+/* Some of the code in this file assumes that signed integer overflow
+ silently wraps around. This assumption can't easily be programmed
+ around, nor can it be checked for portably at compile-time or
+ easily eliminated at run-time.
+
+ Define WRAPV to 1 if the assumption is valid and if
+ #pragma GCC optimize ("wrapv")
+ does not trigger GCC bug 51793
+ <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51793>.
+ Otherwise, define it to 0; this forces the use of slower code that,
+ while not guaranteed by the C Standard, works on all production
+ platforms that we know about. */
+#ifndef WRAPV
+# if (((__GNUC__ == 4 && 4 <= __GNUC_MINOR__) || 4 < __GNUC__) \
+ && defined __GLIBC__)
+# pragma GCC optimize ("wrapv")
+# define WRAPV 1
+# else
+# define WRAPV 0
+# endif
+#endif
+