If you statically link the final binary, my point still stands: No translation unit has undefined behavior until the linker statically links them into a binary.

If you statically link the final binary, my point still stands: No translation unit has undefined behavior until the linker statically links them into a binary. (Actually, not until the offending code is run, but if a program can be proved to always trigger undefined behavior you can be a bit loose and say the compiled program has the undefined behavior) Dynamic linking vs. static linking is irrelevant.