If some of the things that the C standard left undefined had instead been made implementation defined then the compiler would at least be obligated to do something that makes sense on the target architecture, rather than having license to take the lawful-evil route. (Plenty of architectures have addressable RAM at location zero, for instance.)

For some reason this always brings to mind that moment in Red Dwarf where Kryten, devoid of his behavioural chip, deems it appropriate to serve roast human to his crewmates. "If you eat chicken, obviously you'd eat your own species as well, otherwise you'd just be picking on the chickens!"

Both C and C++ compilers (in fact, they share this part) very aggressively exploited undefined behavior for performance. But I this was certainly not adversarial. Programmers also regularity picked optimizations over safety. I think nowadays the unsafety of C with modern tooling vs the safety of - say - Rust is very much exaggerated.