混合c ++异常处理和SEH（窗口） [英] intermixing c++ exception handling and SEH (windows)

问题描述

我有一个函数，我调用 getaddrinfo（）获取一个 sockaddr * 哪个目标内存被分配由系统。
许多人知道，你需要调用$ code freeaddrinfo（）来释放由getaddrinfo（）分配的内存。

现在，在我的函数中，有几个地方，我可能会抛出一个异常，因为一些函数失败。
我的第一个解决方案是将 freeaddrinfo（）并入每个if-block。
但是对我而言看起来很丑，因为在函数返回之前我不得不打电话给我，所以我想出了SEH的try-finally ...

但我遇到的问题是，不允许将throw语句编入__try-block

然后，我在msdn上阅读并尝试将throw语句交换到从__try-block ...中调用的帮助函数中，而且，编译器不再呻吟了...

代码：

  void function（）
 {
 // ... 
 addrinfo * pFinal; 
 __try 
 {
 getaddrinfo（...，& pFinal）; 
 
 // if（DoSomething1（）== FAILED）
 // throw（exception）; //错误C2712：在需要对象展开的函数中不能使用__try 
 
 //但是这个工程
 Helper（）; 
 
 
 // ... 
 
} 
 __finally 
 {
 freeaddrinfo（）; 
} 
} 
 
 
 void Helper（）
 {
 throw（Exception）; 
} 
  

编辑：

尝试以下，它可以抛出一个整数，但不是当我使用一个类作为一个例外：

  class X 
 {
 public：
 X（）{}; 
〜X（）{}; 
}; 
 
 
 void Helper（）
 {
 throw（X（））; 
} 
 
 
 void base（）
 {
 __try 
 {
 std :: cout<< 输入__try\\\
; 
 
 Helper（）; 
 
 std :: cout<<< 离开__try\\\
; 
} 
 __finally 
 {
 std :: cout<<< 在__finally\\\
; 
} 
}; 
 
 
 int _tmain（int argc，_TCHAR * argv []）
 {
 try 
 {
 base（）; 
} 
 catch（int& X）
 {
 std :: cout<< 抓到X<的std :: ENDL; 
} 
 
 std :: cin.get（）; 
 return 0; 
} 
  

为什么？ ：/

解决方案

您可以将addrinfo包装在调用 getaddrinfo 在构造函数中和 freeaddrinfo 中的析构函数。

这样它总是被释放，无论是否抛出异常。

I have a function in which I call getaddrinfo() to get an sockaddr* which targets memory is allocated by the system. As many may know, you need to call freeaddrinfo() to free the memory allocated by getaddrinfo().

Now, in my function, there are a few places, where I may throw an exception, because some function failed. My first solution was to incorporate the freeaddrinfo() into every if-block. But that did look ugly for me, because I would have had to call it anyways before my function returns, so I came up with SEH`s try-finally...

But the problem I encountered is, that it is not allowed to code the throw-statements into the __try-block

Then, I read on the msdn and tried to swap the throw-statements into the helper function called from within the __try-block... and voila, the compiler didn´t moan it anymore...

Why is that? And is this safe? This does not make sense to me :/

Code:

void function()
{
    //...
    addrinfo* pFinal;
    __try
    {
        getaddrinfo(..., &pFinal);

        //if(DoSomething1() == FAILED)
        //  throw(exception);           //error C2712: Cannot use __try in functions that require object unwinding

        //but this works
        Helper();


        //...

    }
    __finally
    {
        freeaddrinfo();
    }
}


void Helper()
{
    throw(Exception);
}

EDIT:

tried the following and it works with throwing an integer, but does not when i use a class as an exception:

class X
{
public:
    X(){};
    ~X(){};
};


void Helper()
{
    throw(X());
}


void base()
{
    __try
        {
            std::cout << "entering __try\n";

            Helper();

            std::cout << "leaving __try\n";
        }
        __finally
        {
            std::cout << "in __finally\n";
        }
};


int _tmain(int argc, _TCHAR* argv[])
{
    try
    {
        base();
    }
    catch(int& X)
    {
        std::cout << "caught a X" << std::endl;
    }

    std::cin.get();
    return 0;
}

Why? :/

解决方案

You could wrap the addrinfo in a class that calls getaddrinfo in the constructor and freeaddrinfo in its destructor.

That way it will always be freed, whether there is an exception thrown or not.

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