Re: [PATCH] c++: Implement -Wdangling-reference [PR106393]

[Marek Polacek <polacek@redhat.com>]

On Tue, Oct 25, 2022 at 12:50:36PM +0100, Jonathan Wakely wrote:
> On Sat, 22 Oct 2022 at 00:28, Marek Polacek wrote:
> > I've run the testsuite/bootstrap with the warning enabled by default.
> > There were just a few FAILs:
> > * g++.dg/warn/Wdangling-pointer-2.C
> > * 20_util/any/misc/any_cast.cc
> > * 20_util/forward/c_neg.cc
> > * 20_util/forward/f_neg.cc
> 
> These two are XFAIL tests, they're checking for a required static
> assert due to misusing std::forward, so I don't think we want to
> change them to remove a "bug" (they're meant to be buggy).
> I think they should use -Wno-dangling-reference

I think we don't have to do anything: -Wdangling-reference is only 
enabled by -Wextra and that isn't used in these tests.  I was just
curious about the warning's impact.

> > * experimental/any/misc/any_cast.cc
> > all of these look like genuine bugs.  A bootstrap with the warning
> > enabled by default passed.
> 
> 
> I've attached a patch for the two any_cast.cc tests that avoids
> creating dangling references, without changing the intended behaviour
> of the tests.

Thanks a lot!

Marek