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This incorporates: 2016-06-24 intprops: port better to GCC 7 2016-06-13 xalloc-oversized: port to GCC 7; fewer warnings * doc/misc/texinfo.tex, lib/xalloc-oversized.h, lib/intprops.h: Copy from gnulib.
71 lines
2.9 KiB
C
71 lines
2.9 KiB
C
/* xalloc-oversized.h -- memory allocation size checking
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Copyright (C) 1990-2000, 2003-2004, 2006-2016 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef XALLOC_OVERSIZED_H_
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#define XALLOC_OVERSIZED_H_
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#include <stddef.h>
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/* Default for (non-Clang) compilers that lack __has_builtin. */
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#ifndef __has_builtin
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# define __has_builtin(x) 0
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#endif
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/* True if N * S would overflow in a size calculation.
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This expands to a constant expression if N and S are both constants.
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By gnulib convention, SIZE_MAX represents overflow in size
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calculations, so the conservative dividend to use here is
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SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
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However, malloc (SIZE_MAX) fails on all known hosts where
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sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
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exactly-SIZE_MAX allocations on such hosts; this avoids a test and
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branch when S is known to be 1. */
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#define __xalloc_oversized(n, s) \
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((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
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/* Return 1 if an array of N objects, each of size S, cannot exist due
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to size arithmetic overflow. S must be positive and N must be
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nonnegative. This is a macro, not a function, so that it
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works correctly even when SIZE_MAX < N. */
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/* GCC 7 __builtin_mul_overflow should easily compute this. See:
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68120 */
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#if 7 <= __GNUC__
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# define xalloc_oversized(n, s) __builtin_mul_overflow (n, s, (size_t *) NULL)
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/* GCC 5 and Clang __builtin_mul_overflow needs a temporary, and
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should be used only for non-constant operands, so that
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xalloc_oversized is a constant expression if both arguments are.
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Do not use this if pedantic, since pedantic GCC issues a diagnostic
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for ({ ... }). */
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#elif ((5 <= __GNUC__ \
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|| (__has_builtin (__builtin_mul_overflow) \
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&& __has_builtin (__builtin_constant_p))) \
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&& !__STRICT_ANSI__)
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# define xalloc_oversized(n, s) \
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(__builtin_constant_p (n) && __builtin_constant_p (s) \
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? __xalloc_oversized (n, s) \
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: ({ size_t __xalloc_size; __builtin_mul_overflow (n, s, &__xalloc_size); }))
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/* Other compilers use integer division; this may be slower but is
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more portable. */
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#else
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# define xalloc_oversized(n, s) __xalloc_oversized (n, s)
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#endif
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#endif /* !XALLOC_OVERSIZED_H_ */
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