促进：：asio：：产卵是破坏与BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT？

Question

在将boost库从1.71更新到1.74之后，我使用boost::asio::spawn()的代码不使用MSVC2019 (x64为19.25.28612)进行预定义宏BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT的编译。AFAIK，这个宏应该是向后兼容的，我必须使用这个宏，因为我使用了boost::beast::saved_handler，但是它使用了未为建议的标准执行器定义的执行器工作保护。

不仅如此，我的代码成功地使用clang-11 (并定义了BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT)编译。

下面是一个简单的代码示例，它无法使用MSVC2019和Boost.Asio:1.74编译，但将使用Boost.Asio:1.71编译(当然，boost::asio::any_io_executor应该用boost::asio::executor替换)：

#define BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT
#include <boost/asio.hpp>
#include <boost/asio/spawn.hpp>

int main()
{
  boost::asio::io_context ctx;
  boost::asio::any_io_executor executor = ctx.get_executor();
  boost::asio::spawn(executor, [](auto yield){});
  return 0;
}

产出如下：

C:\local\boost_1_74_0\boost/asio/execution/execute.hpp(192): error C2672: 'boost::asio::strand<Executor>::execute': no matching overloaded function found
        with
        [
            Executor=boost::asio::executor
        ]
C:\local\boost_1_74_0\boost/asio/impl/dispatch.hpp(57): note: see reference to function template instantiation 'void asio_execution_execute_fn::impl::operator ()<boost::asio::strand<Executor>,boost::asio::detail::spawn_helper<handler_type,function_type>&>(T &&,F) noexcept(false) const' being compiled
        with
        [
            Executor=boost::asio::executor,
            T=boost::asio::strand<boost::asio::executor>,
            F=boost::asio::detail::spawn_helper<handler_type,function_type> &
        ]
C:\local\boost_1_74_0\boost/asio/async_result.hpp(151): note: see reference to function template instantiation 'void boost::asio::detail::initiate_dispatch::operator ()<boost::asio::detail::spawn_helper<handler_type,function_type>&>(CompletionHandler,void *) const' being compiled
        with
        [
            CompletionHandler=boost::asio::detail::spawn_helper<handler_type,function_type> &
        ]
C:\local\boost_1_74_0\boost/asio/async_result.hpp(363): note: see reference to function template instantiation 'boost::asio::async_result<boost::asio::detail::spawn_helper<handler_type,function_type>,Signature>::return_type boost::asio::async_result<boost::asio::detail::spawn_helper<handler_type,function_type>,Signature>::initiate<Initiation,boost::asio::detail::spawn_helper<handler_type,function_type>&,>(Initiation &&,RawCompletionToken)' being compiled
        with
        [
            Signature=void (void),
            Initiation=boost::asio::detail::initiate_dispatch,
            RawCompletionToken=boost::asio::detail::spawn_helper<handler_type,function_type> &
        ]
C:\local\boost_1_74_0\boost/asio/async_result.hpp(364): note: see reference to function template instantiation 'boost::asio::async_result<boost::asio::detail::spawn_helper<handler_type,function_type>,Signature>::return_type boost::asio::async_result<boost::asio::detail::spawn_helper<handler_type,function_type>,Signature>::initiate<Initiation,boost::asio::detail::spawn_helper<handler_type,function_type>&,>(Initiation &&,RawCompletionToken)' being compiled
        with
        [
            Signature=void (void),
            Initiation=boost::asio::detail::initiate_dispatch,
            RawCompletionToken=boost::asio::detail::spawn_helper<handler_type,function_type> &
        ]
C:\local\boost_1_74_0\boost/asio/impl/dispatch.hpp(212): note: see reference to function template instantiation 'void boost::asio::async_initiate<CompletionToken,void(void),boost::asio::detail::initiate_dispatch,>(Initiation &&,CompletionToken)' being compiled
        with
        [
            CompletionToken=boost::asio::detail::spawn_helper<handler_type,function_type> &,
            Initiation=boost::asio::detail::initiate_dispatch
        ]
C:\local\boost_1_74_0\boost/asio/impl/spawn.hpp(452): note: see reference to function template instantiation 'void boost::asio::dispatch<boost::asio::detail::spawn_helper<handler_type,function_type>&>(CompletionToken)' being compiled
        with
        [
            CompletionToken=boost::asio::detail::spawn_helper<handler_type,function_type> &
        ]
C:\local\boost_1_74_0\boost/asio/impl/spawn.hpp(493): note: see reference to function template instantiation 'void boost::asio::spawn<boost::asio::executor_binder<void (__cdecl *)(void),boost::asio::strand<Executor>>,Function>(Handler &&,Function &&,const boost::coroutines::attributes &,void *)' being compiled
        with
        [
            Executor=boost::asio::executor,
            Function=main::<lambda_c142a977195366454fba7e579637857b>,
            Handler=boost::asio::executor_binder<void (__cdecl *)(void),boost::asio::strand<boost::asio::executor>>
        ]
C:\local\boost_1_74_0\boost/asio/impl/spawn.hpp(483): note: see reference to function template instantiation 'void boost::asio::spawn<Function,Executor>(const boost::asio::strand<Executor> &,Function &&,const boost::coroutines::attributes &)' being compiled
        with
        [
            Function=main::<lambda_c142a977195366454fba7e579637857b>,
            Executor=boost::asio::executor
        ]
C:\Users\Artem Suleimanov\CLionProjects\test\main.cpp(10): note: see reference to function template instantiation 'void boost::asio::spawn<main::<lambda_c142a977195366454fba7e579637857b>,boost::asio::executor>(const Executor &,Function &&,const boost::coroutines::attributes &,void *)' being compiled
        with
        [
            Executor=boost::asio::executor,
            Function=main::<lambda_c142a977195366454fba7e579637857b>
        ]
C:\local\boost_1_74_0\boost/asio/execution/execute.hpp(192): error C2893: Failed to specialize function template 'enable_if<boost::asio::execution::can_execute<const Executor&,Function>::value,void>::type boost::asio::strand<Executor>::execute(Function &&) const'
        with
        [
            Executor=boost::asio::executor
        ]
C:\local\boost_1_74_0\boost/asio/strand.hpp(276): note: see declaration of 'boost::asio::strand<Executor>::execute'
        with
        [
            Executor=boost::asio::executor
        ]
C:\local\boost_1_74_0\boost/asio/execution/execute.hpp(192): note: With the following template arguments:
C:\local\boost_1_74_0\boost/asio/execution/execute.hpp(192): note: 'Function=boost::asio::detail::spawn_helper<handler_type,function_type> &'

那是编译器/boost bug，还是我做错了什么？

Answer 1

看来这个问题是固定的。我应用了现在由MSVC2019编译的修补程序和代码。

此修补程序的THe发布说明条目：

• 修正了针对较旧的strand<>版本或不太符合C++的编译器时网络TS执行器的C++适配。