std :: future :: get（）在異步函數拋出和程序崩潰時無法捕獲異常

Question

我想從使用std :: async函數啓動的函數調用future :: get（）函數。在異步函數中，我正在拋出，以便在將來的:: get（）調用中捕獲異常。然而，我在get（）調用中遇到了一個異常，這個異常在捕獲塊中沒有被捕獲，並且程序因unhandeld異常而崩潰。我錯過了什麼？

#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

你不僅是在AsyncMethodThrowsException扔一個指向std::exception（沒有理由這樣做），你兩個捕獲到異常不是一個指針引用，併爲子類的引用std::exception在那; std::future::get()拋出被調用函數中拋出的確切異常，而不是std::future_error。

有一對夫婦的其他語法問題：

• std::future<int> executionFuture應該std::future<void> executionFuture
• std::future_status::future_status status應該std::future_status status。
• std::exception沒有一個構造函數需要char const*或std::string，這可能是一個編譯器擴展。

總結的事情了：

#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"); 
}