“纯虚函数调用"在哪里?崩溃从何而来?

Where do quot;pure virtual function callquot; crashes come from?(“纯虚函数调用在哪里?崩溃从何而来?)

问题描述

我有时会注意到程序在我的计算机上崩溃并显示错误:纯虚函数调用".

I sometimes notice programs that crash on my computer with the error: "pure virtual function call".

当无法从抽象类创建对象时，这些程序如何编译?

How do these programs even compile when an object cannot be created of an abstract class?

推荐答案

如果您尝试从构造函数或析构函数调用虚函数，可能会导致这些问题.由于您不能从构造函数或析构函数调用虚函数(派生类对象尚未构造或已被销毁)，因此它调用基类版本，在纯虚函数的情况下，不会'不存在.

They can result if you try to make a virtual function call from a constructor or destructor. Since you can't make a virtual function call from a constructor or destructor (the derived class object hasn't been constructed or has already been destroyed), it calls the base class version, which in the case of a pure virtual function, doesn't exist.

(查看现场演示这里)

class Base
{
public:
    Base() { doIt(); }  // DON'T DO THIS
    virtual void doIt() = 0;
};

void Base::doIt()
{
    std::cout<<"Is it fine to call pure virtual function from constructor?";
}

class Derived : public Base
{
    void doIt() {}
};

int main(void)
{
    Derived d;  // This will cause "pure virtual function call" error
}

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