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Autoconf Macro: ax_c_declare_block
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<h1>
ax_c_declare_block
</h1>
<h2>
Synopsis
</h2>
<p class="indent" style="white-space:nowrap;">
<code>AX_C_DECLARE_BLOCK</code>
</p>
<h2>
Description
</h2>
<div class="indent">
<p>
The macro will compile a test program to see whether the compiler does
allow new variable declarations in the middle of a C statement block, i.e.
after some non-declaration line. New compilers will allow that which makes
the behave a bit more like C++ - the gcc did support it for quite a time
already.
</p>
<p>
#define DECLARE_BLOCK_NEEDED says they need to be at the beginning of of a
statement block. Additionlly two defines DECLARE_BLOCK { and DECLARE_END }
are being set. That makes it possible to do the following in your source
code (which this macro is really made up for):
</p>
<pre>
#define ___ DECLARE_BLOCK
#define ____ DECLARE_END
int f() {
char buffer[1024];
fgets(buffer, 1024, stdin);
___ int i; int ii = strlen(buffer);
for (i=0; i < ii; i++) {
fputc(buffer[i], stdout);
}____;
}
</pre>
</div>
<h2>
Author
</h2>
<p class="indent">
Guido U. Draheim <guidod@gmx.de>
</p>
<h2>
Last Modified
</h2>
<p class="indent">
2006-08-10
</p>
<h2>
M4 Source Code
</h2>
<div class="indent">
<pre class="m4source">
AC_DEFUN([AX_C_DECLARE_BLOCK],[dnl
AC_CACHE_CHECK(
[if C variables must be declared at the beginning of a block],
ax_cv_c_declare_block,[
AC_TRY_COMPILE([#include <stdio.h>
int f() {
char buffer[1024];
fgets(buffer, 1024, stdin);
int i; int ii = strlen(buffer);
for (i=0; i < ii; i++) {
fputc(buffer[i], stdout);
}
}],
[],
ax_cv_c_declare_block=no, ax_cv_c_declare_block=yes)])
if test "$ax_cv_c_declare_block" = yes; then
AC_DEFINE([DECLARE_BLOCK_NEEDED],[1],
[if C variables must be declared at the beginning of a block])
AC_DEFINE([DECLARE_BLOCK],[{],
[set to { if variable declarations need a block start before])
AC_DEFINE([DECLARE_END],[}],
[set to } if variable declarations need a block start before])
fi
])
</pre>
</div>
<h2>
License
</h2>
<div class="indent">
<span style="white-space:nowrap;">Copyright © 2006 Guido U. Draheim
<guidod@gmx.de></span>
<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, write to the Free Software Foundation, Inc., 59
Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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