gcc-10: failures in copy-constructors due to [[no_unique_address]].

[williamspatrick]

I am seeing lots of failures in gcc-10 reporting issues with copy-constructors "... is implicitly deleted because the default definition would be ill-formed". This seems to be caused by the use of UNIFEX_NO_UNIQUE_ADDRESS but I'm stumped as to why. (i.e. changing UNIFEX_NO_UNIQUE_ADDRESS to empty allows everything to compile.)

$ cmake -G Ninja -H. -Bbuild -DCMAKE_CXX_FLAGS:STRING=-fcoroutines -DCMAKE_CXX_STANDARD:STRING=20 -DUNIFEX_BUILD_EXAMPLES=yes -DBUILD_TESTING=yes

Using commit 797690d.

$ gcc --version    
gcc (Gentoo 10.3.0-r1 p2) 10.3.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

FAILED: examples/CMakeFiles/never_stream_cancellation.dir/never_stream_cancellation.cpp.o 
/usr/bin/c++  -I../source/../include -Iinclude -fcoroutines -std=gnu++2a -MD -MT examples/CMakeFiles/never_stream_cancellation.dir/never_stream_cancellation.cpp.o -MF examples/CMakeFiles/never_stream_cancellation.dir/never_stream_cancellation.cpp.o.d -o examples/CMakeFiles/never_stream_cancellation.dir/never_stream_cancellation.cpp.o -c ../examples/never_stream_cancellation.cpp
In file included from ../examples/never_stream_cancellation.cpp:21:
../source/../include/unifex/stop_when.hpp: In instantiation of ‘unifex::_stop_when::_op<Source, Trigger, Receiver>::type::type(Source&&, Trigger&&, Receiver2&&) [with Receiver2 = unifex::_sync_wait::_receiver<unifex::_unit::unit>::type; Source = unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&; Trigger = unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&; Receiver = unifex::_sync_wait::_receiver<unifex::_unit::unit>::type]’:
../source/../include/unifex/stop_when.hpp:344:32:   required from ‘unifex::_stop_when::stop_when_operation<decltype (static_cast<Sender&& (*)()noexcept (true)>(nullptr)().*(_memptr<Predecessor>)(static_cast<Sender&& (*)()noexcept (true)>(nullptr)())), decltype (static_cast<Sender&& (*)()noexcept (true)>(nullptr)().*(_memptr<Func>)(static_cast<Sender&& (*)()noexcept (true)>(nullptr)())), typename unifex::remove_cvref<Self>::type> unifex::_stop_when::tag_invoke(unifex::tag_t<unifex::_connect_cpo::connect>, Self&&, Receiver&&) [with Self = unifex::_stop_when::_sndr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type>::type; Receiver = unifex::_sync_wait::_receiver<unifex::_unit::unit>::type; Source = unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type; Trigger = unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type; unifex::_stop_when::stop_when_operation<decltype (static_cast<Sender&& (*)()noexcept (true)>(nullptr)().*(_memptr<Predecessor>)(static_cast<Sender&& (*)()noexcept (true)>(nullptr)())), decltype (static_cast<Sender&& (*)()noexcept (true)>(nullptr)().*(_memptr<Func>)(static_cast<Sender&& (*)()noexcept (true)>(nullptr)())), typename unifex::remove_cvref<Self>::type> = unifex::_stop_when::_op<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&, unifex::_sync_wait::_receiver<unifex::_unit::unit>::type>::type; typename unifex::remove_cvref<Self>::type = unifex::_sync_wait::_receiver<unifex::_unit::unit>::type; decltype (static_cast<Sender&& (*)()noexcept (true)>(nullptr)().*(_memptr<Func>)(static_cast<Sender&& (*)()noexcept (true)>(nullptr)())) = unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&; decltype (static_cast<Sender&& (*)()noexcept (true)>(nullptr)().*(_memptr<Predecessor>)(static_cast<Sender&& (*)()noexcept (true)>(nullptr)())) = unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&; unifex::tag_t<unifex::_connect_cpo::connect> = unifex::_connect_cpo::_fn]’
../source/../include/unifex/tag_invoke.hpp:33:26:   required from ‘constexpr decltype (unifex::_tag_invoke::tag_invoke((CPO&&)(cpo), (Args&&(unifex::_tag_invoke::_fn::operator()::args))...)) unifex::_tag_invoke::_fn::operator()(CPO, Args&& ...) const [with CPO = unifex::_connect_cpo::_fn; Args = {unifex::_stop_when::_sndr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type>::type, unifex::_sync_wait::_receiver<unifex::_unit::unit>::type}; decltype (unifex::_tag_invoke::tag_invoke((CPO&&)(cpo), (Args&&(unifex::_tag_invoke::_fn::operator()::args))...)) = unifex::_stop_when::_op<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&, unifex::_sync_wait::_receiver<unifex::_unit::unit>::type>::type]’
../source/../include/unifex/sender_concepts.hpp:285:32:   required from ‘unifex::_connect_cpo::_fn::_result_t<Sender, Receiver> unifex::_connect_cpo::_fn::operator()(Sender&&, Receiver&&) const [with Sender = unifex::_stop_when::_sndr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type>::type; Receiver = unifex::_sync_wait::_receiver<unifex::_unit::unit>::type; unifex::_connect_cpo::_fn::_result_t<Sender, Receiver> = unifex::_stop_when::_op<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&, unifex::_sync_wait::_receiver<unifex::_unit::unit>::type>::type]’
../source/../include/unifex/sync_wait.hpp:122:27:   required from ‘std::optional<_Tp> unifex::_sync_wait::_impl(Sender&&) [with Result = unifex::_unit::unit; Sender = unifex::_stop_when::_sndr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type>::type]’
