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by uecker
7 hours ago
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The check can not be removed if it becomes before the access because in this case the program has no UB. If there were UB, a compiler in C is not allowed to move (time-travel) UB before any observable behavior. This was never allowed by in C (int contrast to C++), but the wording was not clear, which we fixed in C23. If there is no check, you are right that the access itself is UB and there is no requirement to trap in ISO C, but this is something compilers explicitly support.
(and it might be required by POSIX, but I am not sure) |
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