http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58387
--- Comment #18 from Jeffrey A. Law <law at redhat dot com> --- I'll also note that the plan for the isolated paths that exhibit undefined behaviour is to have them trap/abort at the statement which triggers the undefined behaviour. The original patch from 2011 actually eliminated the undefined behaviour path entirely, that's incorrect in that earlier code in the path might have observable side effects (such as a printf call). It would also make more problems with "optimization unstable code". By unconditionally trapping/aborting at the statement which triggered the undefined behaviour (say a null pointer dereference), we still get any prior observable side effects on the path and we halt the program at the point of undefined behaviour, thus avoiding the multitude of problems around "optimization unstable code".
