1 # size_max.m4 serial 4 2 dnl Copyright (C) 2003, 2005-2006 Free Software Foundation, Inc. 3 dnl This file is free software; the Free Software Foundation 4 dnl gives unlimited permission to copy and/or distribute it, 5 dnl with or without modifications, as long as this notice is preserved. 6 7 dnl From Bruno Haible. 8 9 AC_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 21 Found it 22 #endif 23 ], result=yes) 24 if test -z "$result"; then 25 dnl Define it ourselves. Here we assume that the type 'size_t' is not wider 26 dnl than the type 'unsigned long'. Try hard to find a definition that can 27 dnl be used in a preprocessor #if, i.e. doesn't contain a cast. 28 _AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1, 29 [#include <stddef.h> 30 #include <limits.h>], size_t_bits_minus_1=) 31 _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint, 32 [#include <stddef.h>], fits_in_uint=) 33 if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then 34 if test $fits_in_uint = 1; then 35 dnl Even though SIZE_MAX fits in an unsigned int, it must be of type 36 dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. 37 AC_TRY_COMPILE([#include <stddef.h> 38 extern size_t foo; 39 extern unsigned long foo; 40 ], [], fits_in_uint=0) 41 fi 42 dnl We cannot use 'expr' to simplify this expression, because 'expr' 43 dnl works only with 'long' integers in the host environment, while we 44 dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. 45 if test $fits_in_uint = 1; then 46 result="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" 47 else 48 result="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" 49 fi 50 else 51 dnl Shouldn't happen, but who knows... 52 result='((size_t)~(size_t)0)' 53 fi 54 fi 55 AC_MSG_RESULT([$result]) 56 if test "$result" != yes; then 57 AC_DEFINE_UNQUOTED([SIZE_MAX], [$result], 58 [Define as the maximum value of type 'size_t', if the system doesn't define it.]) 59 fi 60 ]) 61
