/* xalloc-oversized.h -- memory allocation size checking

   Copyright (C) 1990-2000, 2003-2004, 2006-2020 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#ifndef XALLOC_OVERSIZED_H_

#define XALLOC_OVERSIZED_H_

#include <stddef.h>

#include <stdint.h>

/* True if N * S would overflow in a size_t calculation,

   or would generate a value larger than PTRDIFF_MAX.

   This expands to a constant expression if N and S are both constants.

   By gnulib convention, SIZE_MAX represents overflow in size

   calculations, so the conservative size_t-based dividend to use here

   is SIZE_MAX - 1.  */

#define __xalloc_oversized(n, s) \

  ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))

#if PTRDIFF_MAX < SIZE_MAX

typedef ptrdiff_t __xalloc_count_type;

#else

typedef size_t __xalloc_count_type;

#endif

/* Return 1 if an array of N objects, each of size S, cannot exist

   reliably due to size or ptrdiff_t arithmetic overflow.  S must be

   positive and N must be nonnegative.  This is a macro, not a

   function, so that it works correctly even when SIZE_MAX < N.  */

#if 7 <= __GNUC__

# define xalloc_oversized(n, s) \

   __builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1)

#elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__

# define xalloc_oversized(n, s) \

   (__builtin_constant_p (n) && __builtin_constant_p (s) \

    ? __xalloc_oversized (n, s) \

    : ({ __xalloc_count_type __xalloc_count; \

         __builtin_mul_overflow (n, s, &__xalloc_count); }))

/* Other compilers use integer division; this may be slower but is

   more portable.  */

#else

# define xalloc_oversized(n, s) __xalloc_oversized (n, s)

#endif

#endif /* !XALLOC_OVERSIZED_H_ */