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Autoconf Macro: ac_sys_largefile_sensitive
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<h1>
ac_sys_largefile_sensitive
</h1>
<h2>
Synopsis
</h2>
<p class="indent" style="white-space:nowrap;">
<code>AC_SYS_LARGEFILE_SENSITIVE</code>
</p>
<h2>
Description
</h2>
<div class="indent">
<p>
checker whether the current system is sensitive to -Ddefines making off_t
having different types/sizes. Automatically define a config.h symbol
LARGEFILE_SENSITIVE if that is the case, otherwise leave everything as is.
</p>
<p>
This macro builds on top of AC_SYS_LARGEFILE to detect whether special
options are neede to make the code use 64bit off_t - in many setups this
will also make the code use 64bit off_t immediatly.
</p>
<p>
The common use of a LARGEFILE_SENSITIVE config.h-define is to rename
exported functions, usually adding a 64 to the original function name. Such
renamings are only needed on systems being both (a) 32bit off_t by default
and (b) implementing large.file extensions (as for unix98).
</p>
<p>
a renaming section could look like this:
</p>
<pre>
#if defined LARGEFILE_SENSITIVE && _FILE_OFFSET_BITS+0 == 64
#define zzip_open zzip_open64
#define zzip_seek zzip_seek64
#endif
</pre>
<p>
for libraries, it is best to take advantage of the prefix-config.h macro,
otherwise you want to export a renamed LARGEFILE_SENSITIVE in an installed
header file. -> see AX_PREFIX_CONFIG_H
</p>
</div>
<h2>
Author
</h2>
<p class="indent">
Guido Draheim <guidod@gmx.de>
</p>
<h2>
Last Modified
</h2>
<p class="indent">
2003-02-02
</p>
<h2>
M4 Source Code
</h2>
<div class="indent">
<pre class="m4source">
AC_DEFUN([AC_SYS_LARGEFILE_SENSITIVE],[dnl
AC_REQUIRE([AC_SYS_LARGEFILE])dnl
# we know about some internals of ac_sys_largefile here...
AC_MSG_CHECKING(whether system differentiates 64bit off_t by defines)
ac_cv_sys_largefile_sensitive="no"
if test ".$ac_cv_sys_file_offset_bits$ac_cv_sys_large_files" != ".nono"
then ac_cv_sys_largefile_sensitive="yes"
AC_DEFINE(LARGEFILE_SENSITIVE, 1,
[whether the system defaults to 32bit off_t but can do 64bit when requested])
fi
AC_MSG_RESULT([$ac_cv_sys_largefile_sensitive])
])
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