在什么地方“纯虚拟函数调用”崩溃来自？

问题描述

我有时会注意到程序在我的电脑上崩溃时出现错误：纯虚函数调用。

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

这些程序在无法创建对象时一个抽象类？

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

推荐答案

如果你尝试从构造函数或析构函数调用虚函数，因为你不能从构造函数或析构函数中调用虚函数（派生类对象没有被构造或者已经被销毁），它调用基类版本，在纯虚函数的情况下，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.

（请参阅实时演示）

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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