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Autoconf Macro: ac_prototype
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<h1>
ac_prototype
</h1>
<h2>
SYNOPSIS
</h2>
<p class="indent" style="white-space:nowrap;">
<code>AC_PROTOTYPE(function, includes, code, TAG1, values1 [, TAG2, values2
[...]])</code>
</p>
<h2>
DESCRIPTION
</h2>
<div class="indent">
<p>
Try all the combinations of <TAG1>, <TAG2>... to successfully
compile <code>. <TAG1>, <TAG2>, ... are substituted in
<code> and <include> with values found in <values1>,
<values2>, ... respectively. <values1>, <values2>, ...
contain a list of possible values for each corresponding tag and all
combinations are tested. When AC_TRY_COMPILE(include, code) is successfull
for a given substitution, the macro stops and defines the following macros:
FUNCTION_TAG1, FUNCTION_TAG2, ... using AC_DEFINE() with values set to the
current values of <TAG1>, <TAG2>, ... If no combination is
successfull the configure script is aborted with a message.
</p>
<p>
Intended purpose is to find which combination of argument types is
acceptable for a given function <function>. It is recommended to list
the most specific types first. For instance ARG1, [size_t, int] instead of
ARG1, [int, size_t].
</p>
<p>
Generic usage pattern:
</p>
<p>
1) add a call in configure.in
</p>
<pre>
AC_PROTOTYPE(...)
</pre>
<p>
2) call autoheader to see which symbols are not covered
</p>
<p>
3) add the lines in acconfig.h
</p>
<pre>
/* Type of Nth argument of function */
#undef FUNCTION_ARGN
</pre>
<p>
4) Within the code use FUNCTION_ARGN instead of an hardwired type
</p>
<p>
Complete example:
</p>
<p>
1) configure.in
</p>
<pre>
AC_PROTOTYPE(getpeername,
[
#include <sys/types.h>
#include <sys/socket.h>
],
[
int a = 0;
ARG2 * b = 0;
ARG3 * c = 0;
getpeername(a, b, c);
],
ARG2, [struct sockaddr, void],
ARG3, [socklen_t, size_t, int, unsigned int, long unsigned int])
</pre>
<p>
2) call autoheader
</p>
<pre>
autoheader: Symbol `GETPEERNAME_ARG2' is not covered by ./acconfig.h
autoheader: Symbol `GETPEERNAME_ARG3' is not covered by ./acconfig.h
</pre>
<p>
3) acconfig.h
</p>
<pre>
/* Type of second argument of getpeername */
#undef GETPEERNAME_ARG2
/* Type of third argument of getpeername */
#undef GETPEERNAME_ARG3
</pre>
<p>
4) in the code
</p>
<pre>
...
GETPEERNAME_ARG2 name;
GETPEERNAME_ARG3 namelen;
...
ret = getpeername(socket, &name, &namelen);
...
</pre>
<p>
Implementation notes: generating all possible permutations of the arguments
is not easily done with the usual mixture of shell and m4, that is why this
macro is almost 100% m4 code. It generates long but simple to read code.
</p>
</div>
<h2>
SOURCE CODE
</h2>
<p class="indent">
<a href=
"http://autoconf-archive.cryp.to/ac_prototype.m4">http://autoconf-archive.cryp.to/ac_prototype.m4</a>
</p>
<h2>
LICENSE
</h2>
<div class="indent">
<p style="white-space:nowrap;">
Copyright © 2009 Loic Dachary <loic@senga.org>
</p>
<p>
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your option)
any later version.
</p>
<p>
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.
</p>
<p>
You should have received a copy of the GNU General Public License along
with this program. If not, see <<a href=
"http://www.gnu.org/licenses/">http://www.gnu.org/licenses/</a>>.
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