| # size_max.m4 serial 4 |
| dnl Copyright (C) 2003, 2005-2006 Free Software Foundation, Inc. |
| dnl This file is free software; the Free Software Foundation |
| dnl gives unlimited permission to copy and/or distribute it, |
| dnl with or without modifications, as long as this notice is preserved. |
| |
| dnl From Bruno Haible. |
| |
| AC_DEFUN([gl_SIZE_MAX], |
| [ |
| AC_CHECK_HEADERS(stdint.h) |
| dnl First test whether the system already has SIZE_MAX. |
| AC_MSG_CHECKING([for SIZE_MAX]) |
| result= |
| AC_EGREP_CPP([Found it], [ |
| #include <limits.h> |
| #if HAVE_STDINT_H |
| #include <stdint.h> |
| #endif |
| #ifdef SIZE_MAX |
| Found it |
| #endif |
| ], result=yes) |
| if test -z "$result"; then |
| dnl Define it ourselves. Here we assume that the type 'size_t' is not wider |
| dnl than the type 'unsigned long'. Try hard to find a definition that can |
| dnl be used in a preprocessor #if, i.e. doesn't contain a cast. |
| _AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1, |
| [#include <stddef.h> |
| #include <limits.h>], size_t_bits_minus_1=) |
| _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint, |
| [#include <stddef.h>], fits_in_uint=) |
| if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then |
| if test $fits_in_uint = 1; then |
| dnl Even though SIZE_MAX fits in an unsigned int, it must be of type |
| dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. |
| AC_TRY_COMPILE([#include <stddef.h> |
| extern size_t foo; |
| extern unsigned long foo; |
| ], [], fits_in_uint=0) |
| fi |
| dnl We cannot use 'expr' to simplify this expression, because 'expr' |
| dnl works only with 'long' integers in the host environment, while we |
| dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. |
| if test $fits_in_uint = 1; then |
| result="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" |
| else |
| result="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" |
| fi |
| else |
| dnl Shouldn't happen, but who knows... |
| result='((size_t)~(size_t)0)' |
| fi |
| fi |
| AC_MSG_RESULT([$result]) |
| if test "$result" != yes; then |
| AC_DEFINE_UNQUOTED([SIZE_MAX], [$result], |
| [Define as the maximum value of type 'size_t', if the system doesn't define it.]) |
| fi |
| ]) |
