c++ - 如何在 c/c++ 中修复此 "First-chance exception"？

Question

它报告指定了一个无效的句柄。下面的代码:

 if(hPipe)
  CloseHandle(hPipe);

我能做什么？

Answer 1

我怀疑你有这样的事情:

class SmartPipe
{
    HANDLE hPipe;
public:
    //Functions which do something to hPipe
    ~SmartPipe()
    {
        if (hPipe)
            CloseHandle(hPipe);
    }
};

问题是当 SmartPipe 创建时，hPipe 被初始化为随机垃圾。你必须自己初始化它。将 hPipe 添加到类中的初始化列表中:

class SmartPipe
{
    HANDLE hPipe;
public:
    SmartPipe() : hPipe(0)
    {
    }
    //Functions which do something to hPipe
    ~SmartPipe()
    {
        if (hPipe)
            CloseHandle(hPipe);
    }
};

如果这不是您的情况，至少检查 hPipe 是否在某处初始化，即使它被设置为 0 的值也是如此。

编辑:这是一个双重免费场景:

class SmartPipe
{
//As above
};

void SomeFunc(SmartPipe input) //Note pass by value
{  //At this point, the pipe object was copied
   //2 SmartPipes are alive with the same handle value here.
   //Do something with `input`
}

int main()
{
    SmartPipe input;
    //setup input somehow
    SomeFunc(input);
    //Note that at this point the pipe passed by value has already been
    //destroyed, and the handle held by `input` has already been closed.
} //`input` destroyed here, resulting in a double free.

通过使 SmartPipe 不可复制，或为其编写复制句柄的复制构造函数和复制赋值运算符(使用类似 DuplicateHandle 的东西)或引用计数来解决这个问题。