GCC and pointer overflows

Of course it's best if we all stick to the standard, but people do make mistakes.
I think the simplest way to minimize this is to have an attribute marking the check as a
safty/sanity check so the compiler knows that:
1. It should not optimize this check out.
2. If it knows that this check will allways fail it can emit a warning.
3. If this check is assuming something improper it's better to fail the compilation and let
the coder look up the error somewhere, than to silently drop the test.