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79 lines
3.0 KiB
79 lines
3.0 KiB
# size_max.m4 serial 10 |
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dnl Copyright (C) 2003, 2005-2006, 2008-2017 Free Software Foundation, Inc. |
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dnl This file is free software; the Free Software Foundation |
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dnl gives unlimited permission to copy and/or distribute it, |
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dnl with or without modifications, as long as this notice is preserved. |
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dnl From Bruno Haible. |
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AC_DEFUN([gl_SIZE_MAX], |
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[ |
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AC_CHECK_HEADERS([stdint.h]) |
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dnl First test whether the system already has SIZE_MAX. |
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AC_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [ |
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gl_cv_size_max= |
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AC_EGREP_CPP([Found it], [ |
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#include <limits.h> |
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#if HAVE_STDINT_H |
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#include <stdint.h> |
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#endif |
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#ifdef SIZE_MAX |
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Found it |
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#endif |
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], [gl_cv_size_max=yes]) |
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if test -z "$gl_cv_size_max"; then |
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dnl Define it ourselves. Here we assume that the type 'size_t' is not wider |
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dnl than the type 'unsigned long'. Try hard to find a definition that can |
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dnl be used in a preprocessor #if, i.e. doesn't contain a cast. |
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AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1], |
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[#include <stddef.h> |
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#include <limits.h>], [size_t_bits_minus_1=]) |
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AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)], |
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[#include <stddef.h>], [fits_in_uint=]) |
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if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then |
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if test $fits_in_uint = 1; then |
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dnl Even though SIZE_MAX fits in an unsigned int, it must be of type |
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dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. |
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AC_COMPILE_IFELSE( |
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[AC_LANG_PROGRAM( |
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[[#include <stddef.h> |
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extern size_t foo; |
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extern unsigned long foo; |
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]], |
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[[]])], |
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[fits_in_uint=0]) |
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fi |
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dnl We cannot use 'expr' to simplify this expression, because 'expr' |
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dnl works only with 'long' integers in the host environment, while we |
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dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. |
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if test $fits_in_uint = 1; then |
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gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" |
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else |
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gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" |
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fi |
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else |
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dnl Shouldn't happen, but who knows... |
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gl_cv_size_max='((size_t)~(size_t)0)' |
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fi |
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fi |
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]) |
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if test "$gl_cv_size_max" != yes; then |
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AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max], |
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[Define as the maximum value of type 'size_t', if the system doesn't define it.]) |
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fi |
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dnl Don't redefine SIZE_MAX in config.h if config.h is re-included after |
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dnl <stdint.h>. Remember that the #undef in AH_VERBATIM gets replaced with |
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dnl #define by AC_DEFINE_UNQUOTED. |
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AH_VERBATIM([SIZE_MAX], |
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[/* Define as the maximum value of type 'size_t', if the system doesn't define |
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it. */ |
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#ifndef SIZE_MAX |
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# undef SIZE_MAX |
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#endif]) |
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]) |
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dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in. |
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dnl Remove this when we can assume autoconf >= 2.61. |
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m4_ifdef([AC_COMPUTE_INT], [], [ |
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AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])]) |
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])
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