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ax_compile_check_sizeof.m4
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# ============================================================================
# https://www.gnu.org/software/autoconf-archive/ax_compile_check_sizeof.html
# ============================================================================
#
# SYNOPSIS
#
# AX_COMPILE_CHECK_SIZEOF(TYPE [, HEADERS [, EXTRA_SIZES...]])
#
# DESCRIPTION
#
# This macro checks for the size of TYPE using compile checks, not run
# checks. You can supply extra HEADERS to look into. the check will cycle
# through 1 2 4 8 16 and any EXTRA_SIZES the user supplies. If a match is
# found, it will #define SIZEOF_`TYPE' to that value. Otherwise it will
# emit a configure time error indicating the size of the type could not be
# determined.
#
# The trick is that C will not allow duplicate case labels. While this is
# valid C code:
#
# switch (0) case 0: case 1:;
#
# The following is not:
#
# switch (0) case 0: case 0:;
#
# Thus, the AC_COMPILE_IFELSE will fail if the currently tried size does
# not match.
#
# Here is an example skeleton configure.in script, demonstrating the
# macro's usage:
#
# AC_PROG_CC
# AC_CHECK_HEADERS(stddef.h unistd.h)
# AC_TYPE_SIZE_T
# AC_CHECK_TYPE(ssize_t, int)
#
# headers='#ifdef HAVE_STDDEF_H
# #include <stddef.h>
# #endif
# #ifdef HAVE_UNISTD_H
# #include <unistd.h>
# #endif
# '
#
# AX_COMPILE_CHECK_SIZEOF(char)
# AX_COMPILE_CHECK_SIZEOF(short)
# AX_COMPILE_CHECK_SIZEOF(int)
# AX_COMPILE_CHECK_SIZEOF(long)
# AX_COMPILE_CHECK_SIZEOF(unsigned char *)
# AX_COMPILE_CHECK_SIZEOF(void *)
# AX_COMPILE_CHECK_SIZEOF(size_t, $headers)
# AX_COMPILE_CHECK_SIZEOF(ssize_t, $headers)
# AX_COMPILE_CHECK_SIZEOF(ptrdiff_t, $headers)
# AX_COMPILE_CHECK_SIZEOF(off_t, $headers)
#
# LICENSE
#
# Copyright (c) 2008 Kaveh Ghazi <[email protected]>
# Copyright (c) 2017 Reini Urban <[email protected]>
#
# 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 3 of the License, or (at your
# option) any later version.
#
# 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.
#
# You should have received a copy of the GNU General Public License along
# with this program. If not, see <https://www.gnu.org/licenses/>.
#
# As a special exception, the respective Autoconf Macro's copyright owner
# gives unlimited permission to copy, distribute and modify the configure
# scripts that are the output of Autoconf when processing the Macro. You
# need not follow the terms of the GNU General Public License when using
# or distributing such scripts, even though portions of the text of the
# Macro appear in them. The GNU General Public License (GPL) does govern
# all other use of the material that constitutes the Autoconf Macro.
#
# This special exception to the GPL applies to versions of the Autoconf
# Macro released by the Autoconf Archive. When you make and distribute a
# modified version of the Autoconf Macro, you may extend this special
# exception to the GPL to apply to your modified version as well.
#serial 8
AU_ALIAS([AC_COMPILE_CHECK_SIZEOF], [AX_COMPILE_CHECK_SIZEOF])
AC_DEFUN([AX_COMPILE_CHECK_SIZEOF],
[changequote(<<, >>)dnl
dnl The name to #define.
define(<<AC_TYPE_NAME>>, translit(sizeof_$1, [a-z *], [A-Z_P]))dnl
dnl The cache variable name.
define(<<AC_CV_NAME>>, translit(ac_cv_sizeof_$1, [ *], [_p]))dnl
changequote([, ])dnl
AC_MSG_CHECKING(size of $1)
AC_CACHE_VAL(AC_CV_NAME,
[for ac_size in 4 8 1 2 16 $3 ; do # List sizes in rough order of prevalence.
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
#include <sys/types.h>
$2
]], [[switch (0) case 0: case (sizeof ($1) == $ac_size):;]])], [AC_CV_NAME=$ac_size])
if test x$AC_CV_NAME != x ; then break; fi
done
])
if test x$AC_CV_NAME = x ; then
AC_MSG_ERROR([cannot determine a size for $1])
fi
AC_MSG_RESULT($AC_CV_NAME)
AC_DEFINE_UNQUOTED(AC_TYPE_NAME, $AC_CV_NAME, [The number of bytes in type $1])
undefine([AC_TYPE_NAME])dnl
undefine([AC_CV_NAME])dnl
])