[makomk]

The "hostile opponent" analogy is a good one. C was always intended as a kind of higher-level replacement for assembly, so it was reasonable to assume (for instance) that uninitialized integer variables contain some unspecified but definite value, but recently compilers have been deliberately breaking those assumptions just because they can. It's almost reached the point where C isn't useful for its original purpose of systems programming; it's very hard to write threaded code that doesn't rely on undefined behaviour, for instance.