1# size_max.m4 serial 2 2dnl Copyright (C) 2003 Free Software Foundation, Inc. 3dnl This file is free software; the Free Software Foundation 4dnl gives unlimited permission to copy and/or distribute it, 5dnl with or without modifications, as long as this notice is preserved. 6 7dnl From Bruno Haible. 8 9AC_DEFUN([gl_SIZE_MAX], 10[ 11 AC_CHECK_HEADERS(stdint.h) 12 dnl First test whether the system already has SIZE_MAX. 13 AC_MSG_CHECKING([for SIZE_MAX]) 14 result= 15 AC_EGREP_CPP([Found it], [ 16#include <limits.h> 17#if HAVE_STDINT_H 18#include <stdint.h> 19#endif 20#ifdef SIZE_MAX 21Found it 22#endif 23], result=yes) 24 if test -z "$result"; then 25 dnl Define it ourselves. Here we assume that the type 'size_t' is not wider 26 dnl than the type 'unsigned long'. 27 dnl The _AC_COMPUTE_INT macro works up to LONG_MAX, since it uses 'expr', 28 dnl which is guaranteed to work from LONG_MIN to LONG_MAX. 29 _AC_COMPUTE_INT([~(size_t)0 / 10], res_hi, 30 [#include <stddef.h>], result=?) 31 _AC_COMPUTE_INT([~(size_t)0 % 10], res_lo, 32 [#include <stddef.h>], result=?) 33 _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint, 34 [#include <stddef.h>], result=?) 35 if test "$fits_in_uint" = 1; then 36 dnl Even though SIZE_MAX fits in an unsigned int, it must be of type 37 dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. 38 AC_TRY_COMPILE([#include <stddef.h> 39 extern size_t foo; 40 extern unsigned long foo; 41 ], [], fits_in_uint=0) 42 fi 43 if test -z "$result"; then 44 if test "$fits_in_uint" = 1; then 45 result="$res_hi$res_lo"U 46 else 47 result="$res_hi$res_lo"UL 48 fi 49 else 50 dnl Shouldn't happen, but who knows... 51 result='~(size_t)0' 52 fi 53 fi 54 AC_MSG_RESULT([$result]) 55 if test "$result" != yes; then 56 AC_DEFINE_UNQUOTED([SIZE_MAX], [$result], 57 [Define as the maximum value of type 'size_t', if the system doesn't define it.]) 58 fi 59]) 60