In practice this type of over-read is not uncommon in library code (even for standard routines), but I haven't seen compilers generate it. False positives with

In practice this type of over-read is not uncommon in library code (even for standard routines), but I haven't seen compilers generate it. False positives with memory-sanitizers is definitely a problem: the hand-rolled library uses can be whitelisted, but that's not feasible once the compiler starts generating it in arbitrary code.