do, repetitively, on the command
line. If you use non-default values for <VAR>prefix</VAR> or
<VAR>exec_prefix</VAR> (wherever you locate the site file), you can set them
in the site file if you specify it with the @command{CONFIG_SITE}
environment variable.
<P>
You can set some cache values in the site file itself. Doing this is
useful if you are cross-compiling, so it is impossible to check features
that require running a test program. You could "prime the cache" by
setting those values correctly for that system in
<TT>`<VAR>prefix</VAR>/etc/config.site'</TT>. To find out the names of the cache
variables you need to set, look for shell variables with <SAMP>`_cv_'</SAMP> in
their names in the affected @command{configure} scripts, or in the Autoconf
M4 source code for those macros.
<P>
The cache file is careful to not override any variables set in the site
files. Similarly, you should not override command-line options in the
site files. Your code should check that variables such as <CODE>prefix</CODE>
and <CODE>cache_file</CODE> have their default values (as set near the top of
@command{configure}) before changing them.
<P>
Here is a sample file <TT>`/usr/share/local/gnu/share/config.site'</TT>. The
command <SAMP>`configure --prefix=/usr/share/local/gnu'</SAMP> would read this
file (if @command{CONFIG_SITE} is not set to a different file).
<PRE>
# config.site for configure
#
# Change some defaults.
test "$prefix" = NONE && prefix=/usr/share/local/gnu
test "$exec_prefix" = NONE && exec_prefix=/usr/local/gnu
test "$sharedstatedir" = '$prefix/com' && sharedstatedir=/var
test "$localstatedir" = '$prefix/var' && localstatedir=/var
# Give Autoconf 2.x generated configure scripts a shared default
# cache file for feature test results, architecture-specific.
if test "$cache_file" = /dev/null; then
cache_file="$prefix/var/config.cache"
# A cache file is only valid for one C compiler.
CC=gcc
fi
</PRE>
<H1><A NAME="SEC135" HREF="autoconf_toc.html#TOC135">Running @command{configure} Scripts</A></H1>
<P>
<A NAME="IDX788"></A>
<P>
Below are instructions on how to configure a package that uses a
@command{configure} script, suitable for inclusion as an <TT>`INSTALL'</TT>
file in the package. A plain-text version of <TT>`INSTALL'</TT> which you
may use comes with Autoconf.
<H2><A NAME="SEC136" HREF="autoconf_toc.html#TOC136">Basic Installation</A></H2>
<P>
These are generic installation instructions.
<P>
The @command{configure} shell script attempts to guess correct values
for various system-dependent variables used during compilation. It uses
those values to create a <TT>`Makefile'</TT> in each directory of the
package. It may also create one or more <TT>`.h'</TT> files containing
system-dependent definitions. Finally, it creates a shell script
<TT>`config.status'</TT> that you can run in the future to recreate the
current configuration, and a file <TT>`config.log'</TT> containing compiler
output (useful mainly for debugging @command{configure}).
<P>
It can also use an optional file (typically called <TT>`config.cache'</TT>
and enabled with @option{--cache-file=config.cache} or simply
@option{-C}) that saves the results of its tests to speed up
reconfiguring. (Caching is disabled by default to prevent problems with
accidental use of stale cache files.)
<P>
If you need to do unusual things to compile the package, please try to
figure out how @command{configure} could check whether to do them, and
mail diffs or instructions to the address given in the <TT>`README'</TT> so
they can be considered for the next release. If you are using the
cache, and at some point <TT>`config.cache'</TT> contains results you don't
want to keep, you may remove or edit it.
<P>
The file <TT>`configure.ac'</TT> (or <TT>`configure.in'</TT>) is used to create
<TT>`configure'</TT> by a program called <CODE>autoconf</CODE>. You only need
<TT>`configure.ac'</TT> if you want to change it or regenerate
<TT>`configure'</TT> using a newer version of <CODE>autoconf</CODE>.
<P>
The simplest way to compile this package is:
<OL>
<LI>
<CODE>cd</CODE> to the directory containing the package's source code and type
<SAMP>`./configure'</SAMP> to configure the package for your system. If you're
using <CODE>csh</CODE> on an old version of System V, you might need to type
<SAMP>`sh ./configure'</SAMP> instead to prevent <CODE>csh</CODE> from trying to
execute @command{configure} itself.
Running @command{configure} takes awhile. While running, it prints some
messages telling which features it is checking for.
<LI>
Type <SAMP>`make'</SAMP> to compile the package.
<LI>
Optionally, type <SAMP>`make check'</SAMP> to run any self-tests that come with
the package.
<LI>
Type <SAMP>`make install'</SAMP> to install the programs and any data files and
documentation.
<LI>
You can remove the program binaries and object files from the source
code directory by typing <SAMP>`make clean'</SAMP>. To also remove the files
that @command{configure} created (so you can compile the package for a
different kind of computer), type <SAMP>`make distclean'</SAMP>. There is also
a <SAMP>`make maintainer-clean'</SAMP> target, but that is intended mainly for
the package's developers. If you use it, you may have to get all sorts
of other programs in order to regenerate files that came with the
distribution.
</OL>
<H2><A NAME="SEC137" HREF="autoconf_toc.html#TOC137">Compilers and Options</A></H2>
<P>
Some systems require unusual options for compilation or linking that the
@command{configure} script does not know about. Run @samp{./configure
--help} for details on some of the pertinent environment variables.
<P>
You can give @command{configure} initial values for variables by setting
them in the environment. You can do that on the command line like this:
<PRE>
./configure CC=c89 CFLAGS=-O2 LIBS=-lposix
</PRE>
<P>
See section <A HREF="autoconf.html#SEC143">Defining Variables</A>, for more details.
<H2><A NAME="SEC138" HREF="autoconf_toc.html#TOC138">Compiling For Multiple Architectures</A></H2>
<P>
You can compile the package for more than one kind of computer at the
same time, by placing the object files for each architecture in their
own directory. To do this, you must use a version of @command{make}
that supports the <CODE>VPATH</CODE> variable, such as GNU @command{make}.
@command{cd} to the directory where you want the object files and
executables to go and run the @command{configure} script.
@command{configure} automatically checks for the source code in the
directory that @command{configure} is in and in <TT>`..'</TT>.
<P>
If you have to use a @command{make} that does not support the
<CODE>VPATH</CODE> variable, you have to compile the package for one
architecture at a time in the source code directory. After you have
installed the package for one architecture, use <SAMP>`make distclean'</SAMP>
before reconfiguring for another architecture.
<H2><A NAME="SEC139" HREF="autoconf_toc.html#TOC139">Installation Names</A></H2>
<P>
By default, <SAMP>`make install'</SAMP> will install the package's files in
<TT>`/usr/local/bin'</TT>, <TT>`/usr/local/man'</TT>, etc. You can specify an
installation prefix other than <TT>`/usr/local'</TT> by giving
@command{configure} the option @option{--prefix=<VAR>path</VAR>}.
<P>
You can specify separate installation prefixes for architecture-specific
files and architecture-independent files. If you give
@command{configure} the option @option{--exec-prefix=<VAR>path</VAR>}, the
package will use <VAR>path</VAR> as the prefix for installing programs and
libraries. Documentation and other data files will still use the
regular prefix.
<P>
In addition, if you use an unusual directory layout you can give options
like @option{--bindir=<VAR>path</VAR>} to specify different values for
particular kinds of files. Run <SAMP>`configure --help'</SAMP> for a list of
the directories you can set and what kinds of files go in them.
<P>
If the package supports it, you can cause programs to be installed with
an extra prefix or suffix on their names by giving @command{configure}
the option @option{--program-prefix=<VAR>PREFIX</VAR>} or
@option{--program-suffix=<VAR>SUFFIX</VAR>}.
<H2><A NAME="SEC140" HREF="autoconf_toc.html#TOC140">Optional Features</A></H2>
<P>
Some packages pay attention to @option{--enable-<VAR>feature</VAR>} options
to @command{configure}, where <VAR>feature</VAR> indicates an optional part
of the package. They may also pay attention to
@option{--with-<VAR>package</VAR>} options, where <VAR>package</VAR> is something
like <SAMP>`gnu-as'</SAMP> or <SAMP>`x'</SAMP> (for the X Window System). The
<TT>`README'</TT> should mention any @option{--enable-} and @option{--with-}
options that the package recognizes.
<P>
For packages that use the X Window System, @command{configure} can
usually find the X include and library files automatically, but if it
doesn't, you can use the @command{configure} options
@option{--x-includes=<VAR>dir</VAR>} and @option{--x-libraries=<VAR>dir</VAR>} to
specify their locations.
<H2><A NAME="SEC141" HREF="autoconf_toc.html#TOC141">Specifying the System Type</A></H2>
<P>
There may be some features @command{configure} cannot figure out
automatically, but needs to determine by the type of machine the package
will run on. Usually, assuming the package is built to be run on the
<EM>same</EM> architectures, @command{configure} can figure that out, but
if it prints a message saying it cannot guess the machine type, give it
the @option{--build=<VAR>type</VAR>} option. <VAR>type</VAR> can either be a
short name for the system type, such as <SAMP>`sun4'</SAMP>, or a canonical name
which has the form:
<PRE>
<VAR>cpu</VAR>-<VAR>company</VAR>-<VAR>system</VAR>
</PRE>
<P>
where <VAR>system</VAR> can have one of these forms:
<PRE>
<VAR>os</VAR> <VAR>kernel</VAR>-<VAR>os</VAR>
</PRE>
<P>
See the file <TT>`config.sub'</TT> for the possible values of each field.
If <TT>`config.sub'</TT> isn't included in this package, then this package
doesn't need to know the machine type.
<P>
If you are <EM>building</EM> compiler tools for cross-compiling, you
should use the @option{--target=<VAR>type</VAR>} option to select the type of
system they will produce code for.
<P>
If you want to <EM>use</EM> a cross compiler, that generates code for a
platform different from the build platform, you should specify the
<EM>host</EM> platform (i.e., that on which the generated programs will
eventually be run) with @option{--host=<VAR>type</VAR>}.
<H2><A NAME="SEC142" HREF="autoconf_toc.html#TOC142">Sharing Defaults</A></H2>
<P>
If you want to set default values for @command{configure} scripts to
share, you can create a site shell script called <TT>`config.site'</TT> that
gives default values for variables like <CODE>CC</CODE>, <CODE>cache_file</CODE>,
and <CODE>prefix</CODE>. @command{configure} looks for
<TT>`<VAR>prefix</VAR>/share/config.site'</TT> if it exists, then
<TT>`<VAR>prefix</VAR>/etc/config.site'</TT> if it exists. Or, you can set the
<CODE>CONFIG_SITE</CODE> environment variable to the location of the site
script. A warning: not all @command{configure} scripts look for a site
script.
<H2><A NAME="SEC143" HREF="autoconf_toc.html#TOC143">Defining Variables</A></H2>
<P>
Variables not defined in a site shell script can be set in the
environment passed to @command{configure}. However, some packages may
run configure again during the build, and the customized values of these
variables may be lost. In order to avoid this problem, you should set
them in the @command{configure} command line, using <SAMP>`VAR=value'</SAMP>.
For example:
<PRE>
./configure CC=/usr/local2/bin/gcc
</PRE>
<P>
will cause the specified gcc to be used as the C compiler (unless it is
overridden in the site shell script).
<H2><A NAME="SEC144" HREF="autoconf_toc.html#TOC144">@command{configure} Invocation</A></H2>
<P>
@command{configure} recognizes the following options to control how it
operates.
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the options to @command{configure}, and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version of Autoconf used to generate the @command{configure}
script, and exit.
<DT>@option{--cache-file=<VAR>file</VAR>}
<DD>
<A NAME="IDX789"></A>
Enable the cache: use and save the results of the tests in <VAR>file</VAR>,
traditionally <TT>`config.cache'</TT>. <VAR>file</VAR> defaults to
<TT>`/dev/null'</TT> to disable caching.
<DT>@option{--config-cache}
<DD>
<DT>@option{-C}
<DD>
Alias for @option{--cache-file=config.cache}.
<DT>@option{--quiet}
<DD>
<DT>@option{--silent}
<DD>
<DT>@option{-q}
<DD>
Do not print messages saying which checks are being made. To suppress
all normal output, redirect it to <TT>`/dev/null'</TT> (any error messages
will still be shown).
<DT>@option{--srcdir=<VAR>dir</VAR>}
<DD>
Look for the package's source code in directory <VAR>dir</VAR>. Usually
@command{configure} can determine that directory automatically.
</DL>
<P>
@command{configure} also accepts some other, not widely useful, options.
Run <SAMP>`configure --help'</SAMP> for more details.
<H1><A NAME="SEC145" HREF="autoconf_toc.html#TOC145">Recreating a Configuration</A></H1>
<P>
<A NAME="IDX790"></A>
<P>
The @command{configure} script creates a file named <TT>`config.status'</TT>,
which actually configures, <EM>instantiates</EM>, the template files. It
also records the configuration options that were specified when the
package was last configured in case reconfiguring is needed.
<P>
Synopsis:
<PRE>
./config.status <VAR>option</VAR>... [<VAR>file</VAR>...]
</PRE>
<P>
It configures the <VAR>files</VAR>, if none are specified, all the templates
are instantiated. The files must be specified without their
dependencies, as in
<PRE>
./config.status foobar
</PRE>
<P>
not
<PRE>
./config.status foobar:foo.in:bar.in
</PRE>
<P>
The supported <VAR>option</VAR>s are:
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the command line options, the list of the template
files and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version number of Autoconf and exit.
<DT>@option{--debug}
<DD>
<DT>@option{-d}
<DD>
Don't remove the temporary files.
<DT>@option{--file=<VAR>file</VAR>[:<VAR>template</VAR>]}
<DD>
Require that <VAR>file</VAR> be instantiated as if
<SAMP>`AC_CONFIG_FILES(<VAR>file</VAR>:<VAR>template</VAR>)'</SAMP> was used. Both
<VAR>file</VAR> and <VAR>template</VAR> may be <SAMP>`-'</SAMP> in which case the standard
output and/or standard input, respectively, is used. If a
<VAR>template</VAR> filename is relative, it is first looked for in the build
tree, and then in the source tree. See section <A HREF="autoconf.html#SEC20">Taking Configuration Actions</A>, for
more details.
This option and the following ones provide one way for separately
distributed packages to share the values computed by @command{configure}.
Doing so can be useful if some of the packages need a superset of the
features that one of them, perhaps a common library, does. These
options allow a <TT>`config.status'</TT> file to create files other than the
ones that its <TT>`configure.ac'</TT> specifies, so it can be used for a
different package.
<DT>@option{--header=<VAR>file</VAR>[:<VAR>template</VAR>]}
<DD>
Same as @option{--file} above, but with <SAMP>`AC_CONFIG_HEADERS'</SAMP>.
<DT>@option{--recheck}
<DD>
Ask <TT>`config.status'</TT> to update itself and exit (no instantiation).
This option is useful if you change @command{configure}, so that the
results of some tests might be different from the previous run. The
@option{--recheck} option re-runs @command{configure} with the same arguments
you used before, plus the @option{--no-create} option, which prevents
@command{configure} from running <TT>`config.status'</TT> and creating
<TT>`Makefile'</TT> and other files, and the @option{--no-recursion} option,
which prevents @command{configure} from running other @command{configure}
scripts in subdirectories. (This is so other <TT>`Makefile'</TT> rules can
run <TT>`config.status'</TT> when it changes; see section <A HREF="autoconf.html#SEC26">Automatic Remaking</A>,
for an example).
</DL>
<P>
<TT>`config.status'</TT> checks several optional environment variables that
can alter its behavior:
<P>
<DL>
<DT><U>Variable:</U> <B>CONFIG_SHELL</B>
<DD><A NAME="IDX791"></A>
<A NAME="IDX792"></A>
The shell with which to run @command{configure} for the @option{--recheck}
option. It must be Bourne-compatible. The default is a shell that
supports @env{LINENO} if available, and <TT>`/bin/sh'</TT> otherwise.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>CONFIG_STATUS</B>
<DD><A NAME="IDX793"></A>
<A NAME="IDX794"></A>
The file name to use for the shell script that records the
configuration. The default is <TT>`./config.status'</TT>. This variable is
useful when one package uses parts of another and the @command{configure}
scripts shouldn't be merged because they are maintained separately.
</DL>
<P>
You can use <TT>`./config.status'</TT> in your Makefiles. For example, in
the dependencies given above (see section <A HREF="autoconf.html#SEC26">Automatic Remaking</A>),
<TT>`config.status'</TT> is run twice when <TT>`configure.ac'</TT> has changed.
If that bothers you, you can make each run only regenerate the files for
that rule:
<PRE>
config.h: stamp-h
stamp-h: config.h.in config.status
./config.status config.h
echo > stamp-h
Makefile: Makefile.in config.status
./config.status Makefile
</PRE>
<P>
The calling convention of <TT>`config.status'</TT> has changed, see
section <A HREF="autoconf.html#SEC147">Obsolete <TT>`config.status'</TT> Invocation</A>, for details.
<H1><A NAME="SEC146" HREF="autoconf_toc.html#TOC146">Obsolete Constructs</A></H1>
<P>
Autoconf changes, and throughout the years some constructs are obsoleted.
Most of the changes involve the macros, but the tools themselves, or
even some concepts, are now considered obsolete.
<P>
You may completely skip this chapter if you are new to Autoconf, its
intention is mainly to help maintainers updating their packages by
understanding how to move to more modern constructs.
<H2><A NAME="SEC147" HREF="autoconf_toc.html#TOC147">Obsolete <TT>`config.status'</TT> Invocation</A></H2>
<P>
<TT>`config.status'</TT> now supports arguments to specify the files to
instantiate, see section <A HREF="autoconf.html#SEC145">Recreating a Configuration</A>, for more details.
Before, environment variables had to be used.
<P>
<DL>
<DT><U>Variable:</U> <B>CONFIG_COMMANDS</B>
<DD><A NAME="IDX795"></A>
<A NAME="IDX796"></A>
The tags of the commands to execute. The default is the arguments given
to <CODE>AC_OUTPUT</CODE> and <CODE>AC_CONFIG_COMMANDS</CODE> in
<TT>`configure.ac'</TT>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>CONFIG_FILES</B>
<DD><A NAME="IDX797"></A>
<A NAME="IDX798"></A>
The files in which to perform <SAMP>`@<VAR>variable</VAR>@'</SAMP> substitutions.
The default is the arguments given to <CODE>AC_OUTPUT</CODE> and
<CODE>AC_CONFIG_FILES</CODE> in <TT>`configure.ac'</TT>.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>CONFIG_HEADERS</B>
<DD><A NAME="IDX799"></A>
<A NAME="IDX800"></A>
The files in which to substitute C <CODE>#define</CODE> statements. The
default is the arguments given to <CODE>AC_CONFIG_HEADERS</CODE>; if that
macro was not called, <TT>`config.status'</TT> ignores this variable.
</DL>
<P>
<DL>
<DT><U>Variable:</U> <B>CONFIG_LINKS</B>
<DD><A NAME="IDX801"></A>
<A NAME="IDX802"></A>
The symbolic links to establish. The default is the arguments given to
<CODE>AC_CONFIG_LINKS</CODE>; if that macro was not called,
<TT>`config.status'</TT> ignores this variable.
</DL>
<P>
In section <A HREF="autoconf.html#SEC145">Recreating a Configuration</A>, using this old interface, the example
would be:
<PRE>
config.h: stamp-h
stamp-h: config.h.in config.status
CONFIG_COMMANDS= CONFIG_LINKS= CONFIG_FILES= \
CONFIG_HEADERS=config.h ./config.status
echo > stamp-h
Makefile: Makefile.in config.status
CONFIG_COMMANDS= CONFIG_LINKS= CONFIG_HEADERS= \
CONFIG_FILES=Makefile ./config.status
</PRE>
<P>
(If <TT>`configure.ac'</TT> does not call <CODE>AC_CONFIG_HEADERS</CODE>, there is
no need to set @command{CONFIG_HEADERS} in the <CODE>make</CODE> rules, equally
for @command{CONFIG_COMMANDS} etc.)
<H2><A NAME="SEC148" HREF="autoconf_toc.html#TOC148"><TT>`acconfig.h'</TT></A></H2>
<P>
<A NAME="IDX803"></A>
<A NAME="IDX804"></A>
<A NAME="IDX805"></A>
<P>
In order to produce <TT>`config.h.in'</TT>, @command{autoheader} needs to
build or to find templates for each symbol. Modern releases of Autoconf
use <CODE>AH_VERBATIM</CODE> and <CODE>AH_TEMPLATE</CODE> (see section <A HREF="autoconf.html#SEC30">Autoheader Macros</A>), but in older releases a file, <TT>`acconfig.h'</TT>, contained the
list of needed templates. @command{autoheader} copies comments and
<CODE>#define</CODE> and <CODE>#undef</CODE> statements from <TT>`acconfig.h'</TT> in
the current directory, if present. This file used to be mandatory if
you <CODE>AC_DEFINE</CODE> any additional symbols.
<P>
Modern releases of Autoconf also provide <CODE>AH_TOP</CODE> and
<CODE>AH_BOTTOM</CODE> if you need to prepend/append some information to
<TT>`config.h.in'</TT>. Ancient versions of Autoconf had a similar feature:
if <TT>`./acconfig.h'</TT> contains the string <SAMP>`@TOP@'</SAMP>,
@command{autoheader} copies the lines before the line containing
<SAMP>`@TOP@'</SAMP> into the top of the file that it generates. Similarly,
if <TT>`./acconfig.h'</TT> contains the string <SAMP>`@BOTTOM@'</SAMP>,
@command{autoheader} copies the lines after that line to the end of the
file it generates. Either or both of those strings may be omitted. An
even older alternate way to produce the same effect in jurasik versions
of Autoconf is to create the files <TT>`<VAR>file</VAR>.top'</TT> (typically
<TT>`config.h.top'</TT>) and/or <TT>`<VAR>file</VAR>.bot'</TT> in the current
directory. If they exist, @command{autoheader} copies them to the
beginning and end, respectively, of its output.
<P>
In former versions of Autoconf, the files used in preparing a software
package for distribution were:
<PRE>
configure.ac --. .------> autoconf* -----> configure
+---+
[aclocal.m4] --+ `---.
[acsite.m4] ---' |
+--> [autoheader*] -> [config.h.in]
[acconfig.h] ----. |
+-----'
[config.h.top] --+
[config.h.bot] --'
</PRE>
<P>
Use only the <CODE>AH_</CODE> macros, <TT>`configure.ac'</TT> should be
self-contained, and should not depend upon <TT>`acconfig.h'</TT> etc.
