为什么用nullPtr调用函数不会使我的应用程序崩溃? [英] Why calling function with nullPtr does not crash my application?

问题描述

我不了解C ++的知识-我在类上创建了一些指针并将其设置为null.

I don't understand something in C++ - I create some pointer on class and set it to null.

现在，我使用此空指针调用某些函数，该函数成功.为什么不崩溃?

Now I call some function with this null pointer and the function succeeds. Why doesn't it crash ?

class Entity
{
public:
    void Print() const
    {
        std::cout << "Print" << std::endl;
    }
};

int main()
{
    Entity* ptr = nullptr;
    Entity& _ref = *ptr;    // No crash here - I expected a null pointer exception

    _ref->Print();  
}

推荐答案

这在C ++中很常见，该函数不是实例的一部分，而是类定义的一部分.

This is a common thing in C++, the function is not part of the instance, but part of the class definition.

如果您尝试访问该函数中的 this ，则将导致崩溃.

If you tried to access this in the function then you would have a crash.

如下面提到的@YSC一样，这被认为是未定义的行为，您不应认为这会起作用.但是它通常可以正常工作，而且我听说这在C ++访谈中甚至被问到了问题.

As @YSC mentioned below, this is considered undefined behavior, and you should not assume this will work. but it will mostly work and i heard this is even asked in C++ interviews questions.

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