[RFA] Silence some warnings [was Re: "introduce no new bootstrap..."]

[Neil Booth]

Zack Weinberg wrote:-

> We can live with some level of false positives.  In the long term I
> want to see more information carried downstream with each token:
> at least the file it came from and the position within.

:-(

This is serious overhead, and further bloating of the token structure.
We don't deal with token pointers in cpplib (and we know where that
took us :-)), but with token objects --- and we do quite a lot of
(mostly unavoidable) token copying.

> This isn't just for warning suppression.  One of the secondary
> goals of cpplib was so we could issue diagnostics and emit debug
> info inside complex macros, that referred to the real location of
> the source code.

Is this really worth it?  We can print a macro stack with minimal
effort with existing code, and along with -E and -dD that should be
verbose enough for even the meanest intelligence to figure out :-)

Does DWARF2 or whatever have the ability to take all this info?  I
hate to think of the size that debug info would become.
 
> I don't know what Mark's reaction will be, but my attitude is that
> overzealous warnings are a bug, so the patch qualifies as a bug fix.
> It's not hugely invasive and doesn't affect code generation, either.

I agree, but I'd like him to give it the thumbs up anyway.

Thanks,

Neil.