wait_group doesn't build under gcc-12

[anarthal]

The following code:

#include <boost/async/promise.hpp>
#include <boost/async/wait_group.hpp>

static boost::async::promise<void> f()
{
    boost::async::wait_group gp;
    co_return;
}

Doesn't build under GCC12, Linux, Debug. It fails with the following error:

[build] /opt/boost-1.83-dev-with-redis/include/boost/async/detail/select.hpp: In instantiation of ‘static boost::async::detail::fork boost::async::detail::select_ranged_impl<Ct, URBG, Range>::awaitable::await_impl(boost::async::detail::select_ranged_impl<Ct, URBG, Range>::awaitable&, std::size_t) [with boost::asio::cancellation_type Ct = boost::asio::cancellation_type::all; URBG = std::mersenne_twister_engine<long unsigned int, 32, 624, 397, 31, 2567483615, 11, 4294967295, 7, 2636928640, 15, 4022730752, 18, 1812433253>&; Range = std::__cxx11::list<boost::async::promise<void> >&; std::size_t = long unsigned int]’:
[build] /opt/boost-1.83-dev-with-redis/include/boost/async/detail/select.hpp:464:31:   required from ‘bool boost::async::detail::select_ranged_impl<Ct, URBG, Range>::awaitable::await_ready() [with boost::asio::cancellation_type Ct = boost::asio::cancellation_type::all; URBG = std::mersenne_twister_engine<long unsigned int, 32, 624, 397, 31, 2567483615, 11, 4294967295, 7, 2636928640, 15, 4022730752, 18, 1812433253>&; Range = std::__cxx11::list<boost::async::promise<void> >&]’
[build] /opt/boost-1.83-dev-with-redis/include/boost/async/detail/wait_group.hpp:38:34:   required from here
[build] /opt/boost-1.83-dev-with-redis/include/boost/async/detail/select.hpp:385:25: error: ‘operator new’ is provided by ‘std::__n4861::__coroutine_traits_impl<boost::async::detail::fork, void>::promise_type’ {aka ‘boost::async::detail::fork::promise_type’} but is not usable with the function signature ‘static boost::async::detail::fork boost::async::detail::select_ranged_impl<Ct, URBG, Range>::awaitable::await_impl(boost::async::detail::select_ranged_impl<Ct, URBG, Range>::awaitable&, std::size_t) [with boost::asio::cancellation_type Ct = boost::asio::cancellation_type::all; URBG = std::mersenne_twister_engine<long unsigned int, 32, 624, 397, 31, 2567483615, 11, 4294967295, 7, 2636928640, 15, 4022730752, 18, 1812433253>&; Range = std::__cxx11::list<boost::async::promise<void> >&; std::size_t = long unsigned int]’
[build]   385 |     static detail::fork await_impl(awaitable & this_, std::size_t idx)
[build]       |                         ^~~~~~~~~~
[build] In file included from /opt/boost-1.83-dev-with-redis/include/boost/async/gather.hpp:12,
[build]                  from /opt/boost-1.83-dev-with-redis/include/boost/async/detail/wait_group.hpp:13,
[build]                  from /opt/boost-1.83-dev-with-redis/include/boost/async/wait_group.hpp:8,
[build]                  from /home/ruben/workspace/servertech-chat/server/src/listener.cpp:9:
[build] /opt/boost-1.83-dev-with-redis/include/boost/async/detail/gather.hpp: In instantiation of ‘static boost::async::detail::fork boost::async::detail::gather_ranged_impl<Range>::awaitable::await_impl(boost::async::detail::gather_ranged_impl<Range>::awaitable&, std::size_t) [with Range = std::__cxx11::list<boost::async::promise<void> >&; std::size_t = long unsigned int]’:
[build] /opt/boost-1.83-dev-with-redis/include/boost/async/detail/gather.hpp:322:33:   required from ‘bool boost::async::detail::gather_ranged_impl<Range>::awaitable::await_ready() [with Range = std::__cxx11::list<boost::async::promise<void> >&]’
[build] /opt/boost-1.83-dev-with-redis/include/boost/async/detail/wait_group.hpp:90:34:   required from here
[build] /opt/boost-1.83-dev-with-redis/include/boost/async/detail/gather.hpp:281:25: error: ‘operator new’ is provided by ‘std::__n4861::__coroutine_traits_impl<boost::async::detail::fork, void>::promise_type’ {aka ‘boost::async::detail::fork::promise_type’} but is not usable with the function signature ‘static boost::async::detail::fork boost::async::detail::gather_ranged_impl<Range>::awaitable::await_impl(boost::async::detail::gather_ranged_impl<Range>::awaitable&, std::size_t) [with Range = std::__cxx11::list<boost::async::promise<void> >&; std::size_t = long unsigned int]’
[build]   281 |     static detail::fork await_impl(awaitable & this_, std::size_t idx)

It does build under clang-17.

[klemens-morgenstern]

It does build under gcc-13 as well.

[klemens-morgenstern]

@anarthal does this work? https://github.com/klemens-morgenstern/async/tree/gcc-12_workaround

[klemens-morgenstern]

Done.