diff options
Diffstat (limited to 'm4')
| -rw-r--r-- | m4/size_max.m4 | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/m4/size_max.m4 b/m4/size_max.m4 new file mode 100644 index 000000000..6cb486892 --- /dev/null +++ b/m4/size_max.m4 @@ -0,0 +1,68 @@ +# size_max.m4 serial 6 +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 "$gl_cv_size_max"; then + dnl Define it ourselves. Here we assume that the type 'size_t' is not wider + dnl than the type 'unsigned long'. Try hard to find a definition that can + dnl be used in a preprocessor #if, i.e. doesn't contain a cast. + AC_COMPUTE_INT([size_t_bits_minus_1], [sizeof (size_t) * CHAR_BIT - 1], + [#include <stddef.h> +#include <limits.h>], size_t_bits_minus_1=) + AC_COMPUTE_INT([fits_in_uint], [sizeof (size_t) <= sizeof (unsigned int)], + [#include <stddef.h>], fits_in_uint=) + if test -n "$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 << $size_t_bits_minus_1) - 1) * 2 + 1)" + fi + else + dnl Shouldn't happen, but who knows... + gl_cv_size_max='((size_t)~(size_t)0)' + fi + fi + ]) + AC_MSG_RESULT([$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 +]) + +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])]) +]) |