"Undefined behavior" is not reality; it's a strange shadow world where anything may happen. The compiler reserves the right to reject your reality and substitute its own - which it will not show you within the language, nor let you choose or hint, nor warn you.

People like to use C and C++ as if they were a species of typesafe macro assembler that always produces predictable machine code, and that breaks down often enough that the world is full of systems-level CVEs.