“纯虚函数调用"在哪里?崩溃从何而来?
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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