当我调用一个NULL对象指针的成员函数时会发生什么？ [英] What will happen when I call a member function on a NULL object pointer?

问题描述

我作为面试问题给了以下信息：

  A类
 {
 public： 
 void fun（）
 {
 std :: cout< fun< std :: endl; 
} 
}; 
 
 A * a = NULL; 
 a-> fun（）; 
  

执行此代码时会发生什么，为什么？

---

另请参阅：

• 当在null实例上调用成员函数时，未定义的行为？

解决方案

这是未定义的行为， / p>

一个可能的结果是它只打印fun，因为该方法不访问任何成员变量它被调用的对象（不需要访问对象应该存在的内存，因此不一定会发生访问冲突）。

I was given the following as an interview question:

class A
{
public:
    void fun()
    {
        std::cout << "fun" << std::endl;
    }
};

A* a = NULL;
a->fun();

What will happen when this code is executed, and why?

---

See also:

• When does invoking a member function on a null instance result in undefined behavior?

解决方案

It's undefined behavior, so anything might happen.

A possible result would be that it just prints "fun" since the method doesn't access any member variables of the object it is called on (the memory where the object supposedly lives doesn't need to be accessed, so access violations don't necessarily occur).

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