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Diffstat (limited to 'm4/size_max.m4')
-rw-r--r-- | m4/size_max.m4 | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/m4/size_max.m4 b/m4/size_max.m4 new file mode 100644 index 000000000..bfba811eb --- /dev/null +++ b/m4/size_max.m4 | |||
@@ -0,0 +1,62 @@ | |||
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 | ]) | ||