<H2><A NAME="SEC149" HREF="autoconf_toc.html#TOC149">Using @command{autoupdate} to Modernize <TT>`configure.ac'</TT></A></H2>
<P>
<A NAME="IDX806"></A>
<P>
The @command{autoupdate} program updates a <TT>`configure.ac'</TT> file that
calls Autoconf macros by their old names to use the current macro names.
In version 2 of Autoconf, most of the macros were renamed to use a more
uniform and descriptive naming scheme. See section <A HREF="autoconf.html#SEC103">Macro Names</A>, for a
description of the new scheme. Although the old names still work
(see section <A HREF="autoconf.html#SEC150">Obsolete Macros</A>, for a list of the old macros and the corresponding
new names), you can make your <TT>`configure.ac'</TT> files more readable
and make it easier to use the current Autoconf documentation if you
update them to use the new macro names.
<P>
<A NAME="IDX807"></A>
If given no arguments, @command{autoupdate} updates <TT>`configure.ac'</TT>,
backing up the original version with the suffix <TT>`~'</TT> (or the value
of the environment variable <CODE>SIMPLE_BACKUP_SUFFIX</CODE>, if that is
set). If you give @command{autoupdate} an argument, it reads that file
instead of <TT>`configure.ac'</TT> and writes the updated file to the
standard output.
<P>
@command{autoupdate} accepts the following options:
<DL COMPACT>
<DT>@option{--help}
<DD>
<DT>@option{-h}
<DD>
Print a summary of the command line options and exit.
<DT>@option{--version}
<DD>
<DT>@option{-V}
<DD>
Print the version number of Autoconf and exit.
<DT>@option{--verbose}
<DD>
<DT>@option{-v}
<DD>
Report processing steps.
<DT>@option{--debug}
<DD>
<DT>@option{-d}
<DD>
Don't remove the temporary files.
<DT>@option{--force}
<DD>
<DT>@option{-f}
<DD>
Force the update even if the file has not changed. Disregard the cache.
<DT>@option{--include=<VAR>dir</VAR>}
<DD>
<DT>@option{-I <VAR>dir</VAR>}
<DD>
Also look for input files in <VAR>dir</VAR>. Multiple invocations accumulate.
Directories are browsed from last to first.
</DL>
<H2><A NAME="SEC150" HREF="autoconf_toc.html#TOC150">Obsolete Macros</A></H2>
<P>
Several macros are obsoleted in Autoconf, for various reasons (typically
they failed to quote properly, couldn't be extended for more recent
issues etc.). They are still supported, but deprecated: their use
should be avoided.
<P>
During the jump from Autoconf version 1 to version 2, most of the
macros were renamed to use a more uniform and descriptive naming scheme,
but their signature did not change. See section <A HREF="autoconf.html#SEC103">Macro Names</A>, for a
description of the new naming scheme. Below, there is just the mapping
from old names to new names for these macros, the reader is invited to
refer to the definition of the new macro for the signature and the
description.
<P>
<DL>
<DT><U>Macro:</U> <B>AC_ALLOCA</B>
<DD><A NAME="IDX808"></A>
<A NAME="IDX809"></A>
<CODE>AC_FUNC_ALLOCA</CODE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_ARG_ARRAY</B>
<DD><A NAME="IDX810"></A>
<A NAME="IDX811"></A>
removed because of limited usefulness
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_C_CROSS</B>
<DD><A NAME="IDX812"></A>
<A NAME="IDX813"></A>
This macro is obsolete; it does nothing.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CANONICAL_SYSTEM</B>
<DD><A NAME="IDX814"></A>
<A NAME="IDX815"></A>
Determine the system type and set output variables to the names of the
canonical system types. See section <A HREF="autoconf.html#SEC123">Getting the Canonical System Type</A>, for details about the
variables this macro sets.
<P>
The user is encouraged to use either <CODE>AC_CANONICAL_BUILD</CODE>, or
<CODE>AC_CANONICAL_HOST</CODE>, or <CODE>AC_CANONICAL_TARGET</CODE>, depending on
the needs. Using <CODE>AC_CANONICAL_TARGET</CODE> is enough to run the two
other macros.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHAR_UNSIGNED</B>
<DD><A NAME="IDX816"></A>
<A NAME="IDX817"></A>
<CODE>AC_C_CHAR_UNSIGNED</CODE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECK_TYPE</B> <I>(<VAR>type</VAR>, <VAR>default</VAR>)</I>
<DD><A NAME="IDX818"></A>
<A NAME="IDX819"></A>
Autoconf, up to 2.13, used to provide this version of
<CODE>AC_CHECK_TYPE</CODE>, deprecated because of its flaws. Firstly, although
it is a member of the <CODE>CHECK</CODE> clan, singular sub-family, it does
more than just checking. Second, missing types are not
<CODE>typedef</CODE>'d, they are <CODE>#define</CODE>'d, which can lead to
incompatible code in the case of pointer types.
<P>
This use of <CODE>AC_CHECK_TYPE</CODE> is obsolete and discouraged, see
section <A HREF="autoconf.html#SEC59">Generic Type Checks</A>, for the description of the current macro.
<P>
If the type <VAR>type</VAR> is not defined, define it to be the C (or C++)
builtin type <VAR>default</VAR>; e.g., <SAMP>`short'</SAMP> or <SAMP>`unsigned'</SAMP>.
<P>
This macro is equivalent to:
<PRE>
AC_CHECK_TYPE([<VAR>type</VAR>],
[AC_DEFINE([<VAR>type</VAR>], [<VAR>default</VAR>],
[Define to `<VAR>default</VAR>' if <sys/types.h>
does not define.])])
</PRE>
<P>
In order to keep backward compatibility, the two versions of
<CODE>AC_CHECK_TYPE</CODE> are implemented, selected by a simple heuristics:
<OL>
<LI>
If there are three or four arguments, the modern version is used.
<LI>
If the second argument appears to be a C or C++ type, then the
obsolete version is used. This happens if the argument is a C or C++
<EM>builtin</EM> type or a C identifier ending in <SAMP>`_t'</SAMP>, optionally
followed by one of <SAMP>`[(* '</SAMP> and then by a string of zero or more
characters taken from the set <SAMP>`[]()* _a-zA-Z0-9'</SAMP>.
<LI>
If the second argument is spelled with the alphabet of valid C and C++
types, the user is warned and the modern version is used.
<LI>
Otherwise, the modern version is used.
</OL>
<P>
You are encouraged either to use a valid builtin type, or to use the
equivalent modern code (see above), or better yet, to use
<CODE>AC_CHECK_TYPES</CODE> together with
<PRE>
#if !HAVE_LOFF_T
typedef loff_t off_t;
#endif
</PRE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CHECKING</B> <I>(<VAR>feature-description</VAR>)</I>
<DD><A NAME="IDX820"></A>
<A NAME="IDX821"></A>
Same as <SAMP>`AC_MSG_NOTICE([checking <VAR>feature-description</VAR>...]'</SAMP>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_COMPILE_CHECK</B> <I>(<VAR>echo-text</VAR>, <VAR>includes</VAR>, <VAR>function-body</VAR>, <VAR>action-if-found</VAR>, @ovar{action-if-not-found})</I>
<DD><A NAME="IDX822"></A>
<A NAME="IDX823"></A>
This is an obsolete version of <CODE>AC_TRY_LINK</CODE> (see section <A HREF="autoconf.html#SEC71">Examining Libraries</A>), with the addition that it prints <SAMP>`checking for
<VAR>echo-text</VAR>'</SAMP> to the standard output first, if <VAR>echo-text</VAR> is
non-empty. Use <CODE>AC_MSG_CHECKING</CODE> and <CODE>AC_MSG_RESULT</CODE> instead
to print messages (see section <A HREF="autoconf.html#SEC86">Printing Messages</A>).
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CONST</B>
<DD><A NAME="IDX824"></A>
<A NAME="IDX825"></A>
<CODE>AC_C_CONST</CODE>
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CROSS_CHECK</B>
<DD><A NAME="IDX826"></A>
<A NAME="IDX827"></A>
Same as <CODE>AC_C_CROSS</CODE>, which is obsolete too, and does nothing
<CODE>:-)</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_CYGWIN</B>
<DD><A NAME="IDX828"></A>
<A NAME="IDX829"></A>
Check for the Cygwin environment in which case the shell variable
<CODE>CYGWIN</CODE> is set to <SAMP>`yes'</SAMP>. Don't use this macro, the dignified
means to check the nature of the host is using
<CODE>AC_CANONICAL_HOST</CODE>. As a matter of fact this macro is defined as:
<PRE>
AC_REQUIRE([AC_CANONICAL_HOST])[]dnl
case $host_os in
*cygwin* ) CYGWIN=yes;;
* ) CYGWIN=no;;
esac
</PRE>
<P>
Beware that the variable <CODE>CYGWIN</CODE> has a very special meaning when
running CygWin32, and should not be changed. That's yet another reason
not to use this macro.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_DECL_YYTEXT</B>
<DD><A NAME="IDX830"></A>
<A NAME="IDX831"></A>
Does nothing, now integrated in <CODE>AC_PROG_LEX</CODE>.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AC_DIR_HEADER</B>
<DD><A NAME="IDX832"></A>
<A NAME="IDX833"></A>
<A NAME="IDX834"></A>
<A NAME="IDX835"></A>
<A NAME="IDX836"></A>
<A NAME="IDX837"></A>
Like calling <CODE>AC_FUNC_CLOSEDIR_VOID</CODE> and<CODE>AC_HEADER_DIRENT</CODE>,
but defines a different set of C preprocessor macros to indicate which
header file is found:
<LI>Header </TD><TD> Old Symbol </TD><TD> New Symbol
<LI><TT>`dirent.h'</TT> </TD><TD> <CODE>DIRENT</CODE> </TD><TD> <CODE>HAVE_DIRENT_H</CODE>
<LI><TT>`sys/ndir.h'</TT> </TD><TD> <CODE>SYSNDIR</CODE> </TD><TD> <CODE>HAVE_SYS_NDIR_H</CODE>
<LI><TT>`sys/dir.h'</TT> </TD><TD> <CODE>SYSDIR</CODE> </TD><TD> <CODE>HAVE_SYS_DIR_H</CODE>
<LI><TT>`ndir.h'</TT> </TD><TD> <CODE>NDIR</CODE> </TD><TD> <CODE>HAVE_NDIR_H</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_DYNIX_SEQ</B>
<DD><A NAME="IDX838"></A>
<A NAME="IDX839"></A>
If on Dynix/PTX (Sequent UNIX), add @option{-lseq} to output variable
<CODE>LIBS</CODE>. This macro used to be defined as
<PRE>
AC_CHECK_LIB(seq, getmntent, LIBS="-lseq $LIBS")
</PRE>
now it is just <CODE>AC_FUNC_GETMNTENT</CODE>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_EXEEXT</B>
<DD><A NAME="IDX840"></A>
<A NAME="IDX841"></A>
<A NAME="IDX842"></A>
Defined the output variable <CODE>EXEEXT</CODE> based on the output of the
compiler, which is now done automatically. Typically set to empty
string if Unix and <SAMP>`.exe'</SAMP> if Win32 or OS/2.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_EMXOS2</B>
<DD><A NAME="IDX843"></A>
<A NAME="IDX844"></A>
Similar to <CODE>AC_CYGWIN</CODE> but checks for the EMX environment on OS/2
and sets <CODE>EMXOS2</CODE>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_ERROR</B>
<DD><A NAME="IDX845"></A>
<A NAME="IDX846"></A>
<CODE>AC_MSG_ERROR</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_FIND_X</B>
<DD><A NAME="IDX847"></A>
<A NAME="IDX848"></A>
<CODE>AC_PATH_X</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_FIND_XTRA</B>
<DD><A NAME="IDX849"></A>
<A NAME="IDX850"></A>
<CODE>AC_PATH_XTRA</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_CHECK</B>
<DD><A NAME="IDX851"></A>
<A NAME="IDX852"></A>
<CODE>AC_CHECK_FUNC</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_FUNC_WAIT3</B>
<DD><A NAME="IDX853"></A>
<A NAME="IDX854"></A>
<A NAME="IDX855"></A>
If <CODE>wait3</CODE> is found and fills in the contents of its third argument
(a <SAMP>`struct rusage *'</SAMP>), which HP-UX does not do, define
<CODE>HAVE_WAIT3</CODE>.
These days portable programs should use <CODE>waitpid</CODE>, not
<CODE>wait3</CODE>, as <CODE>wait3</CODE> is being removed from the Open Group
standards, and will not appear in the next revision of POSIX.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_GCC_TRADITIONAL</B>
<DD><A NAME="IDX856"></A>
<A NAME="IDX857"></A>
<CODE>AC_PROG_GCC_TRADITIONAL</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_GETGROUPS_T</B>
<DD><A NAME="IDX858"></A>
<A NAME="IDX859"></A>
<CODE>AC_TYPE_GETGROUPS</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_GETLOADAVG</B>
<DD><A NAME="IDX860"></A>
<A NAME="IDX861"></A>
<CODE>AC_FUNC_GETLOADAVG</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HAVE_FUNCS</B>
<DD><A NAME="IDX862"></A>
<A NAME="IDX863"></A>
<CODE>AC_CHECK_FUNCS</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HAVE_HEADERS</B>
<DD><A NAME="IDX864"></A>
<A NAME="IDX865"></A>
<CODE>AC_CHECK_HEADERS</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HAVE_LIBRARY</B> <I>(<VAR>library</VAR>, @ovar{action-if-found}, @ovar{action-if-not-found}, @ovar{other-libraries})</I>
<DD><A NAME="IDX866"></A>
<A NAME="IDX867"></A>
This macro is equivalent to calling <CODE>AC_CHECK_LIB</CODE> with a
<VAR>function</VAR> argument of <CODE>main</CODE>. In addition, <VAR>library</VAR> can
be written as any of <SAMP>`foo'</SAMP>, @option{-lfoo}, or <SAMP>`libfoo.a'</SAMP>. In
all of those cases, the compiler is passed @option{-lfoo}. However,
<VAR>library</VAR> cannot be a shell variable; it must be a literal name.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HAVE_POUNDBANG</B>
<DD><A NAME="IDX868"></A>
<A NAME="IDX869"></A>
<CODE>AC_SYS_INTERPRETER</CODE> (different calling convention)
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_CHECK</B>
<DD><A NAME="IDX870"></A>
<A NAME="IDX871"></A>
<CODE>AC_CHECK_HEADER</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_HEADER_EGREP</B>
<DD><A NAME="IDX872"></A>
<A NAME="IDX873"></A>
<CODE>AC_EGREP_HEADER</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_INIT</B> <I>(<VAR>unique-file-in-source-dir</VAR>)</I>
<DD><A NAME="IDX874"></A>
<A NAME="IDX875"></A>
Formerly <CODE>AC_INIT</CODE> used to have a single argument, and was
equivalent to:
<PRE>
AC_INIT
AC_CONFIG_SRCDIR(<VAR>unique-file-in-source-dir</VAR>)
</PRE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_INLINE</B>
<DD><A NAME="IDX876"></A>
<A NAME="IDX877"></A>
<CODE>AC_C_INLINE</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_INT_16_BITS</B>
<DD><A NAME="IDX878"></A>
<A NAME="IDX879"></A>
<A NAME="IDX880"></A>
If the C type <CODE>int</CODE> is 16 bits wide, define <CODE>INT_16_BITS</CODE>.
Use <SAMP>`AC_CHECK_SIZEOF(int)'</SAMP> instead.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_IRIX_SUN</B>
<DD><A NAME="IDX881"></A>
<A NAME="IDX882"></A>
If on IRIX (Silicon Graphics UNIX), add @option{-lsun} to output
<CODE>LIBS</CODE>. If you were using it to get <CODE>getmntent</CODE>, use
<CODE>AC_FUNC_GETMNTENT</CODE> instead. If you used it for the NIS versions
of the password and group functions, use <SAMP>`AC_CHECK_LIB(sun,
getpwnam)'</SAMP>. Up to Autoconf 2.13, it used to be
<PRE>
AC_CHECK_LIB(sun, getmntent, LIBS="-lsun $LIBS")
</PRE>
now it is defined as
<PRE>
AC_FUNC_GETMNTENT
AC_CHECK_LIB(sun, getpwnam)
</PRE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LANG_C</B>
<DD><A NAME="IDX883"></A>
<A NAME="IDX884"></A>
Same as <SAMP>`AC_LANG(C)'</SAMP>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LANG_CPLUSPLUS</B>
<DD><A NAME="IDX885"></A>
<A NAME="IDX886"></A>
Same as <SAMP>`AC_LANG(C++)'</SAMP>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LANG_FORTRAN77</B>
<DD><A NAME="IDX887"></A>
<A NAME="IDX888"></A>
Same as <SAMP>`AC_LANG(Fortran 77)'</SAMP>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LANG_RESTORE</B>
<DD><A NAME="IDX889"></A>
<A NAME="IDX890"></A>
Select the <VAR>language</VAR> that is saved on the top of the stack, as set
by <CODE>AC_LANG_SAVE</CODE>, remove it from the stack, and call
<CODE>AC_LANG(<VAR>language</VAR>)</CODE>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LANG_SAVE</B>
<DD><A NAME="IDX891"></A>
<A NAME="IDX892"></A>
Remember the current language (as set by <CODE>AC_LANG</CODE>) on a stack.
The current language does not change. <CODE>AC_LANG_PUSH</CODE> is preferred.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LINK_FILES</B> <I>(<VAR>source</VAR>..., <VAR>dest</VAR>...)</I>
<DD><A NAME="IDX893"></A>
<A NAME="IDX894"></A>
This is an obsolete version of <CODE>AC_CONFIG_LINKS</CODE>. An updated
version of:
<PRE>
AC_LINK_FILES(config/$machine.h config/$obj_format.h,
host.h object.h)
</PRE>
is:
<PRE>
AC_CONFIG_LINKS(host.h:config/$machine.h
object.h:config/$obj_format.h)
</PRE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LN_S</B>
<DD><A NAME="IDX895"></A>
<A NAME="IDX896"></A>
<CODE>AC_PROG_LN_S</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LONG_64_BITS</B>
<DD><A NAME="IDX897"></A>
<A NAME="IDX898"></A>
<A NAME="IDX899"></A>
Define <CODE>LONG_64_BITS</CODE> if the C type <CODE>long int</CODE> is 64 bits wide.
Use the generic macro <SAMP>`AC_CHECK_SIZEOF([long int])'</SAMP> instead.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LONG_DOUBLE</B>
<DD><A NAME="IDX900"></A>
<A NAME="IDX901"></A>
<CODE>AC_C_LONG_DOUBLE</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_LONG_FILE_NAMES</B>
<DD><A NAME="IDX902"></A>
<A NAME="IDX903"></A>
<CODE>AC_SYS_LONG_FILE_NAMES</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_MAJOR_HEADER</B>
<DD><A NAME="IDX904"></A>
<A NAME="IDX905"></A>
<CODE>AC_HEADER_MAJOR</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_MEMORY_H</B>
<DD><A NAME="IDX906"></A>
<A NAME="IDX907"></A>
<A NAME="IDX908"></A>
Used to define <CODE>NEED_MEMORY_H</CODE> if the <CODE>mem</CODE> functions were
defined in <TT>`memory.h'</TT>. Today it is equivalent to
<SAMP>`AC_CHECK_HEADERS(memory.h)'</SAMP>. Adjust your code to depend upon
<CODE>HAVE_MEMORY_H</CODE>, not <CODE>NEED_MEMORY_H</CODE>, see See section <A HREF="autoconf.html#SEC37">Standard Symbols</A>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_MINGW32</B>
<DD><A NAME="IDX909"></A>
<A NAME="IDX910"></A>
Similar to <CODE>AC_CYGWIN</CODE> but checks for the MingW32 compiler
environment and sets <CODE>MINGW32</CODE>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_MINUS_C_MINUS_O</B>
<DD><A NAME="IDX911"></A>
<A NAME="IDX912"></A>
<CODE>AC_PROG_CC_C_O</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_MMAP</B>
<DD><A NAME="IDX913"></A>
<A NAME="IDX914"></A>
<CODE>AC_FUNC_MMAP</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_MODE_T</B>
<DD><A NAME="IDX915"></A>
<A NAME="IDX916"></A>
<CODE>AC_TYPE_MODE_T</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_OBJEXT</B>
<DD><A NAME="IDX917"></A>
<A NAME="IDX918"></A>
<A NAME="IDX919"></A>
Defined the output variable <CODE>OBJEXT</CODE> based on the output of the
compiler, after .c files have been excluded. Typically set to <SAMP>`o'</SAMP>
if Unix, <SAMP>`obj'</SAMP> if Win32. Now the compiler checking macros handle
this automatically.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_OBSOLETE</B> <I>(<VAR>this-macro-name</VAR>, @ovar{suggestion})</I>
<DD><A NAME="IDX920"></A>
<A NAME="IDX921"></A>
Make <CODE>m4</CODE> print a message to the standard error output warning that
<VAR>this-macro-name</VAR> is obsolete, and giving the file and line number
where it was called. <VAR>this-macro-name</VAR> should be the name of the
macro that is calling <CODE>AC_OBSOLETE</CODE>. If <VAR>suggestion</VAR> is given,
it is printed at the end of the warning message; for example, it can be
a suggestion for what to use instead of <VAR>this-macro-name</VAR>.
For instance
<PRE>
AC_OBSOLETE([$0], [; use AC_CHECK_HEADERS(unistd.h) instead])dnl
</PRE>
You are encouraged to use <CODE>AU_DEFUN</CODE> instead, since it gives better
services to the user.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_OFF_T</B>
<DD><A NAME="IDX922"></A>
<A NAME="IDX923"></A>
<CODE>AC_TYPE_OFF_T</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_OUTPUT</B> <I>(@ovar{file}..., @ovar{extra-cmds}, @ovar{init-cmds})</I>
<DD><A NAME="IDX924"></A>
<A NAME="IDX925"></A>
The use of <CODE>AC_OUTPUT</CODE> with argument is deprecated, this obsoleted
interface is equivalent to:
<PRE>
AC_CONFIG_FILES(<VAR>file</VAR>...)
AC_CONFIG_COMMANDS([default],
<VAR>extra-cmds</VAR>, <VAR>init-cmds</VAR>)
AC_OUTPUT
</PRE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_OUTPUT_COMMANDS</B> <I>(<VAR>extra-cmds</VAR>, @ovar{init-cmds})</I>
<DD><A NAME="IDX926"></A>
<A NAME="IDX927"></A>
Specify additional shell commands to run at the end of
<TT>`config.status'</TT>, and shell commands to initialize any variables
from @command{configure}. This macro may be called multiple times. It is
obsolete, replaced by <CODE>AC_CONFIG_COMMANDS</CODE>.
