- 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. */
+ 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__