/* xalloc-oversized.h -- memory allocation size checking
- Copyright (C) 1990-2000, 2003-2004, 2006-2016 Free Software Foundation, Inc.
+ Copyright (C) 1990-2000, 2003-2004, 2006-2018 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
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 <http://www.gnu.org/licenses/>. */
+ 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>
-#ifndef __has_builtin
-# define __has_builtin(x) 0
+/* 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 due
- to size 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.
+/* 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. */
- By gnulib convention, SIZE_MAX represents overflow in size
- calculations, so the conservative dividend to use here is
- SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
- However, malloc (SIZE_MAX) fails on all known hosts where
- sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
- exactly-SIZE_MAX allocations on such hosts; this avoids a test and
- branch when S is known to be 1. */
-#if 5 <= __GNUC__ || __has_builtin (__builtin_mul_overflow)
+#if 7 <= __GNUC__
# define xalloc_oversized(n, s) \
- ({ size_t __xalloc_size; __builtin_mul_overflow (n, s, &__xalloc_size); })
-#else
+ __builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1)
+#elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__
# define xalloc_oversized(n, s) \
- ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
+ (__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_ */