[taneq]

> You are no longer using C, you are using <Implementation>C.

This is always the case because the C standard is only a partial spec. There's no such thing as "a program written in C(++)", there's only "a program written in <Implementation> C(++)". If you compile your program with a different implementation, then it's a different program. It may work, but it may not.

What I'd really like to see is a modified version of the C/C++ standards which keeps the language the same "in spirit" but removes all undefined and implementation-dependent behaviour. This would give compiler writers a stationary (or at least slower-moving) target to aim for and make it possible for C to be portable in theory as well as (sorta) in practice.