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

[manu at gcc dot gnu.org]

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

--- Comment #3 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2012-11-10 
22:58:16 UTC ---
Hum, I am not sure why the macro unwinder avoids unwinding if the macro comes
from a system-header. If a warning message comes from a system-header, then it
should have been suppressed earlier and never reach the macro unwinder.
Otherwise, we already have emitted the diagnostic, so the macro unwinder just
provides more context.