一起使用cppcoro和ASIO的co_spawn

html5 • • 问答

我有一个库是使用cppcoro编写的，并希望将它与 ASIO 一起使用。但是每当我尝试co_spawn从所述库中使用协程时。Boost 抱怨 awaitable 类型不正确。

例如：

#include <asio/io_context.hpp>
#include <asio/coroutine.hpp>
#include <asio/co_spawn.hpp>
#include <asio/detached.hpp>
#include <asio/awaitable.hpp>
#include <cppcoro/task.hpp>

cppcoro::task<int> foo()
{
        co_return 1;
}

int main()
{
        asio::io_context ctx;
        asio::co_spawn(ctx, foo(), asio::detached);
        ctx.run();
}

Boost 抱怨cppcoro::task<int>并非源自asio::awaitable

asio_cppcoro.cpp: In function ‘int main()’:
asio_cppcoro.cpp:15:43: error: no matching function for call to ‘co_spawn(asio::io_context&, cppcoro::task<int>, const asio::detached_t&)’
   15 |  asio::co_spawn(ctx, foo(), asio::detached);
      |                                           ^
In file included from /usr/include/asio/co_spawn.hpp:467,
                 from asio_cppcoro.cpp:3:
/usr/include/asio/impl/co_spawn.hpp:199:1: note: candidate: ‘template<class Executor, class T, class AwaitableExecutor, class CompletionToken>  requires  completion_token_for<CompletionToken, void()> auto asio::co_spawn(const Executor&, asio::awaitable<T, AwaitableExecutor>, CompletionToken&&, typename std::enable_if<((asio::is_executor<Executor>::value || asio::execution::is_executor<T>::value) && std::is_convertible<Executor, AwaitableExecutor>::value)>::type*)’
  199 | co_spawn(const Executor& ex,
      | ^~~~~~~~
/usr/include/asio/impl/co_spawn.hpp:199:1: note:   template argument deduction/substitution failed:
asio_cppcoro.cpp:15:43: note:   ‘cppcoro::task<int>’ is not derived from ‘asio::awaitable<T, AwaitableExecutor>’
   15 |  asio::co_spawn(ctx, foo(), asio::detached);

asio_cppcoro.cpp: In function ‘int main()’:
asio_cppcoro.cpp:15:43: error: no matching function for call to ‘co_spawn(asio::io_context&, cppcoro::task<int>, const asio::detached_t&)’
   15 |  asio::co_spawn(ctx, foo(), asio::detached);
      |                                           ^
In file included from /usr/include/asio/co_spawn.hpp:467,
                 from asio_cppcoro.cpp:3:
/usr/include/asio/impl/co_spawn.hpp:199:1: note: candidate: ‘template<class Executor, class T, class AwaitableExecutor, class CompletionToken>  requires  completion_token_for<CompletionToken, void()> auto asio::co_spawn(const Executor&, asio::awaitable<T, AwaitableExecutor>, CompletionToken&&, typename std::enable_if<((asio::is_executor<Executor>::value || asio::execution::is_executor<T>::value) && std::is_convertible<Executor, AwaitableExecutor>::value)>::type*)’
  199 | co_spawn(const Executor& ex,
      | ^~~~~~~~
/usr/include/asio/impl/co_spawn.hpp:199:1: note:   template argument deduction/substitution failed:
asio_cppcoro.cpp:15:43: note:   ‘cppcoro::task<int>’ is not derived from ‘asio::awaitable<T, AwaitableExecutor>’
   15 |  asio::co_spawn(ctx, foo(), asio::detached);

我也尝试将我的协程包装在 a 中asio::awaitable，但没有成功。

编译器抱怨它不能将这两种类型包装在一起

? c++ asio_cppcoro.cpp -o asio_cppcoro -std=c++20 -fcoroutines
asio_cppcoro.cpp: In function ‘asio::awaitable<int> bar()’:
asio_cppcoro.cpp:15:25: error: no matching function for call to ‘asio::detail::awaitable_frame<int, asio::execution::any_executor<asio::execution::context_as_t<asio::execution_context&>, asio::execution::detail::blocking::never_t<0>, asio::execution::prefer_only<asio::execution::detail::blocking::possibly_t<0> >, asio::execution::prefer_only<asio::execution::detail::outstanding_work::tracked_t<0> >, asio::execution::prefer_only<asio::execution::detail::outstanding_work::untracked_t<0> >, asio::execution::prefer_only<asio::execution::detail::relationship::fork_t<0> >, asio::execution::prefer_only<asio::execution::detail::relationship::continuation_t<0> > > >::await_transform(cppcoro::task<int>)’
   15 |  co_return co_await foo();
      |                         ^
In file included from /usr/include/asio/awaitable.hpp:129,
                 from /usr/include/asio/co_spawn.hpp:22,
                 from asio_cppcoro.cpp:3:
/usr/include/asio/impl/awaitable.hpp:150:8: note: candidate: ‘template<class T> auto asio::detail::awaitable_frame_base<Executor>::await_transform(asio::awaitable<T, Executor>) const [with T = T; Executor = asio::execution::any_executor<asio::execution::context_as_t<asio::execution_context&>, asio::execution::detail::blocking::never_t<0>, asio::execution::prefer_only<asio::execution::detail::blocking::possibly_t<0> >, asio::execution::prefer_only<asio::execution::detail::outstanding_work::tracked_t<0> >, asio::execution::prefer_only<asio::execution::detail::outstanding_work::untracked_t<0> >, asio::execution::prefer_only<asio::execution::detail::relationship::fork_t<0> >, asio::execution::prefer_only<asio::execution::detail::relationship::continuation_t<0> > >]’
  150 |   auto await_transform(awaitable<T, Executor> a) const
      |        ^~~~~~~~~~~~~~~
/usr/include/asio/impl/awaitable.hpp:150:8: note:   template argument deduction/substitution failed:
asio_cppcoro.cpp:15:25: note:   ‘cppcoro::task<int>’ is not derived from ‘asio::awaitable<T, asio::execution::any_executor<asio::execution::context_as_t<asio::execution_context&>, asio::execution::detail::blocking::never_t<0>, asio::execution::prefer_only<asio::execution::detail::blocking::possibly_t<0> >, asio::execution::prefer_only<asio::execution::detail::outstanding_work::tracked_t<0> >, asio::execution::prefer_only<asio::execution::detail::outstanding_work::untracked_t<0> >, asio::execution::prefer_only<asio::execution::detail::relationship::fork_t<0> >, asio::execution::prefer_only<asio::execution::detail::relationship::continuation_t<0> > > >’
   15 |  co_return co_await foo();
      |

有没有办法cppcoro::task<>从 ASIO 的 io_context调用基于协程？另外，为什么会发生这种情况？AKAIF C++ 协程是无堆栈的，因此应该可以为任何协程实现生成新的堆栈帧。为什么ASIO阻止我这样做？

编译器：GCC 10.2 ASIO：1.18.1（不是 Boost ASIO。这是独立版本）

以上是一起使用cppcoro和ASIO的co_spawn的全部内容。
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