+#ifndef timersub
+/* This is a copy from GNU C Library (GNU LGPL 2.1), sys/time.h. */
+# define timersub(a, b, result) \
+ do { \
+ (result)->tv_sec = (a)->tv_sec - (b)->tv_sec; \
+ (result)->tv_usec = (a)->tv_usec - (b)->tv_usec; \
+ if ((result)->tv_usec < 0) { \
+ --(result)->tv_sec; \
+ (result)->tv_usec += 1000000; \
+ } \
+ } while (0)
+#endif