Use memcpy instead of strncpy when we know the length anyway. Modern gcc seems to think it knows how to detect misuse of strncpy, but it's wrong (in fact: very, very wrong) and the path of least resistance is to not try to fight with it.

+
−/* From Al Viro */
+
−#define A(x) B(x)
+
−#define B(x) x
+
−#define C(x) y.C(x)
+
−A(C(z))