Here is an unrealistic example:
<PRE>
fubar=27
AC_OUTPUT_COMMANDS([echo this is extra $fubar, and so on.],
[fubar=$fubar])
AC_OUTPUT_COMMANDS([echo this is another, extra, bit],
[echo init bit])
</PRE>
Aside from the fact that <CODE>AC_CONFIG_COMMANDS</CODE> requires an
additional key, an important difference is that
<CODE>AC_OUTPUT_COMMANDS</CODE> is quoting its arguments twice, while
<CODE>AC_CONFIG_COMMANDS</CODE>. This means that <CODE>AC_CONFIG_COMMANDS</CODE>
can safely be given macro calls as arguments:
<PRE>
AC_CONFIG_COMMANDS(foo, [my_FOO()])
</PRE>
conversely, where one level of quoting was enough for literal strings
with <CODE>AC_OUTPUT_COMMANDS</CODE>, you need two with
<CODE>AC_CONFIG_COMMANDS</CODE>. The following lines are equivalent:
<PRE>
AC_OUTPUT_COMMANDS([echo "Square brackets: []"])
AC_CONFIG_COMMANDS([default], [[echo "Square brackets: []"]])
</PRE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_PID_T</B>
<DD><A NAME="IDX928"></A>
<A NAME="IDX929"></A>
<CODE>AC_TYPE_PID_T</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_PREFIX</B>
<DD><A NAME="IDX930"></A>
<A NAME="IDX931"></A>
<CODE>AC_PREFIX_PROGRAM</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_PROGRAMS_CHECK</B>
<DD><A NAME="IDX932"></A>
<A NAME="IDX933"></A>
<CODE>AC_CHECK_PROGS</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_PROGRAMS_PATH</B>
<DD><A NAME="IDX934"></A>
<A NAME="IDX935"></A>
<CODE>AC_PATH_PROGS</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_PROGRAM_CHECK</B>
<DD><A NAME="IDX936"></A>
<A NAME="IDX937"></A>
<CODE>AC_CHECK_PROG</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_PROGRAM_EGREP</B>
<DD><A NAME="IDX938"></A>
<A NAME="IDX939"></A>
<CODE>AC_EGREP_CPP</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_PROGRAM_PATH</B>
<DD><A NAME="IDX940"></A>
<A NAME="IDX941"></A>
<CODE>AC_PATH_PROG</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_REMOTE_TAPE</B>
<DD><A NAME="IDX942"></A>
<A NAME="IDX943"></A>
removed because of limited usefulness
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_RESTARTABLE_SYSCALLS</B>
<DD><A NAME="IDX944"></A>
<A NAME="IDX945"></A>
<CODE>AC_SYS_RESTARTABLE_SYSCALLS</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_RETSIGTYPE</B>
<DD><A NAME="IDX946"></A>
<A NAME="IDX947"></A>
<CODE>AC_TYPE_SIGNAL</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_RSH</B>
<DD><A NAME="IDX948"></A>
<A NAME="IDX949"></A>
Removed because of limited usefulness.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_SCO_INTL</B>
<DD><A NAME="IDX950"></A>
<A NAME="IDX951"></A>
<A NAME="IDX952"></A>
If on SCO UNIX, add @option{-lintl} to output variable <CODE>LIBS</CODE>. This
macro used to
<PRE>
AC_CHECK_LIB(intl, strftime, LIBS="-lintl $LIBS")
</PRE>
now it just calls <CODE>AC_FUNC_STRFTIME</CODE> instead.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_SETVBUF_REVERSED</B>
<DD><A NAME="IDX953"></A>
<A NAME="IDX954"></A>
<CODE>AC_FUNC_SETVBUF_REVERSED</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_SET_MAKE</B>
<DD><A NAME="IDX955"></A>
<A NAME="IDX956"></A>
<CODE>AC_PROG_MAKE_SET</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_SIZEOF_TYPE</B>
<DD><A NAME="IDX957"></A>
<A NAME="IDX958"></A>
<CODE>AC_CHECK_SIZEOF</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_SIZE_T</B>
<DD><A NAME="IDX959"></A>
<A NAME="IDX960"></A>
<CODE>AC_TYPE_SIZE_T</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_STAT_MACROS_BROKEN</B>
<DD><A NAME="IDX961"></A>
<A NAME="IDX962"></A>
<CODE>AC_HEADER_STAT</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_STDC_HEADERS</B>
<DD><A NAME="IDX963"></A>
<A NAME="IDX964"></A>
<CODE>AC_HEADER_STDC</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_STRCOLL</B>
<DD><A NAME="IDX965"></A>
<A NAME="IDX966"></A>
<CODE>AC_FUNC_STRCOLL</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_ST_BLKSIZE</B>
<DD><A NAME="IDX967"></A>
<A NAME="IDX968"></A>
<CODE>AC_STRUCT_ST_BLKSIZE</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_ST_BLOCKS</B>
<DD><A NAME="IDX969"></A>
<A NAME="IDX970"></A>
<CODE>AC_STRUCT_ST_BLOCKS</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_ST_RDEV</B>
<DD><A NAME="IDX971"></A>
<A NAME="IDX972"></A>
<CODE>AC_STRUCT_ST_RDEV</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_SYS_RESTARTABLE_SYSCALLS</B>
<DD><A NAME="IDX973"></A>
<A NAME="IDX974"></A>
<A NAME="IDX975"></A>
If the system automatically restarts a system call that is interrupted
by a signal, define <CODE>HAVE_RESTARTABLE_SYSCALLS</CODE>. This macro does
not check if system calls are restarted in general--it tests whether a
signal handler installed with <CODE>signal</CODE> (but not <CODE>sigaction</CODE>)
causes system calls to be restarted. It does not test if system calls
can be restarted when interrupted by signals that have no handler.
These days portable programs should use <CODE>sigaction</CODE> with
<CODE>SA_RESTART</CODE> if they want restartable system calls. They should
not rely on <CODE>HAVE_RESTARTABLE_SYSCALLS</CODE>, since nowadays whether a
system call is restartable is a dynamic issue, not a configuration-time
issue.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_SYS_SIGLIST_DECLARED</B>
<DD><A NAME="IDX976"></A>
<A NAME="IDX977"></A>
<CODE>AC_DECL_SYS_SIGLIST</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_TEST_CPP</B>
<DD><A NAME="IDX978"></A>
<A NAME="IDX979"></A>
<CODE>AC_TRY_CPP</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_TEST_PROGRAM</B>
<DD><A NAME="IDX980"></A>
<A NAME="IDX981"></A>
<CODE>AC_TRY_RUN</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_TIMEZONE</B>
<DD><A NAME="IDX982"></A>
<A NAME="IDX983"></A>
<CODE>AC_STRUCT_TIMEZONE</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_TIME_WITH_SYS_TIME</B>
<DD><A NAME="IDX984"></A>
<A NAME="IDX985"></A>
<CODE>AC_HEADER_TIME</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_UID_T</B>
<DD><A NAME="IDX986"></A>
<A NAME="IDX987"></A>
<CODE>AC_TYPE_UID_T</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_UNISTD_H</B>
<DD><A NAME="IDX988"></A>
<A NAME="IDX989"></A>
Same as <SAMP>`AC_CHECK_HEADERS(unistd.h)'</SAMP>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_USG</B>
<DD><A NAME="IDX990"></A>
<A NAME="IDX991"></A>
<A NAME="IDX992"></A>
Define <CODE>USG</CODE> if the BSD string functions are defined in
<TT>`strings.h'</TT>. You should no longer depend upon <CODE>USG</CODE>, but on
<CODE>HAVE_STRING_H</CODE>, see See section <A HREF="autoconf.html#SEC37">Standard Symbols</A>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_UTIME_NULL</B>
<DD><A NAME="IDX993"></A>
<A NAME="IDX994"></A>
<CODE>AC_FUNC_UTIME_NULL</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_VALIDATE_CACHED_SYSTEM_TUPLE</B> <I>(@ovar{cmd})</I>
<DD><A NAME="IDX995"></A>
<A NAME="IDX996"></A>
If the cache file is inconsistent with the current host, target and
build system types, it used to execute <VAR>cmd</VAR> or print a default
error message.
This is now handled by default.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_VERBOSE</B> <I>(<VAR>result-description</VAR>)</I>
<DD><A NAME="IDX997"></A>
<A NAME="IDX998"></A>
<CODE>AC_MSG_RESULT</CODE>.
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_VFORK</B>
<DD><A NAME="IDX999"></A>
<A NAME="IDX1000"></A>
<CODE>AC_FUNC_VFORK</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_VPRINTF</B>
<DD><A NAME="IDX1001"></A>
<A NAME="IDX1002"></A>
<CODE>AC_FUNC_VPRINTF</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_WAIT3</B>
<DD><A NAME="IDX1003"></A>
<A NAME="IDX1004"></A>
<CODE>AC_FUNC_WAIT3</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_WARN</B>
<DD><A NAME="IDX1005"></A>
<A NAME="IDX1006"></A>
<CODE>AC_MSG_WARN</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_WORDS_BIGENDIAN</B>
<DD><A NAME="IDX1007"></A>
<A NAME="IDX1008"></A>
<CODE>AC_C_BIGENDIAN</CODE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_XENIX_DIR</B>
<DD><A NAME="IDX1009"></A>
<A NAME="IDX1010"></A>
<A NAME="IDX1011"></A>
This macro used to add @option{-lx} to output variable <CODE>LIBS</CODE> if on
Xenix. Also, if <TT>`dirent.h'</TT> is being checked for, added
@option{-ldir} to <CODE>LIBS</CODE>. Now it is merely an alias of
<CODE>AC_HEADER_DIRENT</CODE> instead, plus some code to detect whether
running XENIX on which you should not depend:
<PRE>
AC_MSG_CHECKING([for Xenix])
AC_EGREP_CPP(yes,
[#if defined M_XENIX && !defined M_UNIX
yes
#endif],
[AC_MSG_RESULT([yes]); XENIX=yes],
[AC_MSG_RESULT([no]); XENIX=])
</PRE>
</DL>
<DL>
<DT><U>Macro:</U> <B>AC_YYTEXT_POINTER</B>
<DD><A NAME="IDX1012"></A>
<A NAME="IDX1013"></A>
<CODE>AC_DECL_YYTEXT</CODE>
</DL>
<H2><A NAME="SEC151" HREF="autoconf_toc.html#TOC151">Upgrading From Version 1</A></H2>
<P>
Autoconf version 2 is mostly backward compatible with version 1.
However, it introduces better ways to do some things, and doesn't
support some of the ugly things in version 1. So, depending on how
sophisticated your <TT>`configure.ac'</TT> files are, you might have to do
some manual work in order to upgrade to version 2. This chapter points
out some problems to watch for when upgrading. Also, perhaps your
@command{configure} scripts could benefit from some of the new features in
version 2; the changes are summarized in the file <TT>`NEWS'</TT> in the
Autoconf distribution.
<H3><A NAME="SEC152" HREF="autoconf_toc.html#TOC152">Changed File Names</A></H3>
<P>
If you have an <TT>`aclocal.m4'</TT> installed with Autoconf (as opposed to
in a particular package's source directory), you must rename it to
<TT>`acsite.m4'</TT>. See section <A HREF="autoconf.html#SEC13">Using @command{autoconf} to Create @command{configure}</A>.
<P>
If you distribute <TT>`install.sh'</TT> with your package, rename it to
<TT>`install-sh'</TT> so <CODE>make</CODE> builtin rules won't inadvertently
create a file called <TT>`install'</TT> from it. <CODE>AC_PROG_INSTALL</CODE>
looks for the script under both names, but it is best to use the new name.
<P>
If you were using <TT>`config.h.top'</TT>, <TT>`config.h.bot'</TT>, or
<TT>`acconfig.h'</TT>, you still can, but you will have less clutter if you
use the <CODE>AH_</CODE> macros. See section <A HREF="autoconf.html#SEC30">Autoheader Macros</A>.
<H3><A NAME="SEC153" HREF="autoconf_toc.html#TOC153">Changed Makefiles</A></H3>
<P>
Add <SAMP>`@CFLAGS@'</SAMP>, <SAMP>`@CPPFLAGS@'</SAMP>, and <SAMP>`@LDFLAGS@'</SAMP> in
your <TT>`Makefile.in'</TT> files, so they can take advantage of the values
of those variables in the environment when @command{configure} is run.
Doing this isn't necessary, but it's a convenience for users.
<P>
Also add <SAMP>`@configure_input@'</SAMP> in a comment to each input file for
<CODE>AC_OUTPUT</CODE>, so that the output files will contain a comment saying
they were produced by @command{configure}. Automatically selecting the
right comment syntax for all the kinds of files that people call
<CODE>AC_OUTPUT</CODE> on became too much work.
<P>
Add <TT>`config.log'</TT> and <TT>`config.cache'</TT> to the list of files you
remove in <CODE>distclean</CODE> targets.
<P>
If you have the following in <TT>`Makefile.in'</TT>:
<PRE>
prefix = /usr/local
exec_prefix = $(prefix)
</PRE>
<P>
you must change it to:
<PRE>
prefix = @prefix@
exec_prefix = @exec_prefix@
</PRE>
<P>
The old behavior of replacing those variables without <SAMP>`@'</SAMP>
characters around them has been removed.
<H3><A NAME="SEC154" HREF="autoconf_toc.html#TOC154">Changed Macros</A></H3>
<P>
Many of the macros were renamed in Autoconf version 2. You can still
use the old names, but the new ones are clearer, and it's easier to find
the documentation for them. See section <A HREF="autoconf.html#SEC150">Obsolete Macros</A>, for a table showing the
new names for the old macros. Use the @command{autoupdate} program to
convert your <TT>`configure.ac'</TT> to using the new macro names.
See section <A HREF="autoconf.html#SEC149">Using @command{autoupdate} to Modernize @file{configure.ac}</A>.
<P>
Some macros have been superseded by similar ones that do the job better,
but are not call-compatible. If you get warnings about calling obsolete
macros while running @command{autoconf}, you may safely ignore them, but
your @command{configure} script will generally work better if you follow
the advice it prints about what to replace the obsolete macros with. In
particular, the mechanism for reporting the results of tests has
changed. If you were using <CODE>echo</CODE> or <CODE>AC_VERBOSE</CODE> (perhaps
via <CODE>AC_COMPILE_CHECK</CODE>), your @command{configure} script's output will
look better if you switch to <CODE>AC_MSG_CHECKING</CODE> and
<CODE>AC_MSG_RESULT</CODE>. See section <A HREF="autoconf.html#SEC86">Printing Messages</A>. Those macros work best
in conjunction with cache variables. See section <A HREF="autoconf.html#SEC82">Caching Results</A>.
<H3><A NAME="SEC155" HREF="autoconf_toc.html#TOC155">Changed Results</A></H3>
<P>
If you were checking the results of previous tests by examining the
shell variable <CODE>DEFS</CODE>, you need to switch to checking the values of
the cache variables for those tests. <CODE>DEFS</CODE> no longer exists while
@command{configure} is running; it is only created when generating output
files. This difference from version 1 is because properly quoting the
contents of that variable turned out to be too cumbersome and
inefficient to do every time <CODE>AC_DEFINE</CODE> is called. See section <A HREF="autoconf.html#SEC83">Cache Variable Names</A>.
<P>
For example, here is a <TT>`configure.ac'</TT> fragment written for Autoconf
version 1:
<PRE>
AC_HAVE_FUNCS(syslog)
case "$DEFS" in
*-DHAVE_SYSLOG*) ;;
*) # syslog is not in the default libraries. See if it's in some other.
saved_LIBS="$LIBS"
for lib in bsd socket inet; do
AC_CHECKING(for syslog in -l$lib)
LIBS="$saved_LIBS -l$lib"
AC_HAVE_FUNCS(syslog)
case "$DEFS" in
*-DHAVE_SYSLOG*) break ;;
*) ;;
esac
LIBS="$saved_LIBS"
done ;;
esac
</PRE>
<P>
Here is a way to write it for version 2:
<PRE>
AC_CHECK_FUNCS(syslog)
if test $ac_cv_func_syslog = no; then
# syslog is not in the default libraries. See if it's in some other.
for lib in bsd socket inet; do
AC_CHECK_LIB($lib, syslog, [AC_DEFINE(HAVE_SYSLOG)
LIBS="$LIBS -l$lib"; break])
done
fi
</PRE>
<P>
If you were working around bugs in <CODE>AC_DEFINE_UNQUOTED</CODE> by adding
backslashes before quotes, you need to remove them. It now works
predictably, and does not treat quotes (except back quotes) specially.
See section <A HREF="autoconf.html#SEC81">Setting Output Variables</A>.
<P>
All of the boolean shell variables set by Autoconf macros now use
<SAMP>`yes'</SAMP> for the true value. Most of them use <SAMP>`no'</SAMP> for false,
though for backward compatibility some use the empty string instead. If
you were relying on a shell variable being set to something like 1 or
<SAMP>`t'</SAMP> for true, you need to change your tests.
<H3><A NAME="SEC156" HREF="autoconf_toc.html#TOC156">Changed Macro Writing</A></H3>
<P>
When defining your own macros, you should now use <CODE>AC_DEFUN</CODE>
instead of <CODE>define</CODE>. <CODE>AC_DEFUN</CODE> automatically calls
<CODE>AC_PROVIDE</CODE> and ensures that macros called via <CODE>AC_REQUIRE</CODE>
do not interrupt other macros, to prevent nested <SAMP>`checking...'</SAMP>
messages on the screen. There's no actual harm in continuing to use the
older way, but it's less convenient and attractive. See section <A HREF="autoconf.html#SEC102">Macro Definitions</A>.
<P>
You probably looked at the macros that came with Autoconf as a guide for
how to do things. It would be a good idea to take a look at the new
versions of them, as the style is somewhat improved and they take
advantage of some new features.
<P>
If you were doing tricky things with undocumented Autoconf internals
(macros, variables, diversions), check whether you need to change
anything to account for changes that have been made. Perhaps you can
even use an officially supported technique in version 2 instead of
kludging. Or perhaps not.
<P>
To speed up your locally written feature tests, add caching to them.
See whether any of your tests are of general enough usefulness to
encapsulate into macros that you can share.
<H2><A NAME="SEC157" HREF="autoconf_toc.html#TOC157">Upgrading From Version 2.13</A></H2>
<P>
The introduction of the previous section (see section <A HREF="autoconf.html#SEC151">Upgrading From Version 1</A>) perfectly
suits this section...
<BLOCKQUOTE>
<P>
Autoconf version 2.50 is mostly backward compatible with version 2.13.
However, it introduces better ways to do some things, and doesn't
support some of the ugly things in version 2.13. So, depending on how
sophisticated your <TT>`configure.ac'</TT> files are, you might have to do
some manual work in order to upgrade to version 2.50. This chapter
points out some problems to watch for when upgrading. Also, perhaps
your @command{configure} scripts could benefit from some of the new
features in version 2.50; the changes are summarized in the file
<TT>`NEWS'</TT> in the Autoconf distribution.
</BLOCKQUOTE>
<H3><A NAME="SEC158" HREF="autoconf_toc.html#TOC158">Changed Quotation</A></H3>
<P>
The most important changes are invisible to you: the implementation of
most macros have completely changed. This allowed more factorization of
the code, better error messages, a higher uniformity of the user's
interface etc. Unfortunately, as a side effect, some construct which
used to (miraculously) work might break starting with Autoconf 2.50.
The most common culprit is bad quotation.
<P>
For instance, in the following example, the message is not properly
quoted:
<PRE>
AC_INIT
AC_CHECK_HEADERS(foo.h,,
AC_MSG_ERROR(cannot find foo.h, bailing out))
AC_OUTPUT
</PRE>
<P>
Autoconf 2.13 simply ignores it:
<PRE>
$ <KBD>autoconf-2.13; ./configure --silent</KBD>
creating cache ./config.cache
configure: error: cannot find foo.h
$
</PRE>
<P>
while Autoconf 2.50 will produce a broken <TT>`configure'</TT>:
<PRE>
$ <KBD>autoconf-2.50; ./configure --silent</KBD>
configure: error: cannot find foo.h
./configure: exit: bad non-numeric arg `bailing'
./configure: exit: bad non-numeric arg `bailing'
$
</PRE>
<P>
The message needs to be quoted, and the <CODE>AC_MSG_ERROR</CODE> invocation
too!
<PRE>
AC_INIT
AC_CHECK_HEADERS(foo.h,,
[AC_MSG_ERROR([cannot find foo.h, bailing out])])
AC_OUTPUT
</PRE>
<P>
Many many (and many more) Autoconf macros were lacking proper quotation,
including no less than... <CODE>AC_DEFUN</CODE> itself!
<PRE>
$ <KBD>cat configure.in</KBD>
AC_DEFUN([AC_PROG_INSTALL],
[# My own much better version
])
AC_INIT
AC_PROG_INSTALL
AC_OUTPUT
$ <KBD>autoconf-2.13</KBD>
autoconf: Undefined macros:
***BUG in Autoconf--please report*** AC_FD_MSG
***BUG in Autoconf--please report*** AC_EPI
configure.in:1:AC_DEFUN([AC_PROG_INSTALL],
configure.in:5:AC_PROG_INSTALL
$ <KBD>autoconf-2.50</KBD>
$
</PRE>
<H3><A NAME="SEC159" HREF="autoconf_toc.html#TOC159">New Macros</A></H3>
<P>
<A NAME="IDX1014"></A>
<P>
Because Autoconf has been dormant for years, Automake provided
Autoconf-like macros for a while. Autoconf 2.50 now provides better
versions of these macros, integrated in the <CODE>AC_</CODE> namespace,
instead of <CODE>AM_</CODE>. But in order to ease the upgrading via
@command{autoupdate}, bindings to such <CODE>AM_</CODE> macros are provided.
<P>
Unfortunately Automake did not quote the name of these macros!
Therefore, when @command{m4} finds something like
<SAMP>`AC_DEFUN(AM_TYPE_PTRDIFF_T, ...)'</SAMP> in <TT>`aclocal.m4'</TT>,
<CODE>AM_TYPE_PTRDIFF_T</CODE> is
expanded, replaced with its Autoconf definition.
