diff options
Diffstat (limited to 'lib/xalloc-oversized.h')
-rw-r--r-- | lib/xalloc-oversized.h | 47 |
1 files changed, 26 insertions, 21 deletions
diff --git a/lib/xalloc-oversized.h b/lib/xalloc-oversized.h index d25596932..4184f3395 100644 --- a/lib/xalloc-oversized.h +++ b/lib/xalloc-oversized.h @@ -2,12 +2,12 @@ Copyright (C) 1990-2000, 2003-2004, 2006-2021 Free Software Foundation, Inc. - This program 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 3 of the License, or - (at your option) any later version. + 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. - 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 Lesser General Public License for more details. @@ -22,33 +22,38 @@ #include <stdint.h> /* True if N * S does not fit into both ptrdiff_t and size_t. - S must be positive and N must be nonnegative. + 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_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_t; -#else -typedef size_t xalloc_count_t; -#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. + + 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)). -/* Return 1 if an array of N objects, each of size S, cannot exist reliably - because its total size in bytes exceeds MIN (PTRDIFF_MAX, SIZE_MAX). - N must be nonnegative, S must be positive, and either N or S should be - of type ptrdiff_t or size_t or wider. 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__ + 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_t) 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_t __xalloc_count; \ + : ({ ptrdiff_t __xalloc_count; \ __builtin_mul_overflow (n, s, &__xalloc_count); })) /* Other compilers use integer division; this may be slower but is |