Some tests in gcc.c-torture rely on undefined behaviour?

[Nicholas Nethercote]

On Tue, 12 Jul 2005, Joseph S. Myers wrote:

>> My question is:  what exactly is gcc.c-torture testing?  It seems to be
>
> That GNU C code compiles or executes as expected for GNU C.

Is there a definition for GNU C?  implement-c.texi and extend.texi have 
some information about this, are there any other sources?

Thanks.

Nick