Update from gnulib.

1 files changed, 17 insertions, 2 deletions

diff --git a/lib/xalloc.h b/lib/xalloc.h
index 72400e04a..571e53c04 100644
--- a/lib/xalloc.h
+++ b/lib/xalloc.h
@@ -21,6 +21,9 @@
 # define XALLOC_H_
 
 # include <stddef.h>
+# if HAVE_STDINT_H
+#  include <stdint.h>
+# endif
 
 # ifndef __attribute__
 #  if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8) || __STRICT_ANSI__
@@ -62,8 +65,20 @@ char *xstrdup (const char *str);
 /* 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 an inline function, so that it
-   works correctly even when SIZE_MAX < N.  */
-# define xalloc_oversized(n, s) ((size_t) -1 / (s) < (n))
+   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
+   PTRDIFF_MAX < SIZE_MAX, 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 defined PTRDIFF_MAX && PTRDIFF_MAX < SIZE_MAX
+#  define xalloc_oversized(n, s) (SIZE_MAX / (s) < (n))
+# else /* SIZE_MAX might not be defined, so avoid (SIZE_MAX - 1).  */
+#  define xalloc_oversized(n, s) ((size_t) -2 / (s) < (n))
+# endif
 
 /* These macros are deprecated; they will go away soon, and are retained
    temporarily only to ease conversion to the functions described above.  */