1# size_max.m4 serial 9
2dnl Copyright (C) 2003, 2005-2006, 2008-2010 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_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [
14    gl_cv_size_max=
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], [gl_cv_size_max=yes])
24    if test -z "$gl_cv_size_max"; then
25      dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
26      dnl than the type 'unsigned long'. Try hard to find a definition that can
27      dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
28      AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1],
29        [#include <stddef.h>
30#include <limits.h>], [size_t_bits_minus_1=])
31      AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)],
32        [#include <stddef.h>], [fits_in_uint=])
33      if test -n "$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          gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
47        else
48          gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
49        fi
50      else
51        dnl Shouldn't happen, but who knows...
52        gl_cv_size_max='((size_t)~(size_t)0)'
53      fi
54    fi
55  ])
56  if test "$gl_cv_size_max" != yes; then
57    AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max],
58      [Define as the maximum value of type 'size_t', if the system doesn't define it.])
59  fi
60  dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after
61  dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with
62  dnl #define by AC_DEFINE_UNQUOTED.
63  AH_VERBATIM([SIZE_MAX],
64[/* Define as the maximum value of type 'size_t', if the system doesn't define
65   it. */
66#ifndef SIZE_MAX
67# undef SIZE_MAX
68#endif])
69])
70
71dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in.
72dnl Remove this when we can assume autoconf >= 2.61.
73m4_ifdef([AC_COMPUTE_INT], [], [
74  AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])])
75])
76