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61 lines
2.2 KiB
Plaintext
61 lines
2.2 KiB
Plaintext
# size_max.m4 serial 4
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dnl Copyright (C) 2003, 2005-2006 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_MSG_CHECKING([for SIZE_MAX])
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result=
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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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], result=yes)
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if test -z "$result"; then
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dnl Define it ourselves. Here we assume that the type 'size_t' is not wider
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dnl than the type 'unsigned long'. Try hard to find a definition that can
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dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
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_AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1,
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[#include <stddef.h>
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#include <limits.h>], size_t_bits_minus_1=)
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_AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint,
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[#include <stddef.h>], fits_in_uint=)
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if test -n "$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_TRY_COMPILE([#include <stddef.h>
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extern size_t foo;
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extern unsigned long foo;
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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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result="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)"
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else
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result="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)"
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fi
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else
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dnl Shouldn't happen, but who knows...
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result='((size_t)~(size_t)0)'
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fi
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fi
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AC_MSG_RESULT([$result])
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if test "$result" != yes; then
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AC_DEFINE_UNQUOTED([SIZE_MAX], [$result],
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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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])
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