[Bug c++/55252] Caret diagnostic doesn't show useful location when macro clashes with name in system header

["dodji at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55252

--- Comment #19 from Dodji Seketeli <dodji at gcc dot gnu.org> ---
(In reply to Tom Tromey from comment #16)
> I've tripped across this enough that I've actually filed dups twice now.
> 
> I think it would be best to change the ordering here.
> That is, the initial error ought to generally be the
> location of the outermost expansion.  Then, the remaining
> notes ought to delineate the macro expansions.
> 
> While it is true that this will yield a sub-optimal result in some
> cases, I think that it will have better results in the preponderance
> of cases.  That is, there's no way to be perfect here but gcc could be more
> useful.


I am starting to think the same here.  In the unwinding, it seems less
surprising to start from the code the user has the most chance to have written
herself, that is, the code at the point of expansion of the outermost macro,
rather than the point where the offending token was spelled -- which can be
hidden anywhere.

If everyone agrees, then I am okay to change the unwinding direction for the
next stage 1.

Manuel, Jonathan, what do you think?