C++-面试题：深度拷贝与构造函数中的异常

昨天的一道面试题，分享下：

实现一个拷贝构造函数：

classFoo {                                                                                                                                

public:
  Foo(A* a, B* b);

 ~Foo() {
      delete a;

   delete b;

 }

 

 // Implement copy constructor.

 // Types A and B are Copy Constructible.

private:

 A* a;

 B* b;

};

 

答案：

Foo::Foo(const Foo& other)
{

   this->a = new A(*other.a);

   this->b = new B(*other.b);

}

备注：这道题主要考深度拷贝.

 

 

如果B会抛出异常，该如何处理？

答案：

 

 Foo::Foo(const Foo& other)
{

   this->a = new A(*other.a);

        try{

     this->b =new B(*other.b);

       catch(…)

       {

              delete this->a;

              this->a=nullptr;

       }

}

如果不处理这个异常，会出现什么情况？如果是指针呢？

答案:内存泄露，如果是智能指针则不会出现内存泄露；

 

备注：这道题主要考如下知识点儿：

Objects Are Automatically Destroyed during StackUnwinding

When a block is exited during stack unwinding, the compilerguarantees that objects created in that block are properly destroyed.

If an exception occurs in a constructor, then the object underconstruction might be only partially constructed. Even if the object is onlypartially constructed, we are guaranteed that the constructed members will be properly destroyed.

由于智能指针有自己的析构函数，所以可以自动释放；但是使用new定义的指针就不行了，所以要内存泄露。