c++ - std::future::get() 不捕获异步函数抛出和程序崩溃时的异常

Question

我正在尝试从使用 std::async 函数开始的函数中调用 future::get() 函数。在我抛出的 async 函数中，我可以在 future::get() 调用中捕获异常。但是，我在 get() 调用中遇到一个异常，该异常未在 catch block 中捕获，并且程序因未处理的异常而崩溃。我错过了什么？

#include "stdafx.h"
#include <iostream>
#include <future>

void AsyncMethodThrowsExceptionTest();
void AsyncMethodThrowsException();

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
    AsyncMethodThrowsExceptionTest();
    return 0;
}


void AsyncMethodThrowsExceptionTest()
{

    std::future<int> executionFuture;

    try
    {
        executionFuture = async(launch::async, AsyncMethodThrowsException);
    }
    catch(...)
    {
        cout << "caught ex [1]";
    }

    std::future_status::future_status status;

    status = executionFuture.wait_for(std::chrono::milliseconds(500u));
    if(status == std::future_status::deferred)
    {
        cout << "AsyncMethodThrowsException has not started";
    }
    else if(status == std::future_status::timeout)
    {
        cout << "AsyncMethodThrowsException timed out";
    }
    else if(status == std::future_status::ready)
    {
        cout << "AsyncMethodThrowsException successfully completed";
        try
        {
            if(executionFuture.valid())
            {
                executionFuture.get();
            }
        }
        catch(const std::future_error& ex)
        {
            cout << "AsyncMethodThrowsExceptionTest catch block";
        }
    }
}

void AsyncMethodThrowsException()
{
    throw(new exception("Exception from AsyncMethodThrowsException"));
}

Answer 1

你不仅在抛出一个指向 std::exception 的指针在 AsyncMethodThrowsException (没有理由这样做)，你们都捕获了对异常的引用而不是指针，以及对 std::exception 的子类的引用在那; std::future::get()抛出被调用函数中抛出的确切异常，而不是 std::future_error .

还有一些其他的语法问题:

• std::future<int> executionFuture应该是 std::future<void> executionFuture
• std::future_status::future_status status应该是 std::future_status status .
• std::exception没有采用 char const* 的构造函数或 std::string ，这可能是一个编译器扩展。

总结一下:

#include <iostream>
#include <future>

void AsyncMethodThrowsExceptionTest();
void AsyncMethodThrowsException();

using namespace std;

int main()
{
  AsyncMethodThrowsExceptionTest();
}


void AsyncMethodThrowsExceptionTest()
{
  std::future<void> executionFuture;

  try
  {
    executionFuture = async(launch::async, AsyncMethodThrowsException);
  }
  catch (...)
  {
    cout << "caught ex [1]";
  }

  std::future_status status = executionFuture.wait_for(std::chrono::milliseconds(500u));
  if (status == std::future_status::deferred)
  {
    cout << "AsyncMethodThrowsException has not started";
  }
  else if (status == std::future_status::timeout)
  {
    cout << "AsyncMethodThrowsException timed out";
  }
  else if (status == std::future_status::ready)
  {
    cout << "AsyncMethodThrowsException successfully completed";
    try
    {
      if(executionFuture.valid())
      {
        executionFuture.get();
      }
    }
    catch(const std::exception& ex)
    {
      cout << "AsyncMethodThrowsExceptionTest catch block";
    }
  }
}

void AsyncMethodThrowsException()
{
  throw runtime_error("Exception from AsyncMethodThrowsException");
}