c++ - RAII 失败 - 为什么此 C++ 代码会泄漏？ - 在 try block 中放入 ctor 可防止 dtor

Question

下面程序的输出是:

begin try
Object() ctor
begin catch

为什么不调用 Holder 类的析构函数？这是内存泄漏吗？是否可以在不重新抛出的情况下调用 Holder 类的析构函数？

#include <iostream>
#include <exception>


class Object
{
public:
    Object() { std::cout << "Object() ctor" << std::endl; }
    ~Object() { std::cout << "~Object() dtor" << std::endl; }
};

class Holder
{

public:
    Holder() :myObjectP( new Object() )
    {
        throw std::exception();
    }
    ~Holder()
    {
        std::cout << "~Holder()" << std::endl;
        delete myObjectP;
    }
private:
    Object* myObjectP;

};

int main(int argc, char* argv[])
{
    try
    {
        std::cout << "begin try" << std::endl;
        Holder h;
    }
    catch ( ... )
    {
        std::cout << "begin catch" << std::endl;
    }
    return 0;
}

Answer 1

在这种情况下，您的Holder 对象h 没有完全构建，也就是说h 的构造函数之前没有完成构建堆栈展开过程已经开始。

C++11 15.2 Constructors and destructors(2)

An object of any storage duration whose initialization or destructionis terminated by an exception will have destructors executed for allof its fully constructed subobjects (excluding the variant members ofa union-like class), that is, for subobjects for which the principalconstructor (12.6.2) has completed execution and the destructor hasnot yet begun execution.