Undefined Behaviour as usual

Posted Mar 1, 2024 16:34 UTC (Fri) by farnz (subscriber, #17727)
In reply to: Undefined Behaviour as usual by pizza
Parent article: Stenberg: DISPUTED, not REJECTED

OTOH, while the behavior of that off-by-one read is truly unknowable from C's perspective, if the developer "corrects" the bug by incrementing the array size by one (therefore making it too large for the hw resource) the program is now "correct" from C's perspective, but will trigger the same nasty consequences on the actual hardware.

I spend a lot of time in the land of qualified compilers, where the compiler promises that as long as you stick to the subset of the language that's qualified, you can look only at the behaviours evident in the source code to determine what the binary will do. You're expected, if you're working in this land, to have proper code review and separate code audit processes so that a fix of the type you describe never makes it to production, since it's obvious from the source code that the program, while "correct" from C's perspective, is incorrect from a higher level perspective.

And a lot of the problems I see with the way UB is handled feel like people expect all compilers to behave like qualified compilers, not just on a subset of the language, but on everything, including UB.