On 9 Jan 2025, at 20:00, Marek Polacek wrote: > On Thu, Jan 09, 2025 at 12:05:43PM -0500, Patrick Palka wrote: >> On Wed, 8 Jan 2025, Jason Merrill wrote: >> >>> On 12/21/24 11:35 AM, Simon Martin wrote: >>>> When erroring out due to an incomplete type, we add a contextual >>>> note >>>> about the type. However, when the error is suppressed by >>>> -Wno-template-body, the note remains, making the compiler output >>>> quite >>>> puzzling. >>>> >>>> This patch makes sure the note is suppressed if we're processing a >>>> template declaration body with -Wno-template-body. >>>> >>>> Successfully tested on x86_64-pc-linux-gnu. >>>> >>>> PR c++/118163 >>>> >>>> gcc/cp/ChangeLog: >>>> >>>> * cp-tree.h (get_current_template): Declare. >>>> * error.cc (get_current_template): Make non static. >>>> * typeck2.cc (cxx_incomplete_type_inform): Suppress note when >>>> parsing a template declaration with -Wno-template-body. >>> >>> I think rather than adding this sort of thing in lots of places >>> where an error >>> is followed by an inform, we should change error to return bool like >>> other >>> diagnostic functions, and check its return value before calling >>> cxx_incomplete_type_inform or plain inform. This likely involves >>> the same >>> number of changes, but they should be smaller. >>> >>> Patrick, what do you think? >> >> That makes sense to me, it's consistent with the 'warning' API and >> how >> we handle issuing a warning followed by a note. But since the >> -Wtemplate-body mechanism is really only useful for compiling legacy >> code where you don't really care about any diagnostics anyway, and >> the intended way to use it is -fpermissive / -Wno-error=template-body >> rather than -Wno-template-body, I'd prefer a less invasive solution >> that >> doesn't change the API of 'error' if possible. >> >> I wonder if we can work around this by taking advantage of the fact >> that >> notes that follow an error are expected to be linked via an active >> auto_diagnostic_group? Roughly, if we issued a -Wtemplate-body >> diagnostic from an active auto_diagnostic_group then all other >> diagnostics from that auto_diagnostic_group should also be associated >> with -Wtemplate-body, including notes. That way -Wno-template-body >> will >> effectively suppress subsequent notes followed by an eligible error, >> and >> no 'error' callers need to be changed (unless to use >> auto_diagnostic_group). > > FWIW, I love this auto_diagnostic_group idea. Thanks folks, I’ll explore the auto_diagnostic_group idea (and maybe *also* the error returning bool one because I am not a fan of functions that “lie” to their callers :-))
I’ll send a follow-up patch in the coming days. Simon
