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authorPaul Eggert <eggert@cs.ucla.edu>2015-11-13 12:39:13 -0800
committerPaul Eggert <eggert@cs.ucla.edu>2015-11-13 12:40:52 -0800
commit92a501022e0154cd9de41240680b7f003a833c96 (patch)
treed4cee238be4fd88bd254ebd9f348971e6b749b78 /lib
parent04ac097f34d887e1ae8dea1e884118728e931c7a (diff)
downloademacs-92a501022e0154cd9de41240680b7f003a833c96.tar.gz
Merge from gnulib
This incorporates: 2015-11-13 xalloc-oversized: improve performance with GCC 5 * lib/xalloc-oversized.h: Copy from gnulib.
Diffstat (limited to 'lib')
-rw-r--r--lib/xalloc-oversized.h13
1 files changed, 11 insertions, 2 deletions
diff --git a/lib/xalloc-oversized.h b/lib/xalloc-oversized.h
index f0e9778f738..0e579deb2bb 100644
--- a/lib/xalloc-oversized.h
+++ b/lib/xalloc-oversized.h
@@ -16,9 +16,13 @@
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef XALLOC_OVERSIZED_H_
-# define XALLOC_OVERSIZED_H_
+#define XALLOC_OVERSIZED_H_
-# include <stddef.h>
+#include <stddef.h>
+
+#ifndef __has_builtin
+# define __has_builtin(x) 0
+#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
@@ -32,7 +36,12 @@
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)
+# define xalloc_oversized(n, s) \
+ ({ size_t __xalloc_size; __builtin_mul_overflow (n, s, &__xalloc_size); })
+#else
# define xalloc_oversized(n, s) \
((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
+#endif
#endif /* !XALLOC_OVERSIZED_H_ */