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authorNils Durner <durner@gnunet.org>2009-05-29 19:20:23 +0000
committerNils Durner <durner@gnunet.org>2009-05-29 19:20:23 +0000
commit179946965cc0f171e4af1bd053b42ec36314c86e (patch)
treedf49518ea91d8a644ecbd0e6a48c26c1e7fe93b3 /m4/size_max.m4
parentc137702c332798fb68622739f61ae06bbf6286df (diff)
cp
Diffstat (limited to 'm4/size_max.m4')
-rw-r--r--m4/size_max.m462
1 files changed, 62 insertions, 0 deletions
diff --git a/m4/size_max.m4 b/m4/size_max.m4
new file mode 100644
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+++ b/m4/size_max.m4
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+# size_max.m4 serial 5
+dnl Copyright (C) 2003, 2005-2006 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Bruno Haible.
+
+AC_DEFUN([gl_SIZE_MAX],
+[
+ AC_CHECK_HEADERS(stdint.h)
+ dnl First test whether the system already has SIZE_MAX.
+ AC_MSG_CHECKING([for SIZE_MAX])
+ AC_CACHE_VAL([gl_cv_size_max], [
+ gl_cv_size_max=
+ AC_EGREP_CPP([Found it], [
+#include <limits.h>
+#if HAVE_STDINT_H
+#include <stdint.h>
+#endif
+#ifdef SIZE_MAX
+Found it
+#endif
+], gl_cv_size_max=yes)
+ if test -z "$gl_cv_size_max"; then
+ dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
+ dnl than the type 'unsigned long'. Try hard to find a definition that can
+ dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
+ _AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1,
+ [#include <stddef.h>
+#include <limits.h>], size_t_bits_minus_1=)
+ _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint,
+ [#include <stddef.h>], fits_in_uint=)
+ if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then
+ if test $fits_in_uint = 1; then
+ dnl Even though SIZE_MAX fits in an unsigned int, it must be of type
+ dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'.
+ AC_TRY_COMPILE([#include <stddef.h>
+ extern size_t foo;
+ extern unsigned long foo;
+ ], [], fits_in_uint=0)
+ fi
+ dnl We cannot use 'expr' to simplify this expression, because 'expr'
+ dnl works only with 'long' integers in the host environment, while we
+ dnl might be cross-compiling from a 32-bit platform to a 64-bit platform.
+ if test $fits_in_uint = 1; then
+ gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
+ else
+ gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
+ fi
+ else
+ dnl Shouldn't happen, but who knows...
+ gl_cv_size_max='((size_t)~(size_t)0)'
+ fi
+ fi
+ ])
+ AC_MSG_RESULT([$gl_cv_size_max])
+ if test "$gl_cv_size_max" != yes; then
+ AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max],
+ [Define as the maximum value of type 'size_t', if the system doesn't define it.])
+ fi
+])