diff options
Diffstat (limited to 'lib/xalloc-oversized.h')
| -rw-r--r-- | lib/xalloc-oversized.h | 64 |
1 files changed, 30 insertions, 34 deletions
diff --git a/lib/xalloc-oversized.h b/lib/xalloc-oversized.h index 30d12fd3..aefa6fd8 100644 --- a/lib/xalloc-oversized.h +++ b/lib/xalloc-oversized.h @@ -1,27 +1,18 @@ /* xalloc-oversized.h -- memory allocation size checking - Copyright (C) 1990-2000, 2003-2004, 2006-2018 Free Software Foundation, Inc. + Copyright (C) 1990-2000, 2003-2004, 2006-2022 Free Software Foundation, Inc. - This program is free software: you can redistribute it and/or - modify it under the terms of either: + This file is free software: you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License as + published by the Free Software Foundation; either version 2.1 of the + License, or (at your option) any later version. - * the GNU Lesser General Public License as published by the Free - Software Foundation; either version 3 of the License, or (at your - option) any later version. - - or - - * the GNU General Public License as published by the Free - Software Foundation; either version 2 of the License, or (at your - option) any later version. - - or both in parallel, as here. - This program is distributed in the hope that it will be useful, + This file 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. + GNU Lesser General Public License for more details. - You should have received a copy of the GNU General Public License + You should have received a copy of the GNU Lesser General Public License along with this program. If not, see <https://www.gnu.org/licenses/>. */ #ifndef XALLOC_OVERSIZED_H_ @@ -30,34 +21,39 @@ #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. +/* True if N * S does not fit into both ptrdiff_t and size_t. + N and S should be nonnegative and free of side effects. This expands to a constant expression if N and S are both constants. - By gnulib convention, SIZE_MAX represents overflow in size + By gnulib convention, SIZE_MAX represents overflow in size_t 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)) + ((s) != 0 \ + && ((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 and only if an array of N objects, each of size S, + cannot exist reliably because its total size in bytes would exceed + MIN (PTRDIFF_MAX, SIZE_MAX - 1). + + N and S should be nonnegative and free of side effects. -/* 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. */ + Warning: (xalloc_oversized (N, S) ? NULL : malloc (N * S)) can + misbehave if N and S are both narrower than ptrdiff_t and size_t, + and can be rewritten as (xalloc_oversized (N, S) ? NULL + : malloc (N * (size_t) S)). -#if 7 <= __GNUC__ + This is a macro, not a function, so that it works even if an + argument exceeds MAX (PTRDIFF_MAX, SIZE_MAX). */ +#if 7 <= __GNUC__ && !defined __clang__ && PTRDIFF_MAX < SIZE_MAX # define xalloc_oversized(n, s) \ - __builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1) -#elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__ + __builtin_mul_overflow_p (n, s, (ptrdiff_t) 1) +#elif (5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__ \ + && PTRDIFF_MAX < SIZE_MAX) # define xalloc_oversized(n, s) \ (__builtin_constant_p (n) && __builtin_constant_p (s) \ ? __xalloc_oversized (n, s) \ - : ({ __xalloc_count_type __xalloc_count; \ + : ({ ptrdiff_t __xalloc_count; \ __builtin_mul_overflow (n, s, &__xalloc_count); })) /* Other compilers use integer division; this may be slower but is |