> Seeing this purely as a spec v pragmatism issue isn't going to get us anywhere.

That's because it's not.

The spec ( http://pubs.opengroup.org/onlinepubs/009695399/functions/mem... ) explicitly states, "If copying takes place between objects that overlap, the behavior is undefined."

Which means the real debate is between two technically valid interpretations of the spec: one that arbitrarily breaks existing software for no discernible benefit✻, and one that does not.

(✻ Unless, for ideological reasons, one believes that breaking said software is the benefit, in which case this is still a sneaky and passive-aggressive way to go about it.)

It's even fair to cast this particular debate as nonsense vs. pragmatism, because that's what it is.