https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107532
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|FIXED |---
Status|RESOLVED |ASSIGNED
--- Comment #26 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Kohei Takahashi from comment #24)
> (In reply to Marek Polacek from comment #23)
> > (In reply to Kohei Takahashi from comment #21)
> > > (In reply to Marek Polacek from comment #18)
> > > > (In reply to Barnabás Pőcze from comment #17)
> > > > > The simple test case with std::span still triggers the warning:
> > > > > https://gcc.godbolt.org/z/43cKxdqr3. I feel that without deeper code
> > > > > analysis such a warning will generate too many false positives and
> > > > > people
> > > > > will simply turn it off.
> > > >
> > > > There really haven't been that many, except this and one with
> > > > range-based
> > > > for loops.
> > >
> > > I think it warns many usage of zip_iterator idiom such as boost.iterator
> > > and
> > > P2321 style flat_map. Those uses tuple of references like
> > > std::tuple<T&...>
> > > by dereferencing iterator, so that any algorithms may yield this warning.
> >
> > Ah, would you please have a testcase? If that's the case and the warning
> > can't be taught to recognize that pattern, then I think we need to move it
> > to -Wextra. Thanks.
>
> In my flat map implementation, https://github.com/Flast/flat_map, the
> warning is shown here
> https://github.com/Flast/flat_map/blob/
> f7d547fd4dbde763c07eb8d35796248c41989a66/flat_map/__flat_tree.hpp#LL435C42-
> L435C52 . You can reproduce it by following
> ```
> flat_map$ mkdir build
> flat_map$ cd build
> flat_map/build$ cmake ..
> flat_map/build$ make map_tie_test_17
> ```
>
> `_key_extractor` is defined here,
> https://github.com/Flast/flat_map/blob/
> f7d547fd4dbde763c07eb8d35796248c41989a66/flat_map/flat_map.hpp#L89-L90, and
> the iterator dereference is here,
> https://github.com/Flast/flat_map/blob/
> f7d547fd4dbde763c07eb8d35796248c41989a66/flat_map/tied_sequence.hpp#L67-L72.
> Hence, reduced code is like https://wandbox.org/permlink/DloAyU3dQgydo7PS,
> or https://wandbox.org/permlink/7fM4NDF8u1hiRMFC.
Thanks for those reduced testcases. I may be able to fix the warning there.
