1# ============================================================================ 2# https://www.gnu.org/software/autoconf-archive/ax_compile_check_sizeof.html 3# ============================================================================ 4# 5# SYNOPSIS 6# 7# AX_COMPILE_CHECK_SIZEOF(TYPE [, HEADERS [, EXTRA_SIZES...]]) 8# 9# DESCRIPTION 10# 11# This macro checks for the size of TYPE using compile checks, not run 12# checks. You can supply extra HEADERS to look into. the check will cycle 13# through 1 2 4 8 16 and any EXTRA_SIZES the user supplies. If a match is 14# found, it will #define SIZEOF_`TYPE' to that value. Otherwise it will 15# emit a configure time error indicating the size of the type could not be 16# determined. 17# 18# The trick is that C will not allow duplicate case labels. While this is 19# valid C code: 20# 21# switch (0) case 0: case 1:; 22# 23# The following is not: 24# 25# switch (0) case 0: case 0:; 26# 27# Thus, the AC_TRY_COMPILE will fail if the currently tried size does not 28# match. 29# 30# Here is an example skeleton configure.in script, demonstrating the 31# macro's usage: 32# 33# AC_PROG_CC 34# AC_CHECK_HEADERS(stddef.h unistd.h) 35# AC_TYPE_SIZE_T 36# AC_CHECK_TYPE(ssize_t, int) 37# 38# headers='#ifdef HAVE_STDDEF_H 39# #include <stddef.h> 40# #endif 41# #ifdef HAVE_UNISTD_H 42# #include <unistd.h> 43# #endif 44# ' 45# 46# AX_COMPILE_CHECK_SIZEOF(char) 47# AX_COMPILE_CHECK_SIZEOF(short) 48# AX_COMPILE_CHECK_SIZEOF(int) 49# AX_COMPILE_CHECK_SIZEOF(long) 50# AX_COMPILE_CHECK_SIZEOF(unsigned char *) 51# AX_COMPILE_CHECK_SIZEOF(void *) 52# AX_COMPILE_CHECK_SIZEOF(size_t, $headers) 53# AX_COMPILE_CHECK_SIZEOF(ssize_t, $headers) 54# AX_COMPILE_CHECK_SIZEOF(ptrdiff_t, $headers) 55# AX_COMPILE_CHECK_SIZEOF(off_t, $headers) 56# 57# LICENSE 58# 59# Copyright (c) 2008 Kaveh Ghazi <ghazi@caip.rutgers.edu> 60# Copyright (c) 2017 Reini Urban <rurban@cpan.org> 61# 62# This program is free software: you can redistribute it and/or modify it 63# under the terms of the GNU General Public License as published by the 64# Free Software Foundation, either version 3 of the License, or (at your 65# option) any later version. 66# 67# This program is distributed in the hope that it will be useful, but 68# WITHOUT ANY WARRANTY; without even the implied warranty of 69# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General 70# Public License for more details. 71# 72# You should have received a copy of the GNU General Public License along 73# with this program. If not, see <https://www.gnu.org/licenses/>. 74# 75# As a special exception, the respective Autoconf Macro's copyright owner 76# gives unlimited permission to copy, distribute and modify the configure 77# scripts that are the output of Autoconf when processing the Macro. You 78# need not follow the terms of the GNU General Public License when using 79# or distributing such scripts, even though portions of the text of the 80# Macro appear in them. The GNU General Public License (GPL) does govern 81# all other use of the material that constitutes the Autoconf Macro. 82# 83# This special exception to the GPL applies to versions of the Autoconf 84# Macro released by the Autoconf Archive. When you make and distribute a 85# modified version of the Autoconf Macro, you may extend this special 86# exception to the GPL to apply to your modified version as well. 87 88#serial 7 89 90AU_ALIAS([AC_COMPILE_CHECK_SIZEOF], [AX_COMPILE_CHECK_SIZEOF]) 91AC_DEFUN([AX_COMPILE_CHECK_SIZEOF], 92[changequote(<<, >>)dnl 93dnl The name to #define. 94define(<<AC_TYPE_NAME>>, translit(sizeof_$1, [a-z *], [A-Z_P]))dnl 95dnl The cache variable name. 96define(<<AC_CV_NAME>>, translit(ac_cv_sizeof_$1, [ *], [_p]))dnl 97changequote([, ])dnl 98AC_MSG_CHECKING(size of $1) 99AC_CACHE_VAL(AC_CV_NAME, 100[for ac_size in 4 8 1 2 16 $3 ; do # List sizes in rough order of prevalence. 101 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ 102#include <sys/types.h> 103$2 104]], [[switch (0) case 0: case (sizeof ($1) == $ac_size):;]])], [AC_CV_NAME=$ac_size]) 105 if test x$AC_CV_NAME != x ; then break; fi 106done 107]) 108if test x$AC_CV_NAME = x ; then 109 AC_MSG_ERROR([cannot determine a size for $1]) 110fi 111AC_MSG_RESULT($AC_CV_NAME) 112AC_DEFINE_UNQUOTED(AC_TYPE_NAME, $AC_CV_NAME, [The number of bytes in type $1]) 113undefine([AC_TYPE_NAME])dnl 114undefine([AC_CV_NAME])dnl 115]) 116