[Karellen]

The behaviour is unspecified by the standard.

Your compiler vendor has to pick a (reasonable) behaviour though and apply it consistently, and while they are not required to document it (IIRC - I think that's just for implementation-defined?) you can probably get them to tell you if you have a good support relationship with them. Or you can just figure out what the compiler does, and hope they don't change the behaviour too much with the next release :-)