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size_max.m4
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# size_max.m4 serial 9 dnl Copyright (C) 2003, 2005-2006, 2008-2010 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_CACHE_CHECK([for SIZE_MAX], [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 "$gl_cv_size_max"; then dnl Define it ourselves. Here we assume that the type 'size_t' is not wider dnl than the type 'unsigned long'. Try hard to find a definition that can dnl be used in a preprocessor #if, i.e. doesn't contain a cast. AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1], [#include <stddef.h> #include <limits.h>], [size_t_bits_minus_1=]) AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)], [#include <stddef.h>], [fits_in_uint=]) if test -n "$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 << $size_t_bits_minus_1) - 1) * 2 + 1)" fi else dnl Shouldn't happen, but who knows... gl_cv_size_max='((size_t)~(size_t)0)' fi fi ]) if test "$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 dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with dnl #define by AC_DEFINE_UNQUOTED. AH_VERBATIM([SIZE_MAX], [/* Define as the maximum value of type 'size_t', if the system doesn't define it. */ #ifndef SIZE_MAX # undef SIZE_MAX #endif]) ]) dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in. dnl Remove this when we can assume autoconf >= 2.61. m4_ifdef([AC_COMPUTE_INT], [], [ AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])]) ])