是抽象的，但具有非虚析构函数.为什么呢?

Question

using namespace std;
class Animal{
public:
virtual void cry() = 0;
void eat();
};

class Cat:public Animal
{
public:
virtual void cry();
void grooming();
};

class Dog:public Animal
{
public:
virtual void cry();
void lash();
};

main()
{
Animal* animal = new Cat();
animal->eat();
animal->cry();
Cat* cat = (Cat*)animal;
cat->grooming();
Dog* dog = new Dog();
dog->cry();
dog->eat();
dog->lash();
delete animal;     //Delete called on'animal' that is abstract but has non-virtual destruct
delete cat;             //Thread 1: signal SIGABRT
delete dog;
}

删除导致错误。为什么呢?尝试在不使用析构函数的情况下通过delete释放内存，但发生错误删除调用抽象但非虚拟破坏的"动物"线程1:信号

Answer 1

错误告诉您问题所在。你正在用非虚构函数销毁虚对象。

你有virtual void cry为什么?这样当你调用animal->cry时，它会调用Cat，而不是默认的Animal。虚析构函数也是如此。当您调用delete animal时，您需要它调用实际对象的析构函数，而不仅仅是基类。您需要添加:

virtual ~Animal() = default;

到你的动物班

基地类析构函数应该是public和virtual，或者是protected和non-virtual

Cpp核心指南

对于第二个问题，双重删除:

delete animal; // deletes the object
delete cat; // deletes the same object again, because cat and animal point to 
// the same place.

有人建议不要删除两次，我建议根本不要显式调用delete。使用智能指针:

auto animal = std::make_unique<Cat>();
Cat &cat = *animal;
animal->cry();
cat.cry(); // Calls the same function as above.

唯一指针将为您处理对象的删除。

Answer 2

您试图删除同一个对象两次:

Animal* animal = new Cat();
Cat* cat = (Cat*)animal;   // cat points to the same object as animal
...
delete animal;     // first delete
delete cat;        // second attemp fails