It's Undefined Behavior by the C standard. So GCC (or other compiler) could use that for optimization, and omit the relevant lines or otherwise mess things up i

It's Undefined Behavior by the C standard. So GCC (or other compiler) could use that for optimization, and omit the relevant lines or otherwise mess things up in weird ways. There's no guarantee that you'll notice, and no need for the identifier to be used by the host environment for it to cause a problem. That said, I'm not aware of any current compiler that does this. It'd be weird.