../source/../include/unifex/sync_wait.hpp:150:39:   required from ‘std::optional<typename unifex::_if<is_void_v<typename unifex::_if<is_reference_v<typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> > >::apply<std::reference_wrapper<typename std::remove_reference<typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> >::type>, typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> > > >::apply<unifex::_unit::unit, typename unifex::_if<is_reference_v<typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> > >::apply<std::reference_wrapper<typename std::remove_reference<typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> >::type>, typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> > > > unifex::_sync_wait_cpo::_fn::operator()(Sender&&) const [with Sender = unifex::_stop_when::_sndr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type>::type; typename unifex::_if<is_void_v<typename unifex::_if<is_reference_v<typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> > >::apply<std::reference_wrapper<typename std::remove_reference<typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> >::type>, typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> > > >::apply<unifex::_unit::unit, typename unifex::_if<is_reference_v<typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> > >::apply<std::reference_wrapper<typename std::remove_reference<typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> >::type>, typename unifex::_if<is_lvalue_reference_v<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type> >::apply<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type, typename unifex::remove_cvref<typename unifex::sender_traits<typename unifex::remove_cvref<T>::type>::value_types<unifex::single_overload, unifex::single_value_type>::type::type>::type> > > = unifex::_unit::unit]’
../examples/never_stream_cancellation.cpp:47:77:   required from here
../source/../include/unifex/stop_when.hpp:184:76: error: use of deleted function ‘unifex::_reduce::_op<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> >, unifex::_tfx::_receiver<unifex::_stop_when::_srcvr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&, unifex::_sync_wait::_receiver<unifex::_unit::unit>::type>::type, unifex::_for_each::_impl::_reduce>::type>::type::type(const unifex::_reduce::_op<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> >, unifex::_tfx::_receiver<unifex::_stop_when::_srcvr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&, unifex::_sync_wait::_receiver<unifex::_unit::unit>::type>::type, unifex::_for_each::_impl::_reduce>::type>::type&)’
  184 |               unifex::connect((Trigger &&) trigger, trigger_receiver{this})) {}
      |                                                                            ^
In file included from ../source/../include/unifex/for_each.hpp:18,
                 from ../examples/never_stream_cancellation.cpp:17:
../source/../include/unifex/reduce_stream.hpp:239:57: note: ‘unifex::_reduce::_op<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> >, unifex::_tfx::_receiver<unifex::_stop_when::_srcvr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&, unifex::_sync_wait::_receiver<unifex::_unit::unit>::type>::type, unifex::_for_each::_impl::_reduce>::type>::type::type(const unifex::_reduce::_op<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> >, unifex::_tfx::_receiver<unifex::_stop_when::_srcvr<unifex::_tfx::_sender<unifex::_reduce::_sender<unifex::_never::stream, unifex::_unit::unit, unifex::_for_each::_impl::_map<main()::<lambda(auto:45)> > >::type, unifex::_for_each::_impl::_reduce>::type&&, unifex::_tfx::_sender<unifex::_timed_single_thread_context::_schedule_after_sender<std::chrono::duration<long int, std::ratio<1, 1000> > >::type, main()::<lambda()> >::type&&, unifex::_sync_wait::_receiver<unifex::_unit::unit>::type>::type, unifex::_for_each::_impl::_reduce>::type>::type&)’ is implicitly deleted because the default definition would be ill-formed:
  239 | struct _op<StreamSender, State, ReducerFunc, Receiver>::type {
      |                                        

[ericniebler]

And this only happens with gcc-10 when coroutines are enabled? How odd.

[williamspatrick]

This is not caused by coroutines specifically and fails with coroutines disabled as well.

It turns out this is a regression introduced between 10.2 (which is what Github Actions have for gcc-10) and 10.3 and is also present in the 11 series.

• https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98995

The commit which introduced the regression into 10.3 is:

• https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=320054784250e572cb75d6f69ab44b2330d61d8b (11 series +)
• gcc-mirror/gcc@97014e4 (10.3 branch)

The Github Action image has gcc-10 as 10.2 which does not have this regression but some of the coroutine unit tests have SEGVs. I ran with a patch to include/unifex/config.hpp to disable the [[no_unique_address]] and that both compiled and passed unit tests on gcc 10.3.

I plan to submit 1 PR to fix up the config.hpp for GCC 10 to disable [[no_unique_address]] until bug 98995 is fixed.
I plan to submit another PR, if I can figure it out, to the Github Action YAML to update to (at least) gcc 10.3.

[williamspatrick]

It looks like Github is updating the ubuntu image to 10.3 shortly.

actions/runner-images#3665