https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107532
--- Comment #24 from Kohei Takahashi <flast at flast dot jp> --- (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.
