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Annotation of embedaddon/libiconv/srclib/xalloc-oversized.h, revision 1.1.1.1

1.1       misho       1: /* xalloc-oversized.h -- memory allocation size checking
                      2: 
                      3:    Copyright (C) 1990-2000, 2003-2004, 2006-2019 Free Software Foundation, Inc.
                      4: 
                      5:    This program is free software: you can redistribute it and/or modify
                      6:    it under the terms of the GNU General Public License as published by
                      7:    the Free Software Foundation; either version 3 of the License, or
                      8:    (at your option) any later version.
                      9: 
                     10:    This program is distributed in the hope that it will be useful,
                     11:    but WITHOUT ANY WARRANTY; without even the implied warranty of
                     12:    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
                     13:    GNU General Public License for more details.
                     14: 
                     15:    You should have received a copy of the GNU General Public License
                     16:    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
                     17: 
                     18: #ifndef XALLOC_OVERSIZED_H_
                     19: #define XALLOC_OVERSIZED_H_
                     20: 
                     21: #include <stddef.h>
                     22: #include <stdint.h>
                     23: 
                     24: /* True if N * S would overflow in a size_t calculation,
                     25:    or would generate a value larger than PTRDIFF_MAX.
                     26:    This expands to a constant expression if N and S are both constants.
                     27:    By gnulib convention, SIZE_MAX represents overflow in size
                     28:    calculations, so the conservative size_t-based dividend to use here
                     29:    is SIZE_MAX - 1.  */
                     30: #define __xalloc_oversized(n, s) \
                     31:   ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))
                     32: 
                     33: #if PTRDIFF_MAX < SIZE_MAX
                     34: typedef ptrdiff_t __xalloc_count_type;
                     35: #else
                     36: typedef size_t __xalloc_count_type;
                     37: #endif
                     38: 
                     39: /* Return 1 if an array of N objects, each of size S, cannot exist
                     40:    reliably due to size or ptrdiff_t arithmetic overflow.  S must be
                     41:    positive and N must be nonnegative.  This is a macro, not a
                     42:    function, so that it works correctly even when SIZE_MAX < N.  */
                     43: 
                     44: #if 7 <= __GNUC__
                     45: # define xalloc_oversized(n, s) \
                     46:    __builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1)
                     47: #elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__
                     48: # define xalloc_oversized(n, s) \
                     49:    (__builtin_constant_p (n) && __builtin_constant_p (s) \
                     50:     ? __xalloc_oversized (n, s) \
                     51:     : ({ __xalloc_count_type __xalloc_count; \
                     52:          __builtin_mul_overflow (n, s, &__xalloc_count); }))
                     53: 
                     54: /* Other compilers use integer division; this may be slower but is
                     55:    more portable.  */
                     56: #else
                     57: # define xalloc_oversized(n, s) __xalloc_oversized (n, s)
                     58: #endif
                     59: 
                     60: #endif /* !XALLOC_OVERSIZED_H_ */