<P>
Fortunately Autoconf catches pre-<CODE>AC_INIT</CODE> expansions, and will
complain, in its own words:
<PRE>
$ <KBD>cat configure.in</KBD>
AC_INIT
AM_TYPE_PTRDIFF_T
$ <KBD>aclocal-1.4</KBD>
$ <KBD>autoconf</KBD>
./aclocal.m4:17: error: m4_defn: undefined macro: _m4_divert_diversion
actypes.m4:289: AM_TYPE_PTRDIFF_T is expanded from...
./aclocal.m4:17: the top level
$
</PRE>
<P>
Future versions of Automake will simply no longer define most of these
macros, and will properly quote the names of the remaining macros.
But you don't have to wait for it to happen to do the right thing right
now: do not depend upon macros from Automake as it is simply not its job
to provide macros (but the one it requires by itself):
<PRE>
$ <KBD>cat configure.in</KBD>
AC_INIT
AM_TYPE_PTRDIFF_T
$ <KBD>rm aclocal.m4</KBD>
$ <KBD>autoupdate</KBD>
autoupdate: `configure.in' is updated
$ <KBD>cat configure.in</KBD>
AC_INIT
AC_CHECK_TYPES([ptrdiff_t])
$ <KBD>aclocal-1.4</KBD>
$ <KBD>autoconf</KBD>
$
</PRE>
<H3><A NAME="SEC160" HREF="autoconf_toc.html#TOC160">Hosts and Cross-Compilation</A></H3>
<P>
Based on the experience of compiler writers, and after long public
debates, many aspects of the cross-compilation chain have changed:
<UL>
<LI>
the relationship between the build, host, and target architecture types,
<LI>
the command line interface for specifying them to @command{configure},
<LI>
the variables defined in @command{configure},
<LI>
the enabling of cross-compilation mode.
</UL>
<P>
The relationship between build, host, and target have been cleaned up:
the chain of default is now simply: target defaults to host, host to
build, and build to the result of @command{config.guess}. Nevertheless,
in order to ease the transition from 2.13 to 2.50, the following
transition scheme is implemented. <EM>Do not rely on it</EM>, as it will
be completely disabled in a couple of releases (we cannot keep it, as it
proves to cause more problems than to cure).
<P>
They all default to the result of running @command{config.guess}, unless
you specify either @option{--build} or @option{--host}. In this case,
the default becomes the system type you specified. If you specify both,
and they're different, @command{configure} will enter cross compilation
mode, so it won't run any tests that require execution.
<P>
Hint: if you mean to override the result of @command{config.guess},
prefer @option{--build} over @option{--host}. In the future,
@option{--host} will not override the name of the build system type.
Whenever you specify <CODE>--host</CODE>, be sure to specify <CODE>--build</CODE>
too.
<P>
For backward compatibility, @command{configure} will accept a system
type as an option by itself. Such an option will override the defaults
for build, host and target system types. The following configure
statement will configure a cross toolchain that will run on NetBSD/alpha
but generate code for GNU Hurd/sparc, which is also the build platform.
<PRE>
./configure --host=alpha-netbsd sparc-gnu
</PRE>
<P>
In Autoconf, the variables <CODE>build</CODE>, <CODE>host</CODE>, and <CODE>target</CODE>
had a different semantics before and after the invocation of
<CODE>AC_CANONICAL_BUILD</CODE> etc. Now, the argument of @option{--build} is
strictly copied into <CODE>build_alias</CODE>, and is left empty otherwise.
After the <CODE>AC_CANONICAL_BUILD</CODE>, <CODE>build</CODE> is set to the
canonicalized build type. To ease the transition, before, its contents
is the same as that of <CODE>build_alias</CODE>. Do <EM>not</EM> rely on this
broken feature.
<P>
For consistency with the backward compatibility scheme exposed above,
when @option{--host} is specified by @option{--build} isn't, the build
system will be assumed to be the same as @option{--host}, and
<SAMP>`build_alias'</SAMP> will be set to that value. Eventually, this
historically incorrect behavior will go away.
<P>
The former scheme to enable cross-compilation proved to cause more harm
than good, in particular, it used to be triggered too easily, leaving
regular end users puzzled in front of cryptic error messages.
@command{configure} could even enter cross-compilation mode, only
because the compiler was not functional. This is mainly because
@command{configure} used to try to detect cross-compilation, instead of
waiting for an explicit flag from the user.
<P>
Now, @command{configure} enters cross-compilation mode iff
@option{--host} is passed.
<P>
That's the short documentation. To ease the transition between 2.13 and
its successors, a more complicated scheme is implemented. <EM>Do not
rely on the following</EM>, as it will be removed in a near future.
<P>
If you specify @option{--host}, but not @option{--build}, when
@command{configure} performs the first compiler test it will try to run
an executable produced by the compiler. If the execution fails, it will
enter cross-compilation mode. This is fragile. Moreover, by the time
the compiler test is performed, it may be too late to modify the
build-system type: other tests may have already been performed.
Therefore, whenever you specify <CODE>--host</CODE>, be sure to specify
<CODE>--build</CODE> too.
<PRE>
./configure --build=i686-pc-linux-gnu --host=m68k-coff
</PRE>
<P>
will enter cross-compilation mode. The former interface, which
consisted in setting the compiler to a cross-compiler without informing
@command{configure} is obsolete. For instance, @command{configure} will
fail if it can't run the code generated by the specified compiler if you
configure as follows:
<PRE>
./configure CC=m68k-coff-gcc
</PRE>
<H3><A NAME="SEC161" HREF="autoconf_toc.html#TOC161"><CODE>AC_LIBOBJ</CODE> vs. <CODE>LIBOBJS</CODE></A></H3>
<P>
Up to Autoconf 2.13, the replacement of functions was triggered via the
variable <CODE>LIBOBJS</CODE>. Since Autoconf 2.50, the macro
<CODE>AC_LIBOBJ</CODE> should be used instead (see section <A HREF="autoconf.html#SEC47">Generic Function Checks</A>).
Starting at Autoconf 2.53, the use of <CODE>LIBOBJS</CODE> is an error.
<P>
This change is mandated by the unification of the GNU Build System
components. In particular, the various fragile techniques used to parse
a <TT>`configure.ac'</TT> are all replaced with the use of traces. As a
consequence, any action must be traceable, which obsoletes critical
variable assignments. Fortunately, <CODE>LIBOBJS</CODE> was the only problem.
<P>
At the time this documentation is written, Automake does not rely on
traces yet, but this is planed for a near future. Nevertheless, to
ease the transition, and to guarantee this future Automake release will
be able to use Autoconf 2.53, using <CODE>LIBOBJS</CODE> directly will make
@command{autoconf} fail. But note that the output, @command{configure},
is correct and fully functional: you have some delay to adjust your
source.
<P>
There are two typical uses of <CODE>LIBOBJS</CODE>: asking for a replacement
function, and adjusting <CODE>LIBOBJS</CODE> for Automake and/or Libtool.
<P>
As for function replacement, the fix is immediate: use
<CODE>AC_LIBOBJ</CODE>. For instance:
<PRE>
LIBOBJS="$LIBOBJS fnmatch.o"
LIBOBJS="$LIBOBJS malloc.$ac_objext"
</PRE>
<P>
should be replaced with:
<PRE>
AC_LIBOBJ([fnmatch])
AC_LIBOBJ([malloc])
</PRE>
<P>
When asked for automatic de-ANSI-fication, Automake needs
<CODE>LIBOBJS</CODE>'ed filenames to have <SAMP>`$U'</SAMP> appended to the
base names. Libtool requires the definition of <CODE>LTLIBOBJS</CODE>, which
suffixes are mapped to <SAMP>`.lo'</SAMP>. Although Autoconf provides them with
means to free the user to do that by herself, by the time of this
writing, none do. Therefore, it is common to see <TT>`configure.ac'</TT>
end with:
<PRE>
# This is necessary so that .o files in LIBOBJS are also built via
# the ANSI2KNR-filtering rules.
LIBOBJS=`echo "$LIBOBJS" | sed 's/\.o /\$U.o /g;s/\.o$/\$U.o/'`
LTLIBOBJS=`echo "$LIBOBJS" | sed 's/\.o/\.lo/g'`
AC_SUBST(LTLIBOBJS)
</PRE>
<P>
First, note that this code is <EM>wrong</EM>, because <SAMP>`.o'</SAMP> is not the
only possible extension<A NAME="DOCF4" HREF="autoconf_foot.html#FOOT4">(4)</A>! Because the token <CODE>LIBOBJS</CODE> is now
forbidden, you will have to replace this snippet with:
<PRE>
# This is necessary so that .o files in LIBOBJS are also built via
# the ANSI2KNR-filtering rules.
LIB@&t@OBJS=`echo "$LIB@&t@OBJS" |
sed 's,\.[[^.]]* ,$U&,g;s,\.[[^.]]*$,$U&,'`
LTLIBOBJS=`echo "$LIB@&t@OBJS" |
sed 's,\.[[^.]]* ,.lo ,g;s,\.[[^.]]*$,.lo,'`
AC_SUBST(LTLIBOBJS)
</PRE>
<P>
Unfortunately, @command{autoupdate} cannot help here, since... this is
not a macro! Of course, first make sure your release of Automake and/or
Libtool still requires these.
<H1><A NAME="SEC162" HREF="autoconf_toc.html#TOC162">Generating Test Suites with Autotest</A></H1>
<P>
<A NAME="IDX1015"></A>
<PRE>
<STRONG>Note: This section describes an experimental feature which will
be part of Autoconf in a forthcoming release. Although we believe
Autotest is stabilizing, this documentation describes an interface which
might change in the future: do not depend upon Autotest without
subscribing to the Autoconf mailing lists.</STRONG>
</PRE>
<P>
It is paradoxical that portable projects depend on nonportable tools to
run their test suite. Autoconf by itself is the paragon of this
problem: although it aims at perfectly portability, up to 2.13, its test
suite was using DejaGNU, a rich and complex testing framework, but which
is far from being standard on Unix systems. Worse yet, it was likely to
be missing on the most fragile platforms, the very platforms that are
most likely to torture Autoconf and exhibit deficiencies.
<P>
To circumvent this problem many package maintainers have developed their
own testing framework, based on simple shell scripts whose sole output
are their exit status: the test succeeded, or failed. In addition, most
of these tests share some common patterns, what results in lots of
duplicated code, tedious maintenance etc.
<P>
Following exactly the same reasoning that yielded to the inception of
Autoconf, Autotest provides a test suite generation frame work, based on
M4 macros, building a portable shell script. The suite itself is
equipped with automatic logging and tracing facilities which greatly
diminish the interaction with bug reporters, and simple timing reports.
<P>
Autoconf itself has been using Autotest for years, and we do attest that
it has considerably improved the strength of the test suite, and the
quality of bug reports. Other projects are known to use some generation
of Autotest, such as Bison, Free Recode, Free Wdiff, GNU Tar, each of
them having different needs, what slowly polishes Autotest as a general
testing framework.
<P>
Nonetheless, compared to DejaGNU, Autotest is inadequate for interactive
tool testing, which is probably its main limitation.
<H2><A NAME="SEC163" HREF="autoconf_toc.html#TOC163">Using an Autotest Test Suite</A></H2>
<H3><A NAME="SEC164" HREF="autoconf_toc.html#TOC164">@command{testsuite} Scripts</A></H3>
<P>
<A NAME="IDX1016"></A>
<P>
Generating testing or validation suites using Autotest is rather easy.
The whole validation suite is held in a file to be processed through
@command{autom4te}, itself using GNU <CODE>m4</CODE> under the scene, to
produce a stand-alone Bourne shell script which then gets distributed.
Neither @command{autom4te} nor GNU <CODE>m4</CODE> are not needed anymore at
the installer end.
<P>
<A NAME="IDX1017"></A>
Each test of the validation suite should be part of some test group. A
<EM>test group</EM> is a sequence of interwoven tests that ought to be
executed together, usually because one test in the group creates data
files than a later test in the same group needs to read. Complex test
groups make later debugging more tedious. It is much better keeping
keep only a few tests per test group, and if you can put only one test
per test group, this is just ideal.
<P>
For all but the simplest packages, some file such as <TT>`testsuite.at'</TT>
does not fully hold all test sources, as these are often easier to
maintain in separate files. Each of these separate files holds a single
test group, or a sequence of test groups all addressing some common
functionality in the package. In such cases, file <TT>`testsuite.at'</TT>
only initializes the whole validation suite, and sometimes do elementary
health checking, before listing include statements for all other test
files. The special file <TT>`package.m4'</TT>, containing the
identification of the package, is automatically included if found.
<P>
The validation scripts that Autotest produces are by convention called
@command{testsuite}. When run, @command{testsuite} executes each test
group in turn, producing only one summary line per test to say if that
particular test succeeded or failed. At end of all tests, summarizing
counters get printed. If any test failed, one debugging script gets
automatically generated for each test group which failed. These
debugging scripts are named <TT>`testsuite.<VAR>nn</VAR>'</TT>, where <VAR>nn</VAR> is
the sequence number of the test group. In the ideal situation, none of
the tests fail, and consequently, no debugging script is generated out
of validation.
<P>
The automatic generation of debugging scripts for failed test has the
purpose of easing the chase for bugs.
<P>
It often happens in practice that individual tests in the validation
suite need to get information coming out of the configuration process.
Some of this information, common for all validation suites, is provided
through the file <TT>`atconfig'</TT>, automatically created by
<CODE>AC_CONFIG_TESTDIR</CODE>. For configuration informations which your
testing environment specifically needs, you might prepare an optional
file named <TT>`atlocal.in'</TT>, instantiated by <CODE>AC_CONFIG_FILES</CODE>.
The configuration process produces <TT>`atconfig'</TT> and <TT>`atlocal'</TT>
out of these two input files, and these two produced files are
automatically read by the <TT>`testsuite'</TT> script.
<P>
Here is a diagram showing the relationship between files.
<P>
Files used in preparing a software package for distribution:
<PRE>
subfile-1.at ->.
... \
subfile-i.at ---->-- testsuite.at -->.
... / \
subfile-n.at ->' >-- autom4te* -->testsuite
/
[package.m4] ->'
</PRE>
<P>
Files used in configuring a software package:
<PRE>
.--> atconfig
/
[atlocal.in] --> config.status* --<
\
`--> [atlocal]
</PRE>
<P>
Files created during the test suite execution:
<PRE>
atconfig -->. .--> testsuite.log
\ /
>-- testsuite* --<
/ \
[atlocal] ->' `--> [testsuite.<VAR>nn</VAR>*]
</PRE>
<H3><A NAME="SEC165" HREF="autoconf_toc.html#TOC165">Autotest Logs</A></H3>
<P>
When run, the test suite creates a log file named after itself, e.g., a
test suite named @command{testsuite} creates <TT>`testsuite.log'</TT>. It
contains a lot of information, usually more than maintainers actually
need, but therefore most of the time it contains all that is needed:
<DL COMPACT>
<DT>command line arguments
<DD>
A very bad Unix habit which is unfortunately wide spread consists of
setting environment variables before the command, such as in
<SAMP>`CC=my-home-grown-cc ./testsuite'</SAMP>. This results in the test suite
not knowing this change, hence (i) it can't report it to you, and (ii)
it cannot preserve the value of <CODE>CC</CODE> for subsequent runs<A NAME="DOCF5" HREF="autoconf_foot.html#FOOT5">(5)</A>. Autoconf faced exactly the same problem, and solved it by asking
users to pass the variable definitions as command line arguments.
Autotest requires this rule too, but has no means to enforce it; the log
then contains a trace of the variables the user changed.
<DT><TT>`ChangeLog'</TT> excerpts
<DD>
The topmost lines of all the <TT>`ChangeLog'</TT>s found in the source
hierarchy. This is especially useful when bugs are reported against
development versions of the package, since the version string does not
provide sufficient information to know the exact state of the sources
the user compiled. Of course this relies on the use of a
<TT>`ChangeLog'</TT>.
<DT>build machine
<DD>
Running a test suite in a cross-compile environment is not an easy task,
since it would mean having the test suite run on a machine <VAR>build</VAR>,
while running programs on a machine <VAR>host</VAR>. It is much simpler to
run both the test suite and the programs on <VAR>host</VAR>, but then, from
the point of view of the test suite, there remains a single environment,
<VAR>host</VAR> = <VAR>build</VAR>. The log contains relevant information on the
state of the build machine, including some important environment
variables.
<DT>tested programs
<DD>
The absolute path and answers to @option{--version} of the tested
programs (see section <A HREF="autoconf.html#SEC166">Writing <TT>`testsuite.at'</TT></A>, <CODE>AT_TESTED</CODE>).
<DT>configuration log
<DD>
The contents of <TT>`config.log'</TT>, as created by @command{configure},
are appended. It contains the configuration flags and a detailed report
on the configuration itself.
</DL>
<H2><A NAME="SEC166" HREF="autoconf_toc.html#TOC166">Writing <TT>`testsuite.at'</TT></A></H2>
<P>
The <TT>`testsuite.at'</TT> is a Bourne shell script making use of special
Autotest M4 macros. It often contains a call to <CODE>AT_INIT</CODE> nears
its beginning followed by one call to <CODE>m4_include</CODE> per source file
for tests. Each such included file, or the remainder of
<TT>`testsuite.at'</TT> if include files are not used, contain a sequence of
test groups. Each test group begins with one call to <CODE>AT_SETUP</CODE>,
it contains an arbitrary number of shell commands or calls to
<CODE>AT_CHECK</CODE>, and it completes with one call to <CODE>AT_CLEANUP</CODE>.
<P>
<DL>
<DT><U>Macro:</U> <B>AT_INIT</B> <I>(@ovar{name})</I>
<DD><A NAME="IDX1018"></A>
<A NAME="IDX1019"></A>
Initialize Autotest. Giving a <VAR>name</VAR> to the test suite is
encouraged if your package includes several test suites. In any case,
the test suite always displays the package name and version. It also
inherits the package bug report address.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AT_TESTED</B> <I>(<VAR>executables</VAR>)</I>
<DD><A NAME="IDX1020"></A>
<A NAME="IDX1021"></A>
Log the path and answer to @option{--version} of each program in
space-separated list <VAR>executables</VAR>. Several invocations register
new executables, in other words, don't fear registering one program
several times.
</DL>
<P>
Autotest test suites rely on the <CODE>PATH</CODE> to find the tested program.
This saves from generating the absolute paths to the various tools, and
makes it possible to test installed programs. Therefore, knowing what
programs are being exercised is crucial to understand some problems in
the test suite itself, or its occasional misuses. It is a good idea to
also subscribe foreign programs you depend upon, to ease incompatibility
diagnostics.
<P>
<DL>
<DT><U>Macro:</U> <B>AT_SETUP</B> <I>(<VAR>test-group-name</VAR>)</I>
<DD><A NAME="IDX1022"></A>
<A NAME="IDX1023"></A>
This macro starts a group of related tests, all to be executed in the
same subshell. It accepts a single argument, which holds a few words
(no more than about 30 or 40 characters) quickly describing the purpose
of the test group being started.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AT_KEYWORDS</B> <I>(<VAR>keywords</VAR>)</I>
<DD><A NAME="IDX1024"></A>
<A NAME="IDX1025"></A>
Associate the space-separated list of <VAR>keywords</VAR> to the enclosing
test group. This makes it possible to run "slices" of the test suite.
For instance if some of your test groups exercise some <SAMP>`foo'</SAMP>
feature, then using <SAMP>`AT_KEYWORDS(foo)'</SAMP> lets you run
<SAMP>`./testsuite -k foo'</SAMP> to run exclusively these test groups. The
<VAR>title</VAR> of the test group is automatically recorded to
<CODE>AT_KEYWORDS</CODE>.
<P>
Several invocations within a test group accumulate new keywords. In
other words, don't fear registering several times the same keyword in a
test group.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AT_CLEANUP</B>
<DD><A NAME="IDX1026"></A>
<A NAME="IDX1027"></A>
End the current test group.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AT_DATA</B> <I>(<VAR>file</VAR>, <VAR>contents</VAR>)</I>
<DD><A NAME="IDX1028"></A>
<A NAME="IDX1029"></A>
Initialize an input data <VAR>file</VAR> with given <VAR>contents</VAR>. Of
course, the <VAR>contents</VAR> have to be properly quoted between square
brackets to protect against included commas or spurious <CODE>m4</CODE>
expansion. The contents ought to end with an end of line.
</DL>
<P>
<DL>
<DT><U>Macro:</U> <B>AT_CHECK</B> <I>(<VAR>commands</VAR>, @dvar{status, <SAMP>`0'</SAMP>}, @ovar{stdout}, @ovar{stderr})</I>
<DD><A NAME="IDX1030"></A>
<A NAME="IDX1031"></A>
Execute a test by performing given shell <VAR>commands</VAR>. These commands
should normally exit with <VAR>status</VAR>, while producing expected
<VAR>stdout</VAR> and <VAR>stderr</VAR> contents. If <VAR>commands</VAR> exit with
status 77, then the whole test group is skipped.
<P>
The <VAR>commands</VAR> <EM>must not</EM> redirect the standard output, nor the
standard error.
<P>
If <VAR>status</VAR>, or <VAR>stdout</VAR>, or <VAR>stderr</VAR> is <SAMP>`ignore'</SAMP>, then
the corresponding value is not checked.
<P>
The special value <SAMP>`expout'</SAMP> for <VAR>stdout</VAR> means the expected
output of the <VAR>commands</VAR> is the content of the file <TT>`expout'</TT>.
If <VAR>stdout</VAR> is <SAMP>`stdout'</SAMP>, then the standard output of the
<VAR>commands</VAR> is available for further tests in the file <TT>`stdout'</TT>.
Similarly for <VAR>stderr</VAR> with <SAMP>`expout'</SAMP> and <SAMP>`stderr'</SAMP>.
</DL>
<H2><A NAME="SEC167" HREF="autoconf_toc.html#TOC167">Running @command{testsuite} Scripts</A></H2>
<P>
<A NAME="IDX1032"></A>
<P>
Autotest test suites support the following arguments:
<DL COMPACT>
<DT><SAMP>`--help'</SAMP>
<DD>
<DT><SAMP>`-h'</SAMP>
<DD>
Display the list of options and exit successfully.
<DT><SAMP>`--version'</SAMP>
<DD>
<DT><SAMP>`-V'</SAMP>
<DD>
Display the version of the test suite and exit successfully.
<DT><SAMP>`--clean'</SAMP>
<DD>
<DT><SAMP>`-c'</SAMP>
<DD>
Remove all the files the test suite might have created and exit. Meant
for <CODE>clean</CODE> Makefile targets.
<DT><SAMP>`--list'</SAMP>
<DD>
<DT><SAMP>`-l'</SAMP>
<DD>
List all the tests (or only the selection), including their possible
keywords.
