On Tue, 15 Jul 2025 at 12:26, Jonathan Wakely <jwak...@redhat.com> wrote: > > On Tue, 15 Jul 2025 at 11:57, Luc Grosheintz <luc.groshei...@gmail.com> wrote: > > > > > > > > On 7/14/25 08:57, Tomasz Kaminski wrote: > > > Hi Luc, > > > > > > While running the libc++ test on libstdc++ we have found the following > > > issue in our implementation. > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121061 > > > Would you be interested in looking into fixing this? > > > > Yes, I'll take care of this. Do you know if it's the only issue? > > If it's not clear it might make sense that I learn how to run their > > tests on our code. > > It's very non-trivial and requires some changes to their config. I'm > working on making it easier. > > There are quite a few failures but I haven't analyzed them yet: > > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/aligned_accessor/access.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/aligned_accessor/ctor.conversion.from.default_accessor.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/aligned_accessor/ctor.conversion.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/aligned_accessor/ctor.default.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/aligned_accessor/offset.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/aligned_accessor/operator.conversion.to.default_accessor.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/aligned_accessor/types.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/extents/ctor_from_array.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/extents/ctor_from_span.pass.cpp > stdlib-libstdc++.cfg.in :: std/containers/views/mdspan/extents/dims.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/layout_stride/is_exhaustive_corner_case.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/layout_stride/properties.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/mdspan/ctor.default.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/mdspan/ctor.dh_array.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/mdspan/ctor.dh_span.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/mdspan/index_operator.pass.cpp > stdlib-libstdc++.cfg.in :: > std/containers/views/mdspan/mdspan/properties.pass.cpp
At least the aligned_accessor ones are probably easily explained ;-) > > > > > > > > > > > Also, libc++ makes the default constructor of mdpsan conditionally > > > noexcept > > > as extension > > > (standard does not require it > > > https://eel.is/c++draft/views.multidim#mdspan.mdspan.cons). > > > We could do the same. Instead of writing a big conditional noexcept > > > specification, I would suggest > > > defaultint the constructor on first declaration: > > > constexpr > > > mdspan() > > > requires (rank_dynamic() > 0) > > > && is_default_constructible_v<data_handle_type> > > > && is_default_constructible_v<mapping_type> > > > && is_default_constructible_v<accessor_type> > > > = default; > > > > > > And then having default member initializers: > > > private: > > > [[no_unique_address]] accessor_type _M_accessor = accessor_type(); > > > [[no_unique_address]] mapping_type _M_mapping = mapping_type(); > > > [[no_unique_address]] data_handle_type _M_handle = > > > data_handle_type(); > > > We do not want to use "{}" as the samantis is a bit differnt. > > > > > > > Yes, I think it makes sense if those two implementations behave > > the same. > >
