Annotation of embedaddon/confuse/m4/size_max.m4, revision 1.1.1.1
1.1 misho 1: # size_max.m4 serial 5
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: AC_CACHE_VAL([gl_cv_size_max], [
15: gl_cv_size_max=
16: AC_EGREP_CPP([Found it], [
17: #include <limits.h>
18: #if HAVE_STDINT_H
19: #include <stdint.h>
20: #endif
21: #ifdef SIZE_MAX
22: Found it
23: #endif
24: ], gl_cv_size_max=yes)
25: if test -z "$gl_cv_size_max"; then
26: dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
27: dnl than the type 'unsigned long'. Try hard to find a definition that can
28: dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
29: _AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1,
30: [#include <stddef.h>
31: #include <limits.h>], size_t_bits_minus_1=)
32: _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint,
33: [#include <stddef.h>], fits_in_uint=)
34: if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then
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: dnl We cannot use 'expr' to simplify this expression, because 'expr'
44: dnl works only with 'long' integers in the host environment, while we
45: dnl might be cross-compiling from a 32-bit platform to a 64-bit platform.
46: if test $fits_in_uint = 1; then
47: gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
48: else
49: gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
50: fi
51: else
52: dnl Shouldn't happen, but who knows...
53: gl_cv_size_max='((size_t)~(size_t)0)'
54: fi
55: fi
56: ])
57: AC_MSG_RESULT([$gl_cv_size_max])
58: if test "$gl_cv_size_max" != yes; then
59: AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max],
60: [Define as the maximum value of type 'size_t', if the system doesn't define it.])
61: fi
62: ])
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