Eh? I thought that would only be "legal" if it was specified to be implementation-defined behavior. Which would, frankly, be perfectly good. But since it is specified as undefined behavior, programmers are forbidden to use it, and compilers assume it doesn't happen/doesn't exist.
The entire notion that "since this is undefined behavior it does not exist" is the biggest fallacy in modern compilers.
The entire notion that "since this is undefined behavior it does not exist" is the biggest fallacy in modern compilers.