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Diffstat (limited to '')
| -rw-r--r-- | m4/size_max.m4 | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/m4/size_max.m4 b/m4/size_max.m4 new file mode 100644 index 0000000..ab79052 --- /dev/null +++ b/m4/size_max.m4 @@ -0,0 +1,75 @@ +# size_max.m4 serial 11 +dnl Copyright (C) 2003, 2005-2006, 2008-2019 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_PREREQ([2.61]) + +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_COMPILE_IFELSE( + [AC_LANG_PROGRAM( + [[#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]) +]) |