</DL>
<P>
By default all the tests are performed (or described with
@option{--list}) in the default environment first silently, then
verbosely, but the environment, set of tests, and verbosity level can be
tuned:
<DL COMPACT>
<DT><SAMP>`<VAR>variable</VAR>=<VAR>value</VAR>'</SAMP>
<DD>
Set the environment <VAR>variable</VAR> to <VAR>value</VAR>. Do not run
<SAMP>`FOO=foo ./testsuite'</SAMP> as debugging scripts would then run in a
different environment.
<A NAME="IDX1033"></A>
The variable <CODE>AUTOTEST_PATH</CODE> specifies the testing path to prepend
to <CODE>PATH</CODE>. It handles specially relative paths (not starting with
<SAMP>`/'</SAMP>): they are considered to be relative to the top level of the
package being built. All the directories are made absolute, first
starting from the top level <EM>build</EM> tree, then from the
<EM>source</EM> tree. For instance <SAMP>`./testsuite
AUTOTEST_PATH=tests:bin'</SAMP> for a <TT>`/src/foo-1.0'</TT> source package built
in <TT>`/tmp/foo'</TT> results in <SAMP>`/tmp/foo/tests:/tmp/foo/bin'</SAMP> and
then <SAMP>`/src/foo-1.0/tests:/src/foo-1.0/bin'</SAMP> being prepended to
<CODE>PATH</CODE>.
<DT><SAMP>`<VAR>number</VAR>'</SAMP>
<DD>
<DT><SAMP>`<VAR>number</VAR>-<VAR>number</VAR>'</SAMP>
<DD>
<DT><SAMP>`<VAR>number</VAR>-'</SAMP>
<DD>
<DT><SAMP>`-<VAR>number</VAR>'</SAMP>
<DD>
Add the corresponding test groups, with obvious semantics, to the
selection.
<DT><SAMP>`--keywords=<VAR>keywords</VAR>'</SAMP>
<DD>
<DT><SAMP>`-k <VAR>keywords</VAR>'</SAMP>
<DD>
Add to the selection the test groups which title or keywords (arguments
to <CODE>AT_SETUP</CODE> or <CODE>AT_KEYWORDS</CODE>) match <EM>all</EM> the keywords
of the comma separated list <VAR>keywords</VAR>.
Running <SAMP>`./testsuite -k autoupdate,FUNC'</SAMP> will select all the tests
tagged with <SAMP>`autoupdate'</SAMP> <EM>and</EM> <SAMP>`FUNC'</SAMP> (as in
<SAMP>`AC_CHECK_FUNC'</SAMP>, <SAMP>`AC_FUNC_FNMATCH'</SAMP> etc.) while
<SAMP>`./testsuite -k autoupdate -k FUNC'</SAMP> runs all the tests tagged with
<SAMP>`autoupdate'</SAMP> <EM>or</EM> <SAMP>`FUNC'</SAMP>.
<DT><SAMP>`--errexit'</SAMP>
<DD>
<DT><SAMP>`-e'</SAMP>
<DD>
If any test fails, immediately abort testing. It implies
@option{--debug}: post test group clean up, debugging script generation,
and logging are inhibited. This option is meant for the full test
suite, it is not really useful for generated debugging scripts.
<DT><SAMP>`--verbose'</SAMP>
<DD>
<DT><SAMP>`-v'</SAMP>
<DD>
Force more verbosity in the detailed output of what is being done. This
is the default for debugging scripts.
<DT><SAMP>`--debug'</SAMP>
<DD>
<DT><SAMP>`-d'</SAMP>
<DD>
Do not remove the files after a test group was performed --but they are
still removed <EM>before</EM>, therefore using this option is sane when
running several test groups. Do not create debugging scripts. Do not
log (in order to preserve supposedly existing full log file). This is
the default for debugging scripts.
<DT><SAMP>`--trace'</SAMP>
<DD>
<DT><SAMP>`-x'</SAMP>
<DD>
Trigger shell tracing of the test groups.
</DL>
<H2><A NAME="SEC168" HREF="autoconf_toc.html#TOC168">Making @command{testsuite} Scripts</A></H2>
<P>
For putting Autotest into movement, you need some configuration and
Makefile machinery. We recommend, at least if your package uses deep or
shallow hierarchies, that you use <TT>`tests/'</TT> as the name of the
directory holding all your tests and their <TT>`Makefile'</TT>. Here is a
check list of things to do.
<UL>
<LI>
<A NAME="IDX1034"></A>
Make sure to create the file <TT>`package.m4'</TT>, which defines the
identity of the package. It must define <CODE>AT_PACKAGE_STRING</CODE>, the
full signature of the package, and <CODE>AT_PACKAGE_BUGREPORT</CODE>, the
address to which bug reports should be sent. For sake of completeness,
we suggest that you also define <CODE>AT_PACKAGE_NAME</CODE>,
<CODE>AT_PACKAGE_TARNAME</CODE>, and <CODE>AT_PACKAGE_VERSION</CODE>.
See section <A HREF="autoconf.html#SEC16">Initializing @command{configure}</A>, for a description of these variables. We
suggest the following Makefile excerpt:
<PRE>
$(srcdir)/package.m4: $(top_srcdir)/configure.ac
{ \
echo '# Signature of the current package.'; \
echo 'm4_define([AT_PACKAGE_NAME], [@PACKAGE_NAME@])'; \
echo 'm4_define([AT_PACKAGE_TARNAME], [@PACKAGE_TARNAME@])'; \
echo 'm4_define([AT_PACKAGE_VERSION], [@PACKAGE_VERSION@])'; \
echo 'm4_define([AT_PACKAGE_STRING], [@PACKAGE_STRING@])'; \
echo 'm4_define([AT_PACKAGE_BUGREPORT], [@PACKAGE_BUGREPORT@])'; \
} >$(srcdir)/package.m4
</PRE>
Be sure to distribute <TT>`package.m4'</TT> and to put it into the source
hierarchy: the test suite ought to be shipped!
<LI>
Use the <CODE>AT_CONFIG</CODE> macro from within file <TT>`configure.ac'</TT>.
This macro accepts one argument, which is the directory, relative to the
test directory, where the executables are prepared.
<LI>
Still within <TT>`configure.ac'</TT>, ensure that some
<CODE>AC_CONFIG_FILES</CODE> command includes substitution for
<TT>`tests/atconfig'</TT> and also, as appropriate, <TT>`tests/atlocal'</TT>.
<LI>
The <TT>`tests/Makefile.in'</TT> should be modified so the validation in
your package is triggered by <SAMP>`make check'</SAMP>. An example is provided
below.
</UL>
<P>
With Automake, here is a minimal example about how to link <SAMP>`make
check'</SAMP> with a validation suite.
<PRE>
EXTRA_DIST = testsuite.at testsuite
TESTSUITE = $(srcdir)/testsuite
check-local: atconfig atlocal $(TESTSUITE)
$(SHELL) $(TESTSUITE)
AUTOTEST = $(AUTOM4TE) --language=autotest
$(TESTSUITE): $(srcdir)/testsuite.at
$(AUTOTEST) -I $(srcdir) $.at -o $.tmp
mv $.tmp $
</PRE>
<P>
You might want to list explicitly the dependencies, i.e., the list of
the files <TT>`testsuite.at'</TT> includes.
<P>
With strict Autoconf, you might need to add lines inspired from the
following:
<PRE>
subdir = tests
atconfig: $(top_builddir)/config.status
cd $(top_builddir) && \
$(SHELL) ./config.status $(subdir)/$
atlocal: $(srcdir)/atlocal.in $(top_builddir)/config.status
cd $(top_builddir) && \
$(SHELL) ./config.status $(subdir)/$
</PRE>
<P>
and manage to have <TT>`atconfig.in'</TT> and <CODE>$(EXTRA_DIST)</CODE>
distributed.
<H1><A NAME="SEC169" HREF="autoconf_toc.html#TOC169">Questions About Autoconf</A></H1>
<P>
Several questions about Autoconf come up occasionally. Here some of them
are addressed.
<H2><A NAME="SEC170" HREF="autoconf_toc.html#TOC170">Distributing @command{configure} Scripts</A></H2>
<PRE>
What are the restrictions on distributing @command{configure}
scripts that Autoconf generates? How does that affect my
programs that use them?
</PRE>
<P>
There are no restrictions on how the configuration scripts that Autoconf
produces may be distributed or used. In Autoconf version 1, they were
covered by the GNU General Public License. We still encourage
software authors to distribute their work under terms like those of the
GPL, but doing so is not required to use Autoconf.
<P>
Of the other files that might be used with @command{configure},
<TT>`config.h.in'</TT> is under whatever copyright you use for your
<TT>`configure.ac'</TT>. <TT>`config.sub'</TT> and <TT>`config.guess'</TT> have an
exception to the GPL when they are used with an Autoconf-generated
@command{configure} script, which permits you to distribute them under the
same terms as the rest of your package. <TT>`install-sh'</TT> is from the X
Consortium and is not copyrighted.
<H2><A NAME="SEC171" HREF="autoconf_toc.html#TOC171">Why Require GNU M4?</A></H2>
<PRE>
Why does Autoconf require GNU M4?
</PRE>
<P>
Many M4 implementations have hard-coded limitations on the size and
number of macros that Autoconf exceeds. They also lack several
builtin macros that it would be difficult to get along without in a
sophisticated application like Autoconf, including:
<PRE>
m4_builtin
m4_indir
m4_bpatsubst
__file__
__line__
</PRE>
<P>
Autoconf requires version 1.4 or above of GNU M4 because it uses
frozen state files.
<P>
Since only software maintainers need to use Autoconf, and since GNU
M4 is simple to configure and install, it seems reasonable to require
GNU M4 to be installed also. Many maintainers of GNU and
other free software already have most of the GNU utilities
installed, since they prefer them.
<H2><A NAME="SEC172" HREF="autoconf_toc.html#TOC172">How Can I Bootstrap?</A></H2>
<PRE>
If Autoconf requires GNU M4 and GNU M4 has an Autoconf
@command{configure} script, how do I bootstrap? It seems like a chicken
and egg problem!
</PRE>
<P>
This is a misunderstanding. Although GNU M4 does come with a
@command{configure} script produced by Autoconf, Autoconf is not required
in order to run the script and install GNU M4. Autoconf is only
required if you want to change the M4 @command{configure} script, which few
people have to do (mainly its maintainer).
<H2><A NAME="SEC173" HREF="autoconf_toc.html#TOC173">Why Not Imake?</A></H2>
<PRE>
Why not use Imake instead of @command{configure} scripts?
</PRE>
<P>
Several people have written addressing this question, so I include
adaptations of their explanations here.
<P>
The following answer is based on one written by Richard Pixley:
<BLOCKQUOTE>
<P>
Autoconf generated scripts frequently work on machines that it has
never been set up to handle before. That is, it does a good job of
inferring a configuration for a new system. Imake cannot do this.
<P>
Imake uses a common database of host specific data. For X11, this makes
sense because the distribution is made as a collection of tools, by one
central authority who has control over the database.
<P>
GNU tools are not released this way. Each GNU tool has a
maintainer; these maintainers are scattered across the world. Using a
common database would be a maintenance nightmare. Autoconf may appear
to be this kind of database, but in fact it is not. Instead of listing
host dependencies, it lists program requirements.
<P>
If you view the GNU suite as a collection of native tools, then the
problems are similar. But the GNU development tools can be
configured as cross tools in almost any host+target permutation. All of
these configurations can be installed concurrently. They can even be
configured to share host independent files across hosts. Imake doesn't
address these issues.
<P>
Imake templates are a form of standardization. The GNU coding
standards address the same issues without necessarily imposing the same
restrictions.
</BLOCKQUOTE>
<P>
Here is some further explanation, written by Per Bothner:
<BLOCKQUOTE>
<P>
One of the advantages of Imake is that it easy to generate large
Makefiles using <CODE>cpp</CODE>'s <SAMP>`#include'</SAMP> and macro mechanisms.
However, <CODE>cpp</CODE> is not programmable: it has limited conditional
facilities, and no looping. And <CODE>cpp</CODE> cannot inspect its
environment.
<P>
All of these problems are solved by using <CODE>sh</CODE> instead of
<CODE>cpp</CODE>. The shell is fully programmable, has macro substitution,
can execute (or source) other shell scripts, and can inspect its
environment.
</BLOCKQUOTE>
<P>
Paul Eggert elaborates more:
<BLOCKQUOTE>
<P>
With Autoconf, installers need not assume that Imake itself is already
installed and working well. This may not seem like much of an advantage
to people who are accustomed to Imake. But on many hosts Imake is not
installed or the default installation is not working well, and requiring
Imake to install a package hinders the acceptance of that package on
those hosts. For example, the Imake template and configuration files
might not be installed properly on a host, or the Imake build procedure
might wrongly assume that all source files are in one big directory
tree, or the Imake configuration might assume one compiler whereas the
package or the installer needs to use another, or there might be a
version mismatch between the Imake expected by the package and the Imake
supported by the host. These problems are much rarer with Autoconf,
where each package comes with its own independent configuration
processor.
<P>
Also, Imake often suffers from unexpected interactions between
<CODE>make</CODE> and the installer's C preprocessor. The fundamental problem
here is that the C preprocessor was designed to preprocess C programs,
not <TT>`Makefile'</TT>s. This is much less of a problem with Autoconf,
which uses the general-purpose preprocessor <CODE>m4</CODE>, and where the
package's author (rather than the installer) does the preprocessing in a
standard way.
</BLOCKQUOTE>
<P>
Finally, Mark Eichin notes:
<BLOCKQUOTE>
<P>
Imake isn't all that extensible, either. In order to add new features to
Imake, you need to provide your own project template, and duplicate most
of the features of the existing one. This means that for a sophisticated
project, using the vendor-provided Imake templates fails to provide any
leverage--since they don't cover anything that your own project needs
(unless it is an X11 program).
<P>
On the other side, though:
<P>
The one advantage that Imake has over @command{configure}:
<TT>`Imakefile'</TT>s tend to be much shorter (likewise, less redundant)
than <TT>`Makefile.in'</TT>s. There is a fix to this, however--at least
for the Kerberos V5 tree, we've modified things to call in common
<TT>`post.in'</TT> and <TT>`pre.in'</TT> <TT>`Makefile'</TT> fragments for the
entire tree. This means that a lot of common things don't have to be
duplicated, even though they normally are in @command{configure} setups.
</BLOCKQUOTE>
<H1><A NAME="SEC174" HREF="autoconf_toc.html#TOC174">History of Autoconf</A></H1>
<P>
You may be wondering, Why was Autoconf originally written? How did it
get into its present form? (Why does it look like gorilla spit?) If
you're not wondering, then this chapter contains no information useful
to you, and you might as well skip it. If you <EM>are</EM> wondering,
then let there be light...
<H2><A NAME="SEC175" HREF="autoconf_toc.html#TOC175">Genesis</A></H2>
<P>
In June 1991 I was maintaining many of the GNU utilities for the
Free Software Foundation. As they were ported to more platforms and
more programs were added, the number of @option{-D} options that users
had to select in the <TT>`Makefile'</TT> (around 20) became burdensome.
Especially for me--I had to test each new release on a bunch of
different systems. So I wrote a little shell script to guess some of
the correct settings for the fileutils package, and released it as part
of fileutils 2.0. That @command{configure} script worked well enough that
the next month I adapted it (by hand) to create similar @command{configure}
scripts for several other GNU utilities packages. Brian Berliner
also adapted one of my scripts for his CVS revision control system.
<P>
Later that summer, I learned that Richard Stallman and Richard Pixley
were developing similar scripts to use in the GNU compiler tools;
so I adapted my @command{configure} scripts to support their evolving
interface: using the file name <TT>`Makefile.in'</TT> as the templates;
adding <SAMP>`+srcdir'</SAMP>, the first option (of many); and creating
<TT>`config.status'</TT> files.
<H2><A NAME="SEC176" HREF="autoconf_toc.html#TOC176">Exodus</A></H2>
<P>
As I got feedback from users, I incorporated many improvements, using
Emacs to search and replace, cut and paste, similar changes in each of
the scripts. As I adapted more GNU utilities packages to use
@command{configure} scripts, updating them all by hand became impractical.
Rich Murphey, the maintainer of the GNU graphics utilities, sent me
mail saying that the @command{configure} scripts were great, and asking if
I had a tool for generating them that I could send him. No, I thought,
but I should! So I started to work out how to generate them. And the
journey from the slavery of hand-written @command{configure} scripts to the
abundance and ease of Autoconf began.
<P>
Cygnus @command{configure}, which was being developed at around that time,
is table driven; it is meant to deal mainly with a discrete number of
system types with a small number of mainly unguessable features (such as
details of the object file format). The automatic configuration system
that Brian Fox had developed for Bash takes a similar approach. For
general use, it seems to me a hopeless cause to try to maintain an
up-to-date database of which features each variant of each operating
system has. It's easier and more reliable to check for most features on
the fly--especially on hybrid systems that people have hacked on
locally or that have patches from vendors installed.
<P>
I considered using an architecture similar to that of Cygnus
@command{configure}, where there is a single @command{configure} script that
reads pieces of <TT>`configure.in'</TT> when run. But I didn't want to have
to distribute all of the feature tests with every package, so I settled
on having a different @command{configure} made from each
<TT>`configure.in'</TT> by a preprocessor. That approach also offered more
control and flexibility.
<P>
I looked briefly into using the Metaconfig package, by Larry Wall,
Harlan Stenn, and Raphael Manfredi, but I decided not to for several
reasons. The @command{Configure} scripts it produces are interactive,
which I find quite inconvenient; I didn't like the ways it checked for
some features (such as library functions); I didn't know that it was
still being maintained, and the @command{Configure} scripts I had
seen didn't work on many modern systems (such as System V R4 and NeXT);
it wasn't very flexible in what it could do in response to a feature's
presence or absence; I found it confusing to learn; and it was too big
and complex for my needs (I didn't realize then how much Autoconf would
eventually have to grow).
<P>
I considered using Perl to generate my style of @command{configure}
scripts, but decided that M4 was better suited to the job of simple
textual substitutions: it gets in the way less, because output is
implicit. Plus, everyone already has it. (Initially I didn't rely on
the GNU extensions to M4.) Also, some of my friends at the
University of Maryland had recently been putting M4 front ends on
several programs, including <CODE>tvtwm</CODE>, and I was interested in trying
out a new language.
<H2><A NAME="SEC177" HREF="autoconf_toc.html#TOC177">Leviticus</A></H2>
<P>
Since my @command{configure} scripts determine the system's capabilities
automatically, with no interactive user intervention, I decided to call
the program that generates them Autoconfig. But with a version number
tacked on, that name would be too long for old UNIX file systems,
so I shortened it to Autoconf.
<P>
In the fall of 1991 I called together a group of fellow questers after
the Holy Grail of portability (er, that is, alpha testers) to give me
feedback as I encapsulated pieces of my handwritten scripts in M4 macros
and continued to add features and improve the techniques used in the
checks. Prominent among the testers were Fran@,cois Pinard, who came up
with the idea of making an <TT>`autoconf'</TT> shell script to run <CODE>m4</CODE>
and check for unresolved macro calls; Richard Pixley, who suggested
running the compiler instead of searching the file system to find
include files and symbols, for more accurate results; Karl Berry, who
got Autoconf to configure TeX and added the macro index to the
documentation; and Ian Lance Taylor, who added support for creating a C
header file as an alternative to putting @option{-D} options in a
<TT>`Makefile'</TT>, so he could use Autoconf for his UUCP package.
The alpha testers cheerfully adjusted their files again and again as the
names and calling conventions of the Autoconf macros changed from
release to release. They all contributed many specific checks, great
ideas, and bug fixes.
<H2><A NAME="SEC178" HREF="autoconf_toc.html#TOC178">Numbers</A></H2>
<P>
In July 1992, after months of alpha testing, I released Autoconf 1.0,
and converted many GNU packages to use it. I was surprised by how
positive the reaction to it was. More people started using it than I
could keep track of, including people working on software that wasn't
part of the GNU Project (such as TCL, FSP, and Kerberos V5).
Autoconf continued to improve rapidly, as many people using the
@command{configure} scripts reported problems they encountered.
<P>
Autoconf turned out to be a good torture test for M4 implementations.
UNIX <CODE>m4</CODE> started to dump core because of the length of the
macros that Autoconf defined, and several bugs showed up in GNU
<CODE>m4</CODE> as well. Eventually, we realized that we needed to use some
features that only GNU M4 has. 4.3BSD <CODE>m4</CODE>, in
particular, has an impoverished set of builtin macros; the System V
version is better, but still doesn't provide everything we need.
<P>
More development occurred as people put Autoconf under more stresses
(and to uses I hadn't anticipated). Karl Berry added checks for X11.
david zuhn contributed C++ support. Fran@,cois Pinard made it diagnose
invalid arguments. Jim Blandy bravely coerced it into configuring
GNU Emacs, laying the groundwork for several later improvements.
Roland McGrath got it to configure the GNU C Library, wrote the
@command{autoheader} script to automate the creation of C header file
templates, and added a @option{--verbose} option to @command{configure}.
Noah Friedman added the @option{--autoconf-dir} option and
<CODE>AC_MACRODIR</CODE> environment variable. (He also coined the term
<EM>autoconfiscate</EM> to mean "adapt a software package to use
Autoconf".) Roland and Noah improved the quoting protection in
<CODE>AC_DEFINE</CODE> and fixed many bugs, especially when I got sick of
dealing with portability problems from February through June, 1993.
<H2><A NAME="SEC179" HREF="autoconf_toc.html#TOC179">Deuteronomy</A></H2>
<P>
A long wish list for major features had accumulated, and the effect of
several years of patching by various people had left some residual
cruft. In April 1994, while working for Cygnus Support, I began a major
revision of Autoconf. I added most of the features of the Cygnus
@command{configure} that Autoconf had lacked, largely by adapting the
relevant parts of Cygnus @command{configure} with the help of david zuhn
and Ken Raeburn. These features include support for using
<TT>`config.sub'</TT>, <TT>`config.guess'</TT>, @option{--host}, and
@option{--target}; making links to files; and running @command{configure}
scripts in subdirectories. Adding these features enabled Ken to convert
GNU <CODE>as</CODE>, and Rob Savoye to convert DejaGNU, to using
Autoconf.
