问题描述
我知道在 C++ 中为基类声明虚拟析构函数是一种很好的做法，但是即使对于用作接口的抽象类，声明 virtual 析构函数总是很重要吗?请提供一些原因和示例.
I know it is a good practice to declare virtual destructors for base classes in C++, but is it always important to declare virtual destructors even for abstract classes that function as interfaces? Please provide some reasons and examples why.
推荐答案
对于界面来说，这一点更为重要.你的类的任何用户都可能持有一个指向接口的指针，而不是一个指向具体实现的指针.当他们来删除它时，如果析构函数是非虚拟的，他们将调用接口的析构函数(或编译器提供的默认值，如果您没有指定)，而不是派生类的析构函数.即时内存泄漏.
It's even more important for an interface. Any user of your class will probably hold a pointer to the interface, not a pointer to the concrete implementation. When they come to delete it, if the destructor is non-virtual, they will call the interface's destructor (or the compiler-provided default, if you didn't specify one), not the derived class's destructor. Instant memory leak.
例如
class Interface
{
virtual void doSomething() = 0;
};
class Derived : public Interface
{
Derived();
~Derived()
{
// Do some important cleanup...
}
};
void myFunc(void)
{
Interface* p = new Derived();
// The behaviour of the next line is undefined. It probably
// calls Interface::~Interface, not Derived::~Derived
delete p;
}
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