> They exist in CPUs. They exist in configuration. They exist in dependency version mishaps [...] They exist in software assisting with formal methods usage to

> They exist in CPUs. They exist in configuration. They exist in dependency version mishaps [...] They exist in software assisting with formal methods usage too, but what's worse is that frequently implementation is sound and the program still works incorrectly because of erroneous assumptions or bugs in specification. So no, you cannot be sure that your program is bug free without running it... I'm not sure if it is possible to get to being 100% correct in reality - what with cosmic rays altering memory and such...