<P>
I added more features in response to other peoples' requests. Many
people had asked for @command{configure} scripts to share the results of
the checks between runs, because (particularly when configuring a large
source tree, like Cygnus does) they were frustratingly slow. Mike
Haertel suggested adding site-specific initialization scripts. People
distributing software that had to unpack on MS-DOS asked for a way to
override the <TT>`.in'</TT> extension on the file names, which produced file
names like <TT>`config.h.in'</TT> containing two dots. Jim Avera did an
extensive examination of the problems with quoting in <CODE>AC_DEFINE</CODE>
and <CODE>AC_SUBST</CODE>; his insights led to significant improvements.
Richard Stallman asked that compiler output be sent to <TT>`config.log'</TT>
instead of <TT>`/dev/null'</TT>, to help people debug the Emacs
@command{configure} script.
<P>
I made some other changes because of my dissatisfaction with the quality
of the program. I made the messages showing results of the checks less
ambiguous, always printing a result. I regularized the names of the
macros and cleaned up coding style inconsistencies. I added some
auxiliary utilities that I had developed to help convert source code
packages to use Autoconf. With the help of Fran@,cois Pinard, I made
the macros not interrupt each others' messages. (That feature revealed
some performance bottlenecks in GNU <CODE>m4</CODE>, which he hastily
corrected!) I reorganized the documentation around problems people want
to solve. And I began a test suite, because experience had shown that
Autoconf has a pronounced tendency to regress when we change it.
<P>
Again, several alpha testers gave invaluable feedback, especially
Fran@,cois Pinard, Jim Meyering, Karl Berry, Rob Savoye, Ken Raeburn,
and Mark Eichin.
<P>
Finally, version 2.0 was ready. And there was much rejoicing. (And I
have free time again. I think. Yeah, right.)
<H1><A NAME="SEC180" HREF="autoconf_toc.html#TOC180">Copying This Manual</A></H1>
<H2><A NAME="SEC181" HREF="autoconf_toc.html#TOC181">GNU Free Documentation License</A></H2>
<P>
<A NAME="IDX1035"></A>
Version 1.1, March 2000
<PRE>
Copyright (C) 2000 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
</PRE>
<OL>
<LI>
PREAMBLE
The purpose of this License is to make a manual, textbook, or other
written document <EM>free</EM> in the sense of freedom: to assure everyone
the effective freedom to copy and redistribute it, with or without
modifying it, either commercially or noncommercially. Secondarily,
this License preserves for the author and publisher a way to get
credit for their work, while not being considered responsible for
modifications made by others.
This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense. It
complements the GNU General Public License, which is a copyleft
license designed for free software.
We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does. But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book. We recommend this License
principally for works whose purpose is instruction or reference.
<LI>
APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work that contains a
notice placed by the copyright holder saying it can be distributed
under the terms of this License. The "Document", below, refers to any
such manual or work. Any member of the public is a licensee, and is
addressed as "you".
A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.
A "Secondary Section" is a named appendix or a front-matter section of
the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall subject
(or to related matters) and contains nothing that could fall directly
within that overall subject. (For example, if the Document is in part a
textbook of mathematics, a Secondary Section may not explain any
mathematics.) The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.
The "Invariant Sections" are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License.
The "Cover Texts" are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License.
A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, whose contents can be viewed and edited directly and
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters. A copy made in an otherwise Transparent file
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not "Transparent" is called "Opaque".
Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format,
@acronym{SGML} or @acronym{XML} using a publicly available
@acronym{DTD}, and standard-conforming simple @acronym{HTML} designed
for human modification. Opaque formats include PostScript,
@acronym{PDF}, proprietary formats that can be read and edited only by
proprietary word processors, @acronym{SGML} or @acronym{XML} for which
the @acronym{DTD} and/or processing tools are not generally available,
and the machine-generated @acronym{HTML} produced by some word
processors for output purposes only.
The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page. For works in
formats which do not have any title page as such, "Title Page" means
the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text.
<LI>
VERBATIM COPYING
You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License. You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute. However, you may accept
compensation in exchange for copies. If you distribute a large enough
number of copies you must also follow the conditions in section 3.
You may also lend copies, under the same conditions stated above, and
you may publicly display copies.
<LI>
COPYING IN QUANTITY
If you publish printed copies of the Document numbering more than 100,
and the Document's license notice requires Cover Texts, you must enclose
the copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover. Both covers must also clearly and legibly identify
you as the publisher of these copies. The front cover must present
the full title with all words of the title equally prominent and
visible. You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.
If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.
If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a publicly-accessible computer-network location containing a complete
Transparent copy of the Document, free of added material, which the
general network-using public has access to download anonymously at no
charge using public-standard network protocols. If you use the latter
option, you must take reasonably prudent steps, when you begin
distribution of Opaque copies in quantity, to ensure that this
Transparent copy will remain thus accessible at the stated location
until at least one year after the last time you distribute an Opaque
copy (directly or through your agents or retailers) of that edition to
the public.
It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.
<LI>
MODIFICATIONS
You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it. In addition, you must do these things in the Modified Version:
<OL>
<LI>
Use in the Title Page (and on the covers, if any) a title distinct
from that of the Document, and from those of previous versions
(which should, if there were any, be listed in the History section
of the Document). You may use the same title as a previous version
if the original publisher of that version gives permission.
<LI>
List on the Title Page, as authors, one or more persons or entities
responsible for authorship of the modifications in the Modified
Version, together with at least five of the principal authors of the
Document (all of its principal authors, if it has less than five).
<LI>
State on the Title page the name of the publisher of the
Modified Version, as the publisher.
<LI>
Preserve all the copyright notices of the Document.
<LI>
Add an appropriate copyright notice for your modifications
adjacent to the other copyright notices.
<LI>
Include, immediately after the copyright notices, a license notice
giving the public permission to use the Modified Version under the
terms of this License, in the form shown in the Addendum below.
<LI>
Preserve in that license notice the full lists of Invariant Sections
and required Cover Texts given in the Document's license notice.
<LI>
Include an unaltered copy of this License.
<LI>
Preserve the section entitled "History", and its title, and add to
it an item stating at least the title, year, new authors, and
publisher of the Modified Version as given on the Title Page. If
there is no section entitled "History" in the Document, create one
stating the title, year, authors, and publisher of the Document as
given on its Title Page, then add an item describing the Modified
Version as stated in the previous sentence.
<LI>
Preserve the network location, if any, given in the Document for
public access to a Transparent copy of the Document, and likewise
the network locations given in the Document for previous versions
it was based on. These may be placed in the "History" section.
You may omit a network location for a work that was published at
least four years before the Document itself, or if the original
publisher of the version it refers to gives permission.
<LI>
In any section entitled "Acknowledgments" or "Dedications",
preserve the section's title, and preserve in the section all the
substance and tone of each of the contributor acknowledgments
and/or dedications given therein.
<LI>
Preserve all the Invariant Sections of the Document,
unaltered in their text and in their titles. Section numbers
or the equivalent are not considered part of the section titles.
<LI>
Delete any section entitled "Endorsements". Such a section
may not be included in the Modified Version.
<LI>
Do not retitle any existing section as "Endorsements"
or to conflict in title with any Invariant Section.
</OL>
If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant. To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.
You may add a section entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.
You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version. Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity. If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.
The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.
<LI>
COMBINING DOCUMENTS
You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice.
The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy. If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.
In the combination, you must combine any sections entitled "History"
in the various original documents, forming one section entitled
"History"; likewise combine any sections entitled "Acknowledgments",
and any sections entitled "Dedications". You must delete all sections
entitled "Endorsements."
<LI>
COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.
You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.
<LI>
AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, does not as a whole count as a Modified Version
of the Document, provided no compilation copyright is claimed for the
compilation. Such a compilation is called an "aggregate", and this
License does not apply to the other self-contained works thus compiled
with the Document, on account of their being thus compiled, if they
are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one quarter
of the entire aggregate, the Document's Cover Texts may be placed on
covers that surround only the Document within the aggregate.
Otherwise they must appear on covers around the whole aggregate.
<LI>
TRANSLATION
Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections. You may include a
translation of this License provided that you also include the
original English version of this License. In case of a disagreement
between the translation and the original English version of this
License, the original English version will prevail.
<LI>
TERMINATION
You may not copy, modify, sublicense, or distribute the Document except
as expressly provided for under this License. Any other attempt to
copy, modify, sublicense or distribute the Document is void, and will
automatically terminate your rights under this License. However,
parties who have received copies, or rights, from you under this
License will not have their licenses terminated so long as such
parties remain in full compliance.
<LI>
FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time. Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns. See
<A HREF="http://www.gnu.org/copyleft/">http://www.gnu.org/copyleft/</A>.
Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License "or any later version" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation. If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.
</OL>
<H3><A NAME="SEC182" HREF="autoconf_toc.html#TOC182">ADDENDUM: How to use this License for your documents</A></H3>
<P>
To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:
<PRE>
Copyright (C) <VAR>year</VAR> <VAR>your name</VAR>.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation;
with the Invariant Sections being <VAR>list their titles</VAR>, with the
Front-Cover Texts being <VAR>list</VAR>, and with the Back-Cover Texts being <VAR>list</VAR>.
A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
</PRE>
<P>
If you have no Invariant Sections, write "with no Invariant Sections"
instead of saying which ones are invariant. If you have no
Front-Cover Texts, write "no Front-Cover Texts" instead of
"Front-Cover Texts being <VAR>list</VAR>"; likewise for Back-Cover Texts.
<P>
If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.
<H1><A NAME="SEC183" HREF="autoconf_toc.html#TOC183">Indices</A></H1>
<H2><A NAME="SEC184" HREF="autoconf_toc.html#TOC184">Environment Variable Index</A></H2>
<P>
This is an alphabetical list of the environment variables that Autoconf
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Jump to:
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<DIR>
<LI><A HREF="autoconf.html#IDX698">CDPATH</A>
<LI><A HREF="autoconf.html#IDX796">CONFIG_COMMANDS</A>
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<LI><A HREF="autoconf.html#IDX802">CONFIG_LINKS</A>
<LI><A HREF="autoconf.html#IDX792">CONFIG_SHELL</A>
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<H2><A NAME="evindex_n">n</A></H2>
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<LI><A HREF="autoconf.html#IDX709">NULLCMD</A>
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<H2><A NAME="evindex_p">p</A></H2>
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<H2><A NAME="evindex_r">r</A></H2>
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<LI><A HREF="autoconf.html#IDX712">RANDOM</A>
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<H2><A NAME="SEC185" HREF="autoconf_toc.html#TOC185">Output Variable Index</A></H2>
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This is an alphabetical list of the variables that Autoconf can
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<LI><A HREF="autoconf.html#IDX220">ALLOCA</A>
<LI><A HREF="autoconf.html#IDX160">AWK</A>
</DIR>
<H2><A NAME="ovindex_b">b</A></H2>
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<LI><A HREF="autoconf.html#IDX92">bindir</A>
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<H2><A NAME="ovindex_c">c</A></H2>
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<LI><A HREF="autoconf.html#IDX56">configure_input</A>
<LI><A HREF="autoconf.html#IDX475">CPP</A>
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<H2><A NAME="ovindex_d">d</A></H2>
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<H2><A NAME="ovindex_e">e</A></H2>
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<LI><A HREF="autoconf.html#IDX66">ECHO_C</A>
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<LI><A HREF="autoconf.html#IDX96">exec_prefix</A>
<LI><A HREF="autoconf.html#IDX459">EXEEXT</A>, <A HREF="autoconf.html#IDX842">EXEEXT</A>
</DIR>
<H2><A NAME="ovindex_f">f</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX515">F77</A>
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<H2><A NAME="ovindex_g">g</A></H2>
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<H2><A NAME="ovindex_h">h</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX764">host</A>
<LI><A HREF="autoconf.html#IDX754">host_alias</A>
<LI><A HREF="autoconf.html#IDX765">host_cpu</A>
<LI><A HREF="autoconf.html#IDX767">host_os</A>
<LI><A HREF="autoconf.html#IDX766">host_vendor</A>
</DIR>
<H2><A NAME="ovindex_i">i</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX98">includedir</A>
<LI><A HREF="autoconf.html#IDX100">infodir</A>
<LI><A HREF="autoconf.html#IDX163">INSTALL</A>
<LI><A HREF="autoconf.html#IDX165">INSTALL_DATA</A>
<LI><A HREF="autoconf.html#IDX164">INSTALL_PROGRAM</A>
<LI><A HREF="autoconf.html#IDX166">INSTALL_SCRIPT</A>
</DIR>
<H2><A NAME="ovindex_k">k</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX264">KMEM_GROUP</A>
</DIR>
<H2><A NAME="ovindex_l">l</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX72">LDFLAGS</A>
<LI><A HREF="autoconf.html#IDX169">LEX</A>
<LI><A HREF="autoconf.html#IDX172">LEX_OUTPUT_ROOT</A>
<LI><A HREF="autoconf.html#IDX170">LEXLIB</A>
<LI><A HREF="autoconf.html#IDX102">libdir</A>
<LI><A HREF="autoconf.html#IDX104">libexecdir</A>
<LI><A HREF="autoconf.html#IDX262">LIBOBJS</A>, <A HREF="autoconf.html#IDX285">LIBOBJS</A>, <A HREF="autoconf.html#IDX289">LIBOBJS</A>, <A HREF="autoconf.html#IDX359">LIBOBJS</A>, <A HREF="autoconf.html#IDX366">LIBOBJS</A>, <A HREF="autoconf.html#IDX417">LIBOBJS</A>
<LI><A HREF="autoconf.html#IDX74">LIBS</A>, <A HREF="autoconf.html#IDX563">LIBS</A>, <A HREF="autoconf.html#IDX952">LIBS</A>, <A HREF="autoconf.html#IDX1011">LIBS</A>
<LI><A HREF="autoconf.html#IDX175">LN_S</A>
<LI><A HREF="autoconf.html#IDX106">localstatedir</A>
</DIR>
<H2><A NAME="ovindex_m">m</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX108">mandir</A>
</DIR>
<H2><A NAME="ovindex_n">n</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX263">NEED_SETGID</A>
</DIR>
<H2><A NAME="ovindex_o">o</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX460">OBJEXT</A>, <A HREF="autoconf.html#IDX919">OBJEXT</A>
<LI><A HREF="autoconf.html#IDX110">oldincludedir</A>
</DIR>
<H2><A NAME="ovindex_p">p</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX30">PACKAGE_BUGREPORT</A>
<LI><A HREF="autoconf.html#IDX18">PACKAGE_NAME</A>
<LI><A HREF="autoconf.html#IDX27">PACKAGE_STRING</A>
<LI><A HREF="autoconf.html#IDX21">PACKAGE_TARNAME</A>
<LI><A HREF="autoconf.html#IDX24">PACKAGE_VERSION</A>
<LI><A HREF="autoconf.html#IDX327">POW_LIB</A>
<LI><A HREF="autoconf.html#IDX112">prefix</A>
<LI><A HREF="autoconf.html#IDX786">program_transform_name</A>
</DIR>
<H2><A NAME="ovindex_r">r</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX178">RANLIB</A>
</DIR>
<H2><A NAME="ovindex_s">s</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX114">sbindir</A>
<LI><A HREF="autoconf.html#IDX50">SET_MAKE</A>
<LI><A HREF="autoconf.html#IDX116">sharedstatedir</A>
<LI><A HREF="autoconf.html#IDX84">srcdir</A>
<LI><A HREF="autoconf.html#IDX151">subdirs</A>
<LI><A HREF="autoconf.html#IDX118">sysconfdir</A>
</DIR>
<H2><A NAME="ovindex_t">t</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX770">target</A>
<LI><A HREF="autoconf.html#IDX755">target_alias</A>
<LI><A HREF="autoconf.html#IDX771">target_cpu</A>
<LI><A HREF="autoconf.html#IDX773">target_os</A>
<LI><A HREF="autoconf.html#IDX772">target_vendor</A>
<LI><A HREF="autoconf.html#IDX80">top_builddir</A>
<LI><A HREF="autoconf.html#IDX88">top_srcdir</A>
</DIR>
<H2><A NAME="ovindex_x">x</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX539">X_CFLAGS</A>
<LI><A HREF="autoconf.html#IDX541">X_EXTRA_LIBS</A>
<LI><A HREF="autoconf.html#IDX540">X_LIBS</A>
<LI><A HREF="autoconf.html#IDX542">X_PRE_LIBS</A>
</DIR>
<H2><A NAME="ovindex_y">y</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX181">YACC</A>
</DIR>
<H2><A NAME="SEC186" HREF="autoconf_toc.html#TOC186">Preprocessor Symbol Index</A></H2>
<P>
This is an alphabetical list of the C preprocessor symbols that the
Autoconf macros define. To work with Autoconf, C source code needs to
use these names in <CODE>#if</CODE> directives.
<P>
Jump to:
<A HREF="#cvindex__">_</A>
-
<A HREF="#cvindex_c">c</A>
-
<A HREF="#cvindex_d">d</A>
-
<A HREF="#cvindex_f">f</A>
-
<A HREF="#cvindex_g">g</A>
-
<A HREF="#cvindex_h">h</A>
-
<A HREF="#cvindex_i">i</A>
-
<A HREF="#cvindex_l">l</A>
-
<A HREF="#cvindex_m">m</A>
-
<A HREF="#cvindex_n">n</A>
-
<A HREF="#cvindex_o">o</A>
-
<A HREF="#cvindex_p">p</A>
-
<A HREF="#cvindex_r">r</A>
-
<A HREF="#cvindex_s">s</A>
-
<A HREF="#cvindex_t">t</A>
-
<A HREF="#cvindex_u">u</A>
-
<A HREF="#cvindex_v">v</A>
-
<A HREF="#cvindex_w">w</A>
-
<A HREF="#cvindex_x">x</A>
-
<A HREF="#cvindex_y">y</A>
<P>
<H2><A NAME="cvindex__">_</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX491">__CHAR_UNSIGNED__</A>
<LI><A HREF="autoconf.html#IDX501">__PROTOTYPES</A>
<LI><A HREF="autoconf.html#IDX560">_ALL_SOURCE</A>
<LI><A HREF="autoconf.html#IDX548">_FILE_OFFSET_BITS</A>
<LI><A HREF="autoconf.html#IDX549">_LARGE_FILES</A>
<LI><A HREF="autoconf.html#IDX245">_LARGEFILE_SOURCE</A>
<LI><A HREF="autoconf.html#IDX566">_MINIX</A>
<LI><A HREF="autoconf.html#IDX568">_POSIX_1_SOURCE</A>
<LI><A HREF="autoconf.html#IDX567">_POSIX_SOURCE</A>
<LI><A HREF="autoconf.html#IDX387">_POSIX_VERSION</A>
</DIR>
<H2><A NAME="cvindex_c">c</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX218">C_ALLOCA</A>
<LI><A HREF="autoconf.html#IDX261">C_GETLOADAVG</A>
<LI><A HREF="autoconf.html#IDX227">CLOSEDIR_VOID</A>
<LI><A HREF="autoconf.html#IDX482">const</A>
</DIR>
<H2><A NAME="cvindex_d">d</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX254">DGUX</A>
<LI><A HREF="autoconf.html#IDX834">DIRENT</A>
</DIR>
<H2><A NAME="cvindex_f">f</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX525">F77_DUMMY_MAIN</A>
<LI><A HREF="autoconf.html#IDX531">F77_FUNC</A>
<LI><A HREF="autoconf.html#IDX532">F77_FUNC_</A>
<LI><A HREF="autoconf.html#IDX528">F77_MAIN</A>
<LI><A HREF="autoconf.html#IDX519">F77_NO_MINUS_C_MINUS_O</A>
</DIR>
<H2><A NAME="cvindex_g">g</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX435">GETGROUPS_T</A>
<LI><A HREF="autoconf.html#IDX259">GETLODAVG_PRIVILEGED</A>
<LI><A HREF="autoconf.html#IDX273">GETPGRP_VOID</A>
<LI><A HREF="autoconf.html#IDX454">gid_t</A>
<LI><A HREF="autoconf.html#IDX393">GWINSZ_IN_SYS_IOCTL</A>
</DIR>
<H2><A NAME="cvindex_h">h</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX219">HAVE_ALLOCA_H</A>
<LI><A HREF="autoconf.html#IDX123">HAVE_CONFIG_H</A>
<LI><A HREF="autoconf.html#IDX332">HAVE_DECL_STRERROR_R</A>
<LI><A HREF="autoconf.html#IDX407">HAVE_DECL_<VAR>symbol</VAR></A>
<LI><A HREF="autoconf.html#IDX370">HAVE_DIRENT_H</A>
<LI><A HREF="autoconf.html#IDX350">HAVE_DOPRNT</A>
<LI><A HREF="autoconf.html#IDX356">HAVE_<VAR>function</VAR></A>
<LI><A HREF="autoconf.html#IDX269">HAVE_GETMNTENT</A>
<LI><A HREF="autoconf.html#IDX398">HAVE_<VAR>header</VAR></A>
<LI><A HREF="autoconf.html#IDX494">HAVE_LONG_DOUBLE</A>
<LI><A HREF="autoconf.html#IDX553">HAVE_LONG_FILE_NAMES</A>
<LI><A HREF="autoconf.html#IDX314">HAVE_LSTAT_EMPTY_STRING_BUG</A>
<LI><A HREF="autoconf.html#IDX293">HAVE_MMAP</A>
<LI><A HREF="autoconf.html#IDX371">HAVE_NDIR_H</A>
<LI><A HREF="autoconf.html#IDX297">HAVE_OBSTACK</A>
<LI><A HREF="autoconf.html#IDX975">HAVE_RESTARTABLE_SYSCALLS</A>
<LI><A HREF="autoconf.html#IDX412">HAVE_ST_BLKSIZE</A>
<LI><A HREF="autoconf.html#IDX416">HAVE_ST_BLOCKS</A>
<LI><A HREF="autoconf.html#IDX420">HAVE_ST_RDEV</A>
<LI><A HREF="autoconf.html#IDX313">HAVE_STAT_EMPTY_STRING_BUG</A>
<LI><A HREF="autoconf.html#IDX323">HAVE_STRCOLL</A>
<LI><A HREF="autoconf.html#IDX331">HAVE_STRERROR_R</A>
<LI><A HREF="autoconf.html#IDX337">HAVE_STRFTIME</A>
<LI><A HREF="autoconf.html#IDX497">HAVE_STRINGIZE</A>
<LI><A HREF="autoconf.html#IDX341">HAVE_STRNLEN</A>
<LI><A HREF="autoconf.html#IDX411">HAVE_STRUCT_STAT_ST_BLKSIZE</A>
<LI><A HREF="autoconf.html#IDX415">HAVE_STRUCT_STAT_ST_BLOCKS</A>
<LI><A HREF="autoconf.html#IDX421">HAVE_STRUCT_STAT_ST_RDEV</A>
<LI><A HREF="autoconf.html#IDX372">HAVE_SYS_DIR_H</A>
<LI><A HREF="autoconf.html#IDX373">HAVE_SYS_NDIR_H</A>
<LI><A HREF="autoconf.html#IDX386">HAVE_SYS_WAIT_H</A>
<LI><A HREF="autoconf.html#IDX427">HAVE_TM_ZONE</A>
<LI><A HREF="autoconf.html#IDX428">HAVE_TZNAME</A>
<LI><A HREF="autoconf.html#IDX345">HAVE_UTIME_NULL</A>
<LI><A HREF="autoconf.html#IDX237">HAVE_VFORK_H</A>
<LI><A HREF="autoconf.html#IDX349">HAVE_VPRINTF</A>
<LI><A HREF="autoconf.html#IDX855">HAVE_WAIT3</A>
<LI><A HREF="autoconf.html#IDX238">HAVE_WORKING_FORK</A>
<LI><A HREF="autoconf.html#IDX239">HAVE_WORKING_VFORK</A>
</DIR>
<H2><A NAME="cvindex_i">i</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX488">inline</A>
<LI><A HREF="autoconf.html#IDX880">INT_16_BITS</A>
</DIR>
<H2><A NAME="cvindex_l">l</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX899">LONG_64_BITS</A>
<LI><A HREF="autoconf.html#IDX278">LSTAT_FOLLOWS_SLASHED_SYMLINK</A>
</DIR>
<H2><A NAME="cvindex_m">m</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX376">MAJOR_IN_MKDEV</A>
<LI><A HREF="autoconf.html#IDX377">MAJOR_IN_SYSMACROS</A>
<LI><A HREF="autoconf.html#IDX438">mode_t</A>
</DIR>
<H2><A NAME="cvindex_n">n</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX837">NDIR</A>
<LI><A HREF="autoconf.html#IDX908">NEED_MEMORY_H</A>
<LI><A HREF="autoconf.html#IDX260">NEED_SETGID</A>
<LI><A HREF="autoconf.html#IDX258">NLIST_NAME_UNION</A>
<LI><A HREF="autoconf.html#IDX257">NLIST_STRUCT</A>
<LI><A HREF="autoconf.html#IDX469">NO_MINUS_C_MINUS_O</A>
</DIR>
<H2><A NAME="cvindex_o">o</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX441">off_t</A>
</DIR>
<H2><A NAME="cvindex_p">p</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX31">PACKAGE_BUGREPORT</A>
<LI><A HREF="autoconf.html#IDX19">PACKAGE_NAME</A>
<LI><A HREF="autoconf.html#IDX28">PACKAGE_STRING</A>
<LI><A HREF="autoconf.html#IDX22">PACKAGE_TARNAME</A>
<LI><A HREF="autoconf.html#IDX25">PACKAGE_VERSION</A>
<LI><A HREF="autoconf.html#IDX502">PARAMS</A>
<LI><A HREF="autoconf.html#IDX444">pid_t</A>
<LI><A HREF="autoconf.html#IDX500">PROTOTYPES</A>
</DIR>
<H2><A NAME="cvindex_r">r</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX447">RETSIGTYPE</A>
</DIR>
<H2><A NAME="cvindex_s">s</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX301">SELECT_TYPE_ARG1</A>
<LI><A HREF="autoconf.html#IDX302">SELECT_TYPE_ARG234</A>
<LI><A HREF="autoconf.html#IDX303">SELECT_TYPE_ARG5</A>
<LI><A HREF="autoconf.html#IDX307">SETPGRP_VOID</A>
<LI><A HREF="autoconf.html#IDX319">SETVBUF_REVERSED</A>
<LI><A HREF="autoconf.html#IDX450">size_t</A>
<LI><A HREF="autoconf.html#IDX383">STDC_HEADERS</A>
<LI><A HREF="autoconf.html#IDX333">STRERROR_R_CHAR_P</A>
<LI><A HREF="autoconf.html#IDX253">SVR4</A>
<LI><A HREF="autoconf.html#IDX402">SYS_SIGLIST_DECLARED</A>
<LI><A HREF="autoconf.html#IDX836">SYSDIR</A>
<LI><A HREF="autoconf.html#IDX835">SYSNDIR</A>
</DIR>
<H2><A NAME="cvindex_t">t</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX390">TIME_WITH_SYS_TIME</A>
<LI><A HREF="autoconf.html#IDX424">TM_IN_SYS_TIME</A>
</DIR>
<H2><A NAME="cvindex_u">u</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX453">uid_t</A>
<LI><A HREF="autoconf.html#IDX255">UMAX</A>
<LI><A HREF="autoconf.html#IDX256">UMAX4_3</A>
<LI><A HREF="autoconf.html#IDX992">USG</A>
</DIR>
<H2><A NAME="cvindex_v">v</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX240">vfork</A>
<LI><A HREF="autoconf.html#IDX485">volatile</A>
</DIR>
<H2><A NAME="cvindex_w">w</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX478">WORDS_BIGENDIAN</A>
</DIR>
<H2><A NAME="cvindex_x">x</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX543">X_DISPLAY_MISSING</A>
</DIR>
<H2><A NAME="cvindex_y">y</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX171">YYTEXT_POINTER</A>
</DIR>
<H2><A NAME="SEC187" HREF="autoconf_toc.html#TOC187">Autoconf Macro Index</A></H2>
<P>
This is an alphabetical list of the Autoconf macros. To make the list
easier to use, the macros are listed without their preceding <SAMP>`AC_'</SAMP>.
