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c4b681fd LC |
1 | # size_max.m4 serial 9 |
2 | dnl Copyright (C) 2003, 2005-2006, 2008-2009 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_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 | |
21 | Found 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 | ||
71 | dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in. | |
72 | dnl Remove this when we can assume autoconf >= 2.61. | |
73 | m4_ifdef([AC_COMPUTE_INT], [], [ | |
74 | AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])]) | |
75 | ]) |