TL;医生：

• 工作版本：https://godbolt.org/z/fsxEeGf6W
• 损坏版本（为什么？）：https://godbolt.org/z/KoooxsqoW

我正在编写一个实用函数，它在捕获所有异常的同时 Package std::async。

#include <functional>
#include <future>
#include <iostream>
#include <string>
#include <thread>

namespace Async {

namespace detail {
template <typename F, typename... Args>
std::invoke_result_t<F, Args...> RunWithLogging(std::string label, F&& f,
                                                Args&&... args) {
  try {
    return std::invoke(std::forward<F>(f), std::forward<Args>(args)...);
  } catch (std::exception& ex) {
    std::cout << label << "Exception escaped thread \"" << label
              << "\": " << ex.what();
    throw;
  } catch (...) {
    std::cout << label << "Exception escaped thread \"" << label
              << "\": (non-standard exception type)";
    throw;
  }
}
}  // namespace detail

/// Like std::async(std::launch::async, f, args...):
/// - Catches and logs any escaped exceptions
/// - Returned future joins the thread on destructor
template <typename F, typename... Args>
[[nodiscard]] std::future<std::invoke_result_t<F, Args...>> Launch(
    std::string label, F&& f, Args&&... args) {
  return std::async(
      std::launch::async, [label = std::move(label), f = std::forward<F>(f),
                           ... args = std::forward<Args>(args)]() mutable {
        return detail::RunWithLogging(std::move(label), std::forward<F>(f),
                                      std::forward<Args>(args)...);
      });
}

}  // namespace Async

我想我可以节省几行代码，只使用一个使用async的参数传递签名的函数指针，而不用那个双转发可变lambda：

template <typename F, typename... Args>
[[nodiscard]] std::future<std::invoke_result_t<F, Args...>> Launch(
    std::string label, F&& f, Args&&... args) {
  return std::async(std::launch::async, &detail::RunWithLogging,
                    std::move(label), std::forward<F>(f),
                    std::forward<Args>(args)...);
  ;
}

由于以下原因，该代码无法编译：

C:\...\lib\Async\Thread.h(33,15): error C2672: 'async': no matching overloaded function found [C:\...\build\lib\Async\AsyncTest.vcxproj]
C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.34.31933\include\future(1535,81): message : could be 'std::future<_Select_invoke_traits<decay<_Ty>::type,decay<_ArgTypes>::type...>::type> std::async(_Fty &&,_ArgTypes &&...)' [C:\...\build\lib\Async\AsyncTest.vcxproj]
C:\...\lib\Async\Thread.h(33,15): message : 'std::future<_Select_invoke_traits<decay<_Ty>::type,decay<_ArgTypes>::type...>::type> std::async(_Fty &&,_ArgTypes &&...)': could not deduce template argument for '_ArgTypes &&' from 'overloaded-function' [C:\...\build\lib\Async\AsyncTest.vcxproj]
C:\Program Files\Microsoft Visual Studio\2022\Professional\VC\Tools\MSVC\14.34.31933\include\future(1522,81): message : or       'std::future<_Select_invoke_traits<decay<_Ty>::type,decay<_ArgTypes>::type...>::type> std::async(std::launch,_Fty &&,_ArgTypes &&...)' [C:\...\build\lib\Async\AsyncTest.vcxproj]
C:\...\lib\Async\Thread.h(32,47): message : 'std::future<_Select_invoke_traits<decay<_Ty>::type,decay<_ArgTypes>::type...>::type> std::async(std::launch,_Fty &&,_ArgTypes &&...)': could not deduce template argument for '_Fty' [C:\...\build\lib\Async\AsyncTest.vcxproj]
C:\...\lib\Async\ThreadTest.cpp(24,57): message : see reference to function template instantiation 'std::future<int> Async::Launch<int(__cdecl *)(int),int>(std::string,F &&,int &&)' being compiled [C:\...\build\lib\Async\AsyncTest.vcxproj]
          with
          [
              F=int (__cdecl *)(int)
          ]

我做错什么了？我试过了：

• 将std::decay_t<>添加到invoke_result_t<...>的参数
• 显式指定RunWithLogging的模板参数
• &detail::RunWithLogging或detail::RunWithLogging
• 使用auto返回类型