<P>
Jump to:
<A HREF="#acindex_a">a</A>
-
<A HREF="#acindex_b">b</A>
-
<A HREF="#acindex_c">c</A>
-
<A HREF="#acindex_d">d</A>
-
<A HREF="#acindex_e">e</A>
-
<A HREF="#acindex_f">f</A>
-
<A HREF="#acindex_g">g</A>
-
<A HREF="#acindex_h">h</A>
-
<A HREF="#acindex_i">i</A>
-
<A HREF="#acindex_l">l</A>
-
<A HREF="#acindex_m">m</A>
-
<A HREF="#acindex_o">o</A>
-
<A HREF="#acindex_p">p</A>
-
<A HREF="#acindex_r">r</A>
-
<A HREF="#acindex_s">s</A>
-
<A HREF="#acindex_t">t</A>
-
<A HREF="#acindex_u">u</A>
-
<A HREF="#acindex_v">v</A>
-
<A HREF="#acindex_w">w</A>
-
<A HREF="#acindex_x">x</A>
-
<A HREF="#acindex_y">y</A>
<P>
<H2><A NAME="acindex_a">a</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX138">AH_BOTTOM</A>
<LI><A HREF="autoconf.html#IDX132">AH_TEMPLATE</A>
<LI><A HREF="autoconf.html#IDX135">AH_TOP</A>
<LI><A HREF="autoconf.html#IDX129">AH_VERBATIM</A>
<LI><A HREF="autoconf.html#IDX559">AIX</A>
<LI><A HREF="autoconf.html#IDX809">ALLOCA</A>
<LI><A HREF="autoconf.html#IDX811">ARG_ARRAY</A>
<LI><A HREF="autoconf.html#IDX779">ARG_ENABLE</A>
<LI><A HREF="autoconf.html#IDX785">ARG_PROGRAM</A>
<LI><A HREF="autoconf.html#IDX603">ARG_VAR</A>
<LI><A HREF="autoconf.html#IDX775">ARG_WITH</A>
<LI><A HREF="autoconf.html#IDX684">AU_DEFUN</A>
</DIR>
<H2><A NAME="acindex_b">b</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX681">BEFORE</A>
<LI><A HREF="autoconf.html#IDX139">BOTTOM</A>
</DIR>
<H2><A NAME="acindex_c">c</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX477">C_BIGENDIAN</A>
<LI><A HREF="autoconf.html#IDX490">C_CHAR_UNSIGNED</A>
<LI><A HREF="autoconf.html#IDX481">C_CONST</A>
<LI><A HREF="autoconf.html#IDX813">C_CROSS</A>
<LI><A HREF="autoconf.html#IDX487">C_INLINE</A>
<LI><A HREF="autoconf.html#IDX493">C_LONG_DOUBLE</A>
<LI><A HREF="autoconf.html#IDX499">C_PROTOTYPES</A>
<LI><A HREF="autoconf.html#IDX496">C_STRINGIZE</A>
<LI><A HREF="autoconf.html#IDX484">C_VOLATILE</A>
<LI><A HREF="autoconf.html#IDX608">CACHE_CHECK</A>
<LI><A HREF="autoconf.html#IDX611">CACHE_LOAD</A>
<LI><A HREF="autoconf.html#IDX613">CACHE_SAVE</A>
<LI><A HREF="autoconf.html#IDX606">CACHE_VAL</A>
<LI><A HREF="autoconf.html#IDX757">CANONICAL_BUILD</A>
<LI><A HREF="autoconf.html#IDX763">CANONICAL_HOST</A>
<LI><A HREF="autoconf.html#IDX815">CANONICAL_SYSTEM</A>
<LI><A HREF="autoconf.html#IDX769">CANONICAL_TARGET</A>
<LI><A HREF="autoconf.html#IDX817">CHAR_UNSIGNED</A>
<LI><A HREF="autoconf.html#IDX404">CHECK_DECL</A>
<LI><A HREF="autoconf.html#IDX406">CHECK_DECLS</A>
<LI><A HREF="autoconf.html#IDX198">CHECK_FILE</A>
<LI><A HREF="autoconf.html#IDX200">CHECK_FILES</A>
<LI><A HREF="autoconf.html#IDX353">CHECK_FUNC</A>
<LI><A HREF="autoconf.html#IDX355">CHECK_FUNCS</A>
<LI><A HREF="autoconf.html#IDX395">CHECK_HEADER</A>
<LI><A HREF="autoconf.html#IDX397">CHECK_HEADERS</A>
<LI><A HREF="autoconf.html#IDX203">CHECK_LIB</A>
<LI><A HREF="autoconf.html#IDX430">CHECK_MEMBER</A>
<LI><A HREF="autoconf.html#IDX432">CHECK_MEMBERS</A>
<LI><A HREF="autoconf.html#IDX183">CHECK_PROG</A>
<LI><A HREF="autoconf.html#IDX185">CHECK_PROGS</A>
<LI><A HREF="autoconf.html#IDX462">CHECK_SIZEOF</A>
<LI><A HREF="autoconf.html#IDX187">CHECK_TOOL</A>
<LI><A HREF="autoconf.html#IDX189">CHECK_TOOLS</A>
<LI><A HREF="autoconf.html#IDX456">CHECK_TYPE</A>, <A HREF="autoconf.html#IDX819">CHECK_TYPE</A>
<LI><A HREF="autoconf.html#IDX458">CHECK_TYPES</A>
<LI><A HREF="autoconf.html#IDX821">CHECKING</A>
<LI><A HREF="autoconf.html#IDX823">COMPILE_CHECK</A>
<LI><A HREF="autoconf.html#IDX44">CONFIG_AUX_DIR</A>
<LI><A HREF="autoconf.html#IDX141">CONFIG_COMMANDS</A>
<LI><A HREF="autoconf.html#IDX52">CONFIG_FILES</A>
<LI><A HREF="autoconf.html#IDX122">CONFIG_HEADERS</A>
<LI><A HREF="autoconf.html#IDX147">CONFIG_LINKS</A>
<LI><A HREF="autoconf.html#IDX42">CONFIG_SRCDIR</A>
<LI><A HREF="autoconf.html#IDX150">CONFIG_SUBDIRS</A>
<LI><A HREF="autoconf.html#IDX825">CONST</A>
<LI><A HREF="autoconf.html#IDX36">COPYRIGHT</A>
<LI><A HREF="autoconf.html#IDX827">CROSS_CHECK</A>
<LI><A HREF="autoconf.html#IDX829">CYGWIN</A>
</DIR>
<H2><A NAME="acindex_d">d</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX401">DECL_SYS_SIGLIST</A>
<LI><A HREF="autoconf.html#IDX831">DECL_YYTEXT</A>
<LI><A HREF="autoconf.html#IDX593">DEFINE</A>
<LI><A HREF="autoconf.html#IDX595">DEFINE_UNQUOTED</A>
<LI><A HREF="autoconf.html#IDX669">DEFUN</A>, <A HREF="autoconf.html#IDX683">DEFUN</A>
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<H2><A NAME="acindex_e">e</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX574">EGREP_CPP</A>
<LI><A HREF="autoconf.html#IDX572">EGREP_HEADER</A>
<LI><A HREF="autoconf.html#IDX844">EMXOS2</A>
<LI><A HREF="autoconf.html#IDX781">ENABLE</A>
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<H2><A NAME="acindex_f">f</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX524">F77_DUMMY_MAIN</A>
<LI><A HREF="autoconf.html#IDX534">F77_FUNC</A>
<LI><A HREF="autoconf.html#IDX521">F77_LIBRARY_LDFLAGS</A>
<LI><A HREF="autoconf.html#IDX527">F77_MAIN</A>
<LI><A HREF="autoconf.html#IDX530">F77_WRAPPERS</A>
<LI><A HREF="autoconf.html#IDX677">FATAL</A>
<LI><A HREF="autoconf.html#IDX848">FIND_X</A>
<LI><A HREF="autoconf.html#IDX850">FIND_XTRA</A>
<LI><A HREF="autoconf.html#IDX217">FUNC_ALLOCA</A>
<LI><A HREF="autoconf.html#IDX852">FUNC_CHECK</A>
<LI><A HREF="autoconf.html#IDX223">FUNC_CHOWN</A>
<LI><A HREF="autoconf.html#IDX226">FUNC_CLOSEDIR_VOID</A>
<LI><A HREF="autoconf.html#IDX230">FUNC_ERROR_AT_LINE</A>
<LI><A HREF="autoconf.html#IDX233">FUNC_FNMATCH</A>
<LI><A HREF="autoconf.html#IDX236">FUNC_FORK</A>
<LI><A HREF="autoconf.html#IDX244">FUNC_FSEEKO</A>
<LI><A HREF="autoconf.html#IDX248">FUNC_GETGROUPS</A>
<LI><A HREF="autoconf.html#IDX252">FUNC_GETLOADAVG</A>
<LI><A HREF="autoconf.html#IDX268">FUNC_GETMNTENT</A>
<LI><A HREF="autoconf.html#IDX272">FUNC_GETPGRP</A>
<LI><A HREF="autoconf.html#IDX312">FUNC_LSTAT</A>
<LI><A HREF="autoconf.html#IDX277">FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK</A>
<LI><A HREF="autoconf.html#IDX281">FUNC_MALLOC</A>
<LI><A HREF="autoconf.html#IDX284">FUNC_MEMCMP</A>
<LI><A HREF="autoconf.html#IDX288">FUNC_MKTIME</A>
<LI><A HREF="autoconf.html#IDX292">FUNC_MMAP</A>
<LI><A HREF="autoconf.html#IDX296">FUNC_OBSTACK</A>
<LI><A HREF="autoconf.html#IDX300">FUNC_SELECT_ARGTYPES</A>
<LI><A HREF="autoconf.html#IDX306">FUNC_SETPGRP</A>
<LI><A HREF="autoconf.html#IDX318">FUNC_SETVBUF_REVERSED</A>
<LI><A HREF="autoconf.html#IDX311">FUNC_STAT</A>
<LI><A HREF="autoconf.html#IDX322">FUNC_STRCOLL</A>
<LI><A HREF="autoconf.html#IDX330">FUNC_STRERROR_R</A>
<LI><A HREF="autoconf.html#IDX336">FUNC_STRFTIME</A>
<LI><A HREF="autoconf.html#IDX340">FUNC_STRNLEN</A>
<LI><A HREF="autoconf.html#IDX326">FUNC_STRTOD</A>
<LI><A HREF="autoconf.html#IDX344">FUNC_UTIME_NULL</A>
<LI><A HREF="autoconf.html#IDX348">FUNC_VPRINTF</A>
<LI><A HREF="autoconf.html#IDX854">FUNC_WAIT3</A>
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<H2><A NAME="acindex_g">g</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX857">GCC_TRADITIONAL</A>
<LI><A HREF="autoconf.html#IDX859">GETGROUPS_T</A>
<LI><A HREF="autoconf.html#IDX861">GETLOADAVG</A>
</DIR>
<H2><A NAME="acindex_h">h</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX863">HAVE_FUNCS</A>
<LI><A HREF="autoconf.html#IDX865">HAVE_HEADERS</A>
<LI><A HREF="autoconf.html#IDX867">HAVE_LIBRARY</A>
<LI><A HREF="autoconf.html#IDX869">HAVE_POUNDBANG</A>
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<LI><A HREF="autoconf.html#IDX369">HEADER_DIRENT</A>
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<LI><A HREF="autoconf.html#IDX375">HEADER_MAJOR</A>
<LI><A HREF="autoconf.html#IDX379">HEADER_STAT</A>
<LI><A HREF="autoconf.html#IDX382">HEADER_STDC</A>
<LI><A HREF="autoconf.html#IDX385">HEADER_SYS_WAIT</A>
<LI><A HREF="autoconf.html#IDX389">HEADER_TIME</A>
<LI><A HREF="autoconf.html#IDX392">HEADER_TIOCGWINSZ</A>
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<H2><A NAME="acindex_i">i</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX16">INIT</A>, <A HREF="autoconf.html#IDX875">INIT</A>
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<LI><A HREF="autoconf.html#IDX879">INT_16_BITS</A>
<LI><A HREF="autoconf.html#IDX882">IRIX_SUN</A>
<LI><A HREF="autoconf.html#IDX562">ISC_POSIX</A>
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<H2><A NAME="acindex_l">l</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX884">LANG_C</A>
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<LI><A HREF="autoconf.html#IDX888">LANG_FORTRAN77</A>
<LI><A HREF="autoconf.html#IDX589">LANG_POP</A>
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<LI><A HREF="autoconf.html#IDX890">LANG_RESTORE</A>
<LI><A HREF="autoconf.html#IDX892">LANG_SAVE</A>
<LI><A HREF="autoconf.html#IDX358">LIBOBJ</A>
<LI><A HREF="autoconf.html#IDX361">LIBSOURCE</A>
<LI><A HREF="autoconf.html#IDX363">LIBSOURCES</A>
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<LI><A HREF="autoconf.html#IDX898">LONG_64_BITS</A>
<LI><A HREF="autoconf.html#IDX901">LONG_DOUBLE</A>
<LI><A HREF="autoconf.html#IDX903">LONG_FILE_NAMES</A>
</DIR>
<H2><A NAME="acindex_m">m</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX905">MAJOR_HEADER</A>
<LI><A HREF="autoconf.html#IDX907">MEMORY_H</A>
<LI><A HREF="autoconf.html#IDX910">MINGW32</A>
<LI><A HREF="autoconf.html#IDX565">MINIX</A>
<LI><A HREF="autoconf.html#IDX912">MINUS_C_MINUS_O</A>
<LI><A HREF="autoconf.html#IDX914">MMAP</A>
<LI><A HREF="autoconf.html#IDX916">MODE_T</A>
<LI><A HREF="autoconf.html#IDX616">MSG_CHECKING</A>
<LI><A HREF="autoconf.html#IDX622">MSG_ERROR</A>
<LI><A HREF="autoconf.html#IDX620">MSG_NOTICE</A>
<LI><A HREF="autoconf.html#IDX618">MSG_RESULT</A>
<LI><A HREF="autoconf.html#IDX624">MSG_WARN</A>
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<H2><A NAME="acindex_o">o</A></H2>
<DIR>
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<LI><A HREF="autoconf.html#IDX921">OBSOLETE</A>
<LI><A HREF="autoconf.html#IDX923">OFF_T</A>
<LI><A HREF="autoconf.html#IDX46">OUTPUT</A>, <A HREF="autoconf.html#IDX925">OUTPUT</A>
<LI><A HREF="autoconf.html#IDX927">OUTPUT_COMMANDS</A>
<LI><A HREF="autoconf.html#IDX145">OUTPUT_COMMANDS_POST</A>
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<H2><A NAME="acindex_p">p</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX29">PACKAGE_BUGREPORT</A>
<LI><A HREF="autoconf.html#IDX17">PACKAGE_NAME</A>
<LI><A HREF="autoconf.html#IDX26">PACKAGE_STRING</A>
<LI><A HREF="autoconf.html#IDX20">PACKAGE_TARNAME</A>
<LI><A HREF="autoconf.html#IDX23">PACKAGE_VERSION</A>
<LI><A HREF="autoconf.html#IDX191">PATH_PROG</A>
<LI><A HREF="autoconf.html#IDX193">PATH_PROGS</A>
<LI><A HREF="autoconf.html#IDX195">PATH_TOOL</A>
<LI><A HREF="autoconf.html#IDX536">PATH_X</A>
<LI><A HREF="autoconf.html#IDX538">PATH_XTRA</A>
<LI><A HREF="autoconf.html#IDX929">PID_T</A>
<LI><A HREF="autoconf.html#IDX931">PREFIX</A>
<LI><A HREF="autoconf.html#IDX153">PREFIX_DEFAULT</A>
<LI><A HREF="autoconf.html#IDX155">PREFIX_PROGRAM</A>
<LI><A HREF="autoconf.html#IDX33">PREREQ</A>
<LI><A HREF="autoconf.html#IDX159">PROG_AWK</A>
<LI><A HREF="autoconf.html#IDX464">PROG_CC</A>
<LI><A HREF="autoconf.html#IDX468">PROG_CC_C_O</A>
<LI><A HREF="autoconf.html#IDX471">PROG_CC_STDC</A>
<LI><A HREF="autoconf.html#IDX474">PROG_CPP</A>
<LI><A HREF="autoconf.html#IDX507">PROG_CXX</A>
<LI><A HREF="autoconf.html#IDX511">PROG_CXXCPP</A>
<LI><A HREF="autoconf.html#IDX518">PROG_F77_C_O</A>
<LI><A HREF="autoconf.html#IDX514">PROG_FORTRAN</A>
<LI><A HREF="autoconf.html#IDX504">PROG_GCC_TRADITIONAL</A>
<LI><A HREF="autoconf.html#IDX162">PROG_INSTALL</A>
<LI><A HREF="autoconf.html#IDX168">PROG_LEX</A>
<LI><A HREF="autoconf.html#IDX174">PROG_LN_S</A>
<LI><A HREF="autoconf.html#IDX49">PROG_MAKE_SET</A>
<LI><A HREF="autoconf.html#IDX177">PROG_RANLIB</A>
<LI><A HREF="autoconf.html#IDX180">PROG_YACC</A>
<LI><A HREF="autoconf.html#IDX937">PROGRAM_CHECK</A>
<LI><A HREF="autoconf.html#IDX939">PROGRAM_EGREP</A>
<LI><A HREF="autoconf.html#IDX941">PROGRAM_PATH</A>
<LI><A HREF="autoconf.html#IDX933">PROGRAMS_CHECK</A>
<LI><A HREF="autoconf.html#IDX935">PROGRAMS_PATH</A>
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<H2><A NAME="acindex_r">r</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX943">REMOTE_TAPE</A>
<LI><A HREF="autoconf.html#IDX365">REPLACE_FUNCS</A>
<LI><A HREF="autoconf.html#IDX679">REQUIRE</A>
<LI><A HREF="autoconf.html#IDX591">REQUIRE_CPP</A>
<LI><A HREF="autoconf.html#IDX945">RESTARTABLE_SYSCALLS</A>
<LI><A HREF="autoconf.html#IDX947">RETSIGTYPE</A>
<LI><A HREF="autoconf.html#IDX39">REVISION</A>
<LI><A HREF="autoconf.html#IDX949">RSH</A>
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<H2><A NAME="acindex_s">s</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX951">SCO_INTL</A>
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<LI><A HREF="autoconf.html#IDX956">SET_MAKE</A>
<LI><A HREF="autoconf.html#IDX954">SETVBUF_REVERSED</A>
<LI><A HREF="autoconf.html#IDX960">SIZE_T</A>
<LI><A HREF="autoconf.html#IDX958">SIZEOF_TYPE</A>
<LI><A HREF="autoconf.html#IDX968">ST_BLKSIZE</A>
<LI><A HREF="autoconf.html#IDX970">ST_BLOCKS</A>
<LI><A HREF="autoconf.html#IDX972">ST_RDEV</A>
<LI><A HREF="autoconf.html#IDX380">STAT_MACROS_BROKEN</A>, <A HREF="autoconf.html#IDX962">STAT_MACROS_BROKEN</A>
<LI><A HREF="autoconf.html#IDX964">STDC_HEADERS</A>
<LI><A HREF="autoconf.html#IDX966">STRCOLL</A>
<LI><A HREF="autoconf.html#IDX410">STRUCT_ST_BLKSIZE</A>
<LI><A HREF="autoconf.html#IDX414">STRUCT_ST_BLOCKS</A>
<LI><A HREF="autoconf.html#IDX419">STRUCT_ST_RDEV</A>
<LI><A HREF="autoconf.html#IDX426">STRUCT_TIMEZONE</A>
<LI><A HREF="autoconf.html#IDX423">STRUCT_TM</A>
<LI><A HREF="autoconf.html#IDX597">SUBST</A>
<LI><A HREF="autoconf.html#IDX599">SUBST_FILE</A>
<LI><A HREF="autoconf.html#IDX545">SYS_INTERPRETER</A>
<LI><A HREF="autoconf.html#IDX547">SYS_LARGEFILE</A>
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<LI><A HREF="autoconf.html#IDX555">SYS_POSIX_TERMIOS</A>
<LI><A HREF="autoconf.html#IDX974">SYS_RESTARTABLE_SYSCALLS</A>
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<H2><A NAME="acindex_t">t</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX133">TEMPLATE</A>
<LI><A HREF="autoconf.html#IDX979">TEST_CPP</A>
<LI><A HREF="autoconf.html#IDX981">TEST_PROGRAM</A>
<LI><A HREF="autoconf.html#IDX985">TIME_WITH_SYS_TIME</A>
<LI><A HREF="autoconf.html#IDX983">TIMEZONE</A>
<LI><A HREF="autoconf.html#IDX136">TOP</A>
<LI><A HREF="autoconf.html#IDX576">TRY_COMPILE</A>
<LI><A HREF="autoconf.html#IDX570">TRY_CPP</A>
<LI><A HREF="autoconf.html#IDX578">TRY_LINK</A>
<LI><A HREF="autoconf.html#IDX580">TRY_LINK_FUNC</A>
<LI><A HREF="autoconf.html#IDX582">TRY_RUN</A>
<LI><A HREF="autoconf.html#IDX434">TYPE_GETGROUPS</A>
<LI><A HREF="autoconf.html#IDX437">TYPE_MODE_T</A>
<LI><A HREF="autoconf.html#IDX440">TYPE_OFF_T</A>
<LI><A HREF="autoconf.html#IDX443">TYPE_PID_T</A>
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<H2><A NAME="acindex_u">u</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX987">UID_T</A>
<LI><A HREF="autoconf.html#IDX989">UNISTD_H</A>
<LI><A HREF="autoconf.html#IDX991">USG</A>
<LI><A HREF="autoconf.html#IDX994">UTIME_NULL</A>
</DIR>
<H2><A NAME="acindex_v">v</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX996">VALIDATE_CACHED_SYSTEM_TUPLE</A>
<LI><A HREF="autoconf.html#IDX130">VERBATIM</A>
<LI><A HREF="autoconf.html#IDX998">VERBOSE</A>
<LI><A HREF="autoconf.html#IDX1000">VFORK</A>
<LI><A HREF="autoconf.html#IDX1002">VPRINTF</A>
</DIR>
<H2><A NAME="acindex_w">w</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX1004">WAIT3</A>
<LI><A HREF="autoconf.html#IDX1006">WARN</A>
<LI><A HREF="autoconf.html#IDX675">WARNING</A>
<LI><A HREF="autoconf.html#IDX777">WITH</A>
<LI><A HREF="autoconf.html#IDX1008">WORDS_BIGENDIAN</A>
</DIR>
<H2><A NAME="acindex_x">x</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX1010">XENIX_DIR</A>
</DIR>
<H2><A NAME="acindex_y">y</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX1013">YYTEXT_POINTER</A>
</DIR>
<H2><A NAME="SEC188" HREF="autoconf_toc.html#TOC188">M4 Macro Index</A></H2>
<P>
This is an alphabetical list of the M4, M4sugar, and M4sh macros. To
make the list easier to use, the macros are listed without their
preceding <SAMP>`m4_'</SAMP> or <SAMP>`AS_'</SAMP>.
