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68 lines
2.6 KiB
C
Executable File
68 lines
2.6 KiB
C
Executable File
/* xalloc-oversized.h -- memory allocation size checking
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Copyright (C) 1990-2000, 2003-2004, 2006-2023 Free Software Foundation, Inc.
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(NB: I modified the original GPL boilerplate here to LGPLv2+. This
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is because of the weird way that gnulib uses licenses, where the
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real license is covered in the modules/X file. The real license
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for this file is LGPLv2+, not GPL. - RWMJ)
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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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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#include <stdint.h>
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/* True if N * S would overflow in a size_t calculation,
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or would generate a value larger than PTRDIFF_MAX.
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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 size_t-based dividend to use here
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is SIZE_MAX - 1. */
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#define __xalloc_oversized(n, s) \
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((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))
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#if PTRDIFF_MAX < SIZE_MAX
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typedef ptrdiff_t __xalloc_count_type;
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#else
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typedef size_t __xalloc_count_type;
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#endif
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/* Return 1 if an array of N objects, each of size S, cannot exist
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reliably due to size or ptrdiff_t arithmetic overflow. S must be
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positive and N must be nonnegative. This is a macro, not a
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function, so that it works correctly even when SIZE_MAX < N. */
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#if 7 <= __GNUC__ && !defined __clang__
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# define xalloc_oversized(n, s) \
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__builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1)
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#elif 5 <= __GNUC__ && !defined __ICC && !__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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: ({ __xalloc_count_type __xalloc_count; \
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__builtin_mul_overflow (n, s, &__xalloc_count); }))
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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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