1# size_max.m4 serial 2
2dnl Copyright (C) 2003 Free Software Foundation, Inc.
3dnl This file is free software, distributed under the terms of the GNU
4dnl General Public License.  As a special exception to the GNU General
5dnl Public License, this file may be distributed as part of a program
6dnl that contains a configuration script generated by Autoconf, under
7dnl the same distribution terms as the rest of that program.
8
9dnl From Bruno Haible.
10
11AC_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
23Found 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