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Jump to:
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<P>
<H2><A NAME="msindex_b">b</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX652">bpatsubst</A>
<LI><A HREF="autoconf.html#IDX656">bregexp</A>
</DIR>
<H2><A NAME="msindex_d">d</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX642">defn</A>, <A HREF="autoconf.html#IDX654">defn</A>
<LI><A HREF="autoconf.html#IDX668">DIRNAME</A>
<LI><A HREF="autoconf.html#IDX640">dnl</A>
<LI><A HREF="autoconf.html#IDX660">dquote</A>
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<H2><A NAME="msindex_m">m</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX644">m4_exit</A>
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<LI><A HREF="autoconf.html#IDX658">m4_wrap</A>
</DIR>
<H2><A NAME="msindex_p">p</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX666">pattern_allow</A>
<LI><A HREF="autoconf.html#IDX664">pattern_forbid</A>
</DIR>
<H2><A NAME="msindex_q">q</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX662">quote</A>
</DIR>
<H2><A NAME="msindex_u">u</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX650">undefine</A>
</DIR>
<H2><A NAME="SEC189" HREF="autoconf_toc.html#TOC189">Autotest Macro Index</A></H2>
<P>
This is an alphabetical list of the Autotest macros. To make the list
easier to use, the macros are listed without their preceding <SAMP>`AT_'</SAMP>.
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<P>
<H2><A NAME="atindex_c">c</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX1031">CHECK</A>
<LI><A HREF="autoconf.html#IDX1027">CLEANUP</A>
</DIR>
<H2><A NAME="atindex_d">d</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX1029">DATA</A>
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<H2><A NAME="atindex_i">i</A></H2>
<DIR>
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<DIR>
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<DIR>
<LI><A HREF="autoconf.html#IDX1021">TESTED</A>
</DIR>
<H2><A NAME="SEC190" HREF="autoconf_toc.html#TOC190">Program and Function Index</A></H2>
<P>
This is an alphabetical list of the programs and functions which
portability is discussed in this document.
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<P>
<H2><A NAME="prindex_@">@</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX714">@command{!}</A>
<LI><A HREF="autoconf.html#IDX713">@command{.}</A>
<LI><A HREF="autoconf.html#IDX689">@command{/usr/xpg4/bin/sh} on Solaris</A>
<LI><A HREF="autoconf.html#IDX729">@command{:}</A>
<LI><A HREF="autoconf.html#IDX731">@command{awk}</A>
<LI><A HREF="autoconf.html#IDX715">@command{break}</A>
<LI><A HREF="autoconf.html#IDX716">@command{case}</A>
<LI><A HREF="autoconf.html#IDX732">@command{cat}</A>
<LI><A HREF="autoconf.html#IDX733">@command{cmp}</A>
<LI><A HREF="autoconf.html#IDX734">@command{cp}</A>
<LI><A HREF="autoconf.html#IDX735">@command{date}</A>
<LI><A HREF="autoconf.html#IDX736">@command{diff}</A>
<LI><A HREF="autoconf.html#IDX737">@command{dirname}</A>
<LI><A HREF="autoconf.html#IDX717">@command{echo}</A>
<LI><A HREF="autoconf.html#IDX738">@command{egrep}</A>
<LI><A HREF="autoconf.html#IDX718">@command{exit}</A>
<LI><A HREF="autoconf.html#IDX719">@command{export}</A>
<LI><A HREF="autoconf.html#IDX739">@command{expr}</A>, <A HREF="autoconf.html#IDX741">@command{expr}</A>
<LI><A HREF="autoconf.html#IDX740">@command{expr} (<SAMP>`|'</SAMP>)</A>
<LI><A HREF="autoconf.html#IDX720">@command{false}</A>
<LI><A HREF="autoconf.html#IDX721">@command{for}</A>
<LI><A HREF="autoconf.html#IDX742">@command{grep}</A>
<LI><A HREF="autoconf.html#IDX722">@command{if}</A>
<LI><A HREF="autoconf.html#IDX743">@command{ln}</A>
<LI><A HREF="autoconf.html#IDX745">@command{mv}</A>
<LI><A HREF="autoconf.html#IDX747">@command{sed}</A>
<LI><A HREF="autoconf.html#IDX748">@command{sed} (<SAMP>`t'</SAMP>)</A>
<LI><A HREF="autoconf.html#IDX723">@command{set}</A>
<LI><A HREF="autoconf.html#IDX724">@command{shift}</A>
<LI><A HREF="autoconf.html#IDX725">@command{source}</A>
<LI><A HREF="autoconf.html#IDX726">@command{test}</A>
<LI><A HREF="autoconf.html#IDX749">@command{touch}</A>
<LI><A HREF="autoconf.html#IDX727">@command{trap}</A>
<LI><A HREF="autoconf.html#IDX728">@command{true}</A>
<LI><A HREF="autoconf.html#IDX730">@command{unset}</A>
</DIR>
<H2><A NAME="prindex_a">a</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX221"><CODE>alloca</CODE></A>
</DIR>
<H2><A NAME="prindex_c">c</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX224"><CODE>chown</CODE></A>
<LI><A HREF="autoconf.html#IDX228"><CODE>closedir</CODE></A>
</DIR>
<H2><A NAME="prindex_e">e</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX231"><CODE>error_at_line</CODE></A>
</DIR>
<H2><A NAME="prindex_f">f</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX234"><CODE>fnmatch</CODE></A>
<LI><A HREF="autoconf.html#IDX241"><CODE>fork</CODE></A>
<LI><A HREF="autoconf.html#IDX246"><CODE>fseeko</CODE></A>
</DIR>
<H2><A NAME="prindex_g">g</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX250"><CODE>getgroups</CODE></A>
<LI><A HREF="autoconf.html#IDX266"><CODE>getloadavg</CODE></A>
<LI><A HREF="autoconf.html#IDX270"><CODE>getmntent</CODE></A>
<LI><A HREF="autoconf.html#IDX274"><CODE>getpgid</CODE></A>
<LI><A HREF="autoconf.html#IDX275"><CODE>getpgrp</CODE></A>
</DIR>
<H2><A NAME="prindex_l">l</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX279"><CODE>lstat</CODE></A>, <A HREF="autoconf.html#IDX316"><CODE>lstat</CODE></A>
</DIR>
<H2><A NAME="prindex_m">m</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX282"><CODE>malloc</CODE></A>
<LI><A HREF="autoconf.html#IDX286"><CODE>memcmp</CODE></A>
<LI><A HREF="autoconf.html#IDX290"><CODE>mktime</CODE></A>
<LI><A HREF="autoconf.html#IDX294"><CODE>mmap</CODE></A>
</DIR>
<H2><A NAME="prindex_s">s</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX304"><CODE>select</CODE></A>
<LI><A HREF="autoconf.html#IDX308"><CODE>setpgrp</CODE></A>
<LI><A HREF="autoconf.html#IDX320"><CODE>setvbuf</CODE></A>
<LI><A HREF="autoconf.html#IDX206"><CODE>snprintf</CODE></A>
<LI><A HREF="autoconf.html#IDX208"><CODE>sprintf</CODE></A>
<LI><A HREF="autoconf.html#IDX210"><CODE>sscanf</CODE></A>
<LI><A HREF="autoconf.html#IDX315"><CODE>stat</CODE></A>
<LI><A HREF="autoconf.html#IDX324"><CODE>strcoll</CODE></A>
<LI><A HREF="autoconf.html#IDX334"><CODE>strerror_r</CODE></A>
<LI><A HREF="autoconf.html#IDX338"><CODE>strftime</CODE></A>
<LI><A HREF="autoconf.html#IDX211"><CODE>strnlen</CODE></A>, <A HREF="autoconf.html#IDX342"><CODE>strnlen</CODE></A>
<LI><A HREF="autoconf.html#IDX328"><CODE>strtod</CODE></A>
</DIR>
<H2><A NAME="prindex_u">u</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX212"><CODE>unlink</CODE></A>
<LI><A HREF="autoconf.html#IDX346"><CODE>utime</CODE></A>
</DIR>
<H2><A NAME="prindex_v">v</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX213"><CODE>va_copy</CODE></A>
<LI><A HREF="autoconf.html#IDX214"><CODE>va_list</CODE></A>
<LI><A HREF="autoconf.html#IDX242"><CODE>vfork</CODE></A>
<LI><A HREF="autoconf.html#IDX351"><CODE>vprintf</CODE></A>
<LI><A HREF="autoconf.html#IDX207"><CODE>vsnprintf</CODE></A>
<LI><A HREF="autoconf.html#IDX209"><CODE>vsprintf</CODE></A>
</DIR>
<H2><A NAME="SEC191" HREF="autoconf_toc.html#TOC191">Concept Index</A></H2>
<P>
This is an alphabetical list of the files, tools, and concepts
introduced in this document.
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<A HREF="#cindex_a">a</A>
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<A HREF="#cindex_b">b</A>
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<A HREF="#cindex_c">c</A>
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<A HREF="#cindex_d">d</A>
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<H2><A NAME="cindex_"">"</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX691"><SAMP>`"$@"'</SAMP></A>
</DIR>
<H2><A NAME="cindex_$">$</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX697">$(<VAR>commands</VAR>)</A>
<LI><A HREF="autoconf.html#IDX692">${<VAR>var</VAR>:-<VAR>value</VAR>}</A>
<LI><A HREF="autoconf.html#IDX694">${<VAR>var</VAR>=<VAR>expanded-value</VAR>}</A>
<LI><A HREF="autoconf.html#IDX693">${<VAR>var</VAR>=<VAR>literal</VAR>}</A>
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<H2><A NAME="cindex_@">@</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX630"><SAMP>`@%:@'</SAMP></A>
<LI><A HREF="autoconf.html#IDX631"><SAMP>`@&t@'</SAMP></A>
<LI><A HREF="autoconf.html#IDX628"><SAMP>`@:>@'</SAMP></A>
<LI><A HREF="autoconf.html#IDX627"><SAMP>`@<:@'</SAMP></A>
<LI><A HREF="autoconf.html#IDX10">@command{autoconf}</A>
<LI><A HREF="autoconf.html#IDX126">@command{autoheader}</A>
<LI><A HREF="autoconf.html#IDX14">@command{autoreconf}</A>
<LI><A HREF="autoconf.html#IDX8">@command{autoscan}</A>
<LI><A HREF="autoconf.html#IDX806">@command{autoupdate}</A>
<LI><A HREF="autoconf.html#IDX790">@command{config.status}</A>
<LI><A HREF="autoconf.html#IDX752">@command{config.sub}</A>
<LI><A HREF="autoconf.html#IDX4">@command{configure}</A>, <A HREF="autoconf.html#IDX788">@command{configure}</A>
<LI><A HREF="autoconf.html#IDX9">@command{ifnames}</A>
<LI><A HREF="autoconf.html#IDX1016">@command{testsuite}</A>, <A HREF="autoconf.html#IDX1032">@command{testsuite}</A>
<LI><A HREF="autoconf.html#IDX629"><SAMP>`@S|@'</SAMP></A>
</DIR>
<H2><A NAME="cindex_`">`</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX695">`<VAR>commands</VAR>`</A>
</DIR>
<H2><A NAME="cindex_a">a</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX803"><TT>`acconfig.h'</TT></A>
<LI><A HREF="autoconf.html#IDX3"><TT>`aclocal.m4'</TT></A>
<LI><A HREF="autoconf.html#IDX686">Ash</A>
<LI><A HREF="autoconf.html#IDX636">Autom4te Library</A>
<LI><A HREF="autoconf.html#IDX635"><TT>`autom4te.cache'</TT></A>
<LI><A HREF="autoconf.html#IDX637"><TT>`autom4te.cfg'</TT></A>
<LI><A HREF="autoconf.html#IDX1">Automake</A>
<LI><A HREF="autoconf.html#IDX1015">Autotest</A>
<LI><A HREF="autoconf.html#IDX1033"><CODE>AUTOTEST_PATH</CODE></A>
</DIR>
<H2><A NAME="cindex_b">b</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX12">Back trace</A>, <A HREF="autoconf.html#IDX633">Back trace</A>
<LI><A HREF="autoconf.html#IDX687">Bash</A>
<LI><A HREF="autoconf.html#IDX688">Bash 2.05 and later</A>
</DIR>
<H2><A NAME="cindex_c">c</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX604">Cache</A>
<LI><A HREF="autoconf.html#IDX609">Cache variable</A>
<LI><A HREF="autoconf.html#IDX789">Cache, enabling</A>
<LI><A HREF="autoconf.html#IDX696">Command Substitution</A>
<LI><A HREF="autoconf.html#IDX120"><TT>`config.h'</TT></A>
<LI><A HREF="autoconf.html#IDX805"><TT>`config.h.bot'</TT></A>
<LI><A HREF="autoconf.html#IDX125"><TT>`config.h.in'</TT></A>
<LI><A HREF="autoconf.html#IDX804"><TT>`config.h.top'</TT></A>
<LI><A HREF="autoconf.html#IDX119">Configuration Header</A>
<LI><A HREF="autoconf.html#IDX124">Configuration Header Template</A>
<LI><A HREF="autoconf.html#IDX6"><TT>`configure.ac'</TT></A>
<LI><A HREF="autoconf.html#IDX5"><TT>`configure.in'</TT></A>
<LI><A HREF="autoconf.html#IDX37">Copyright Notice</A>
</DIR>
<H2><A NAME="cindex_d">d</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX399">Declaration, checking</A>
<LI><A HREF="autoconf.html#IDX670"><CODE>dnl</CODE></A>, <A HREF="autoconf.html#IDX685"><CODE>dnl</CODE></A>
</DIR>
<H2><A NAME="cindex_e">e</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX479">Endianness</A>
</DIR>
<H2><A NAME="cindex_f">f</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX1035">FDL, GNU Free Documentation License</A>
<LI><A HREF="autoconf.html#IDX196">File, checking</A>
<LI><A HREF="autoconf.html#IDX215">Function, checking</A>
</DIR>
<H2><A NAME="cindex_h">h</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX367">Header, checking</A>
</DIR>
<H2><A NAME="cindex_i">i</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX156">Includes, default</A>
<LI><A HREF="autoconf.html#IDX47">Instantiation</A>
</DIR>
<H2><A NAME="cindex_l">l</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX584">Language</A>
<LI><A HREF="autoconf.html#IDX201">Library, checking</A>
<LI><A HREF="autoconf.html#IDX2">Libtool</A>
<LI><A HREF="autoconf.html#IDX148">Links</A>
</DIR>
<H2><A NAME="cindex_m">m</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX638">M4sugar</A>
<LI><A HREF="autoconf.html#IDX13">Macro invocation stack</A>, <A HREF="autoconf.html#IDX634">Macro invocation stack</A>
<LI><A HREF="autoconf.html#IDX671">Messages, from @command{autoconf}</A>
<LI><A HREF="autoconf.html#IDX614">Messages, from @command{configure}</A>
<LI><A HREF="autoconf.html#IDX746">Moving open files</A>
</DIR>
<H2><A NAME="cindex_o">o</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX298">obstack</A>
</DIR>
<H2><A NAME="cindex_p">p</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX1034"><TT>`package.m4'</TT></A>
<LI><A HREF="autoconf.html#IDX556">POSIX termios headers</A>
<LI><A HREF="autoconf.html#IDX600">Previous Variable</A>
<LI><A HREF="autoconf.html#IDX157">Programs, checking</A>
</DIR>
<H2><A NAME="cindex_q">q</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX583">QNX 4.25</A>
<LI><A HREF="autoconf.html#IDX626">quadrigraphs</A>
<LI><A HREF="autoconf.html#IDX7">quotation</A>, <A HREF="autoconf.html#IDX625">quotation</A>
</DIR>
<H2><A NAME="cindex_r">r</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX40">Revision</A>
</DIR>
<H2><A NAME="cindex_s">s</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX408">Structure, checking</A>
<LI><A HREF="autoconf.html#IDX744">Symbolic links</A>
</DIR>
<H2><A NAME="cindex_t">t</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX557">termios POSIX headers</A>
<LI><A HREF="autoconf.html#IDX1017">test group</A>
</DIR>
<H2><A NAME="cindex_u">u</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX1014"><CODE>undefined macro: _m4_divert_diversion</CODE></A>
</DIR>
<H2><A NAME="cindex_v">v</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX601">Variable, Precious</A>
<LI><A HREF="autoconf.html#IDX34">Version</A>
<LI><A HREF="autoconf.html#IDX750"><CODE>VPATH</CODE></A>
</DIR>
<H2><A NAME="cindex_z">z</A></H2>
<DIR>
<LI><A HREF="autoconf.html#IDX690">Zsh</A>
</DIR>
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