| 1 | # size_max.m4 serial 2
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| 2 | dnl Copyright (C) 2003 Free Software Foundation, Inc.
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| 3 | dnl This file is free software, distributed under the terms of the GNU
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| 4 | dnl General Public License. As a special exception to the GNU General
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| 5 | dnl Public License, this file may be distributed as part of a program
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| 6 | dnl that contains a configuration script generated by Autoconf, under
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| 7 | dnl the same distribution terms as the rest of that program.
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| 8 |
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| 9 | dnl From Bruno Haible.
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| 10 |
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| 11 | AC_DEFUN([gl_SIZE_MAX],
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| 12 | [
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| 13 | AC_CHECK_HEADERS(stdint.h)
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| 14 | dnl First test whether the system already has SIZE_MAX.
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| 15 | AC_MSG_CHECKING([for SIZE_MAX])
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| 16 | result=
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| 17 | AC_EGREP_CPP([Found it], [
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| 18 | #include <limits.h>
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| 19 | #if HAVE_STDINT_H
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| 20 | #include <stdint.h>
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| 21 | #endif
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| 22 | #ifdef SIZE_MAX
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| 23 | Found it
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| 24 | #endif
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| 25 | ], result=yes)
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| 26 | if test -z "$result"; then
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| 27 | dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
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| 28 | dnl than the type 'unsigned long'.
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| 29 | dnl The _AC_COMPUTE_INT macro works up to LONG_MAX, since it uses 'expr',
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| 30 | dnl which is guaranteed to work from LONG_MIN to LONG_MAX.
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| 31 | _AC_COMPUTE_INT([~(size_t)0 / 10], res_hi,
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| 32 | [#include <stddef.h>], result=?)
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| 33 | _AC_COMPUTE_INT([~(size_t)0 % 10], res_lo,
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| 34 | [#include <stddef.h>], result=?)
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| 35 | _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint,
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| 36 | [#include <stddef.h>], result=?)
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| 37 | if test "$fits_in_uint" = 1; then
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| 38 | dnl Even though SIZE_MAX fits in an unsigned int, it must be of type
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| 39 | dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'.
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| 40 | AC_TRY_COMPILE([#include <stddef.h>
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| 41 | extern size_t foo;
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| 42 | extern unsigned long foo;
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| 43 | ], [], fits_in_uint=0)
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| 44 | fi
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| 45 | if test -z "$result"; then
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| 46 | if test "$fits_in_uint" = 1; then
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| 47 | result="$res_hi$res_lo"U
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| 48 | else
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| 49 | result="$res_hi$res_lo"UL
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| 50 | fi
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| 51 | else
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| 52 | dnl Shouldn't happen, but who knows...
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| 53 | result='~(size_t)0'
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| 54 | fi
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| 55 | fi
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| 56 | AC_MSG_RESULT([$result])
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| 57 | if test "$result" != yes; then
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| 58 | AC_DEFINE_UNQUOTED([SIZE_MAX], [$result],
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| 59 | [Define as the maximum value of type 'size_t', if the system doesn't define it.])
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| 60 | fi
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| 61 | ])
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