c++ - 构造函数通过抛出异常结束？是否存在内存泄漏？

Question

我正在检查 this文章 它指出

Note: if a constructor finishes by throwing an exception, the memory associated with the object itself is cleaned up — there is no memory leak. For example:

void f()
{
X x; // If X::X() throws, the memory for x itself will not leak
Y* p = new Y(); // If Y::Y() throws, the memory for *p itself will not leak
}

我很难理解这一点，如果有人能澄清这一点，我将不胜感激。我尝试了以下示例，该示例表明在构造函数内部出现异常时不会调用析构函数。

struct someObject
{
    someObject()
    {
      f = new foo();    
      throw 12;
    }
    ~someObject()
    {
        std::cout << "Destructor of someobject called";
    }

    foo* f;
};

class foo
{
public:
    foo()
    {
            g = new glue();
            someObject a;
    }
    ~foo()
    {
        std::cout << "Destructor of foo";
    }
 private:
  glue* g;
};


int main()
{
    try
    {
        foo a;
    }
    catch(int a)
    {
        //Exception caught. foo destructor not called and someobject destrucotr not called.
       //Memory leak of glue and foo objects
    }
}

我该如何解决这个问题？

对于更新可能造成的不便，我们深表歉意。

Answer 1

"... the destructor would not be called."

由于对象还未被视为已构造，在构造函数因异常而失败后，将不会调用析构函数。

对象分配和构造(仅仅是销毁)是不同的事情。

在抛出异常之前使用 new() 分配的任何对象都将泄漏。

You shouldn't manage these resources yourself, unless you're really, really, really need it, and are about 100% sure about what you're doing.

而是为来自 standard dynamic memory management library 的类成员使用合适的智能指针.