1 # size_max.m4 serial 2 2 dnl Copyright (C) 2003 Free Software Foundation, Inc. 3 dnl This file is free software, distributed under the terms of the GNU 4 dnl General Public License. As a special exception to the GNU General 5 dnl Public License, this file may be distributed as part of a program 6 dnl that contains a configuration script generated by Autoconf, under 7 dnl the same distribution terms as the rest of that program. 8 9 dnl From Bruno Haible. 10 11 AC_DEFUN([gl_SIZE_MAX], 12 [ 13 AC_CHECK_HEADERS(stdint.h) 14 dnl First test whether the system already has SIZE_MAX. 15 AC_MSG_CHECKING([for SIZE_MAX]) 16 result= 17 AC_EGREP_CPP([Found it], [ 18 #include <limits.h> 19 #if HAVE_STDINT_H 20 #include <stdint.h> 21 #endif 22 #ifdef SIZE_MAX 23 Found it 24 #endif 25 ], result=yes) 26 if test -z "$result"; then 27 dnl Define it ourselves. Here we assume that the type 'size_t' is not wider 28 dnl than the type 'unsigned long'. 29 dnl The _AC_COMPUTE_INT macro works up to LONG_MAX, since it uses 'expr', 30 dnl which is guaranteed to work from LONG_MIN to LONG_MAX. 31 _AC_COMPUTE_INT([~(size_t)0 / 10], res_hi, 32 [#include <stddef.h>], result=?) 33 _AC_COMPUTE_INT([~(size_t)0 % 10], res_lo, 34 [#include <stddef.h>], result=?) 35 _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint, 36 [#include <stddef.h>], result=?) 37 if test "$fits_in_uint" = 1; then 38 dnl Even though SIZE_MAX fits in an unsigned int, it must be of type 39 dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. 40 AC_TRY_COMPILE([#include <stddef.h> 41 extern size_t foo; 42 extern unsigned long foo; 43 ], [], fits_in_uint=0) 44 fi 45 if test -z "$result"; then 46 if test "$fits_in_uint" = 1; then 47 result="$res_hi$res_lo"U 48 else 49 result="$res_hi$res_lo"UL 50 fi 51 else 52 dnl Shouldn't happen, but who knows... 53 result='~(size_t)0' 54 fi 55 fi 56 AC_MSG_RESULT([$result]) 57 if test "$result" != yes; then 58 AC_DEFINE_UNQUOTED([SIZE_MAX], [$result], 59 [Define as the maximum value of type 'size_t', if the system doesn't define it.]) 60 fi 61 ]) 62
