更改C常量的值 [英] changing const value in C

问题描述

我发现在以下code段

I find that in the following code snippet

const int i = 2;  
const int* ptr1= &i;  
int* ptr2 = (int*)ptr1;  
*ptr2 =3;

I 的值更改为3。我能想知道的是为什么这允许的。什么是在这可能成为有用的情况呢？

i's value changes to 3. What I could like to know is why is this allowed. What are the situations in which this could become helpful?

推荐答案

这是允许的，因为你已经将其转换为一个非const指针否决ptr1的的常量性。这就是为什么强制转换是非常危险的。

It's allowed because you have overruled the constness of ptr1 by casting it to a non-const pointer. This is why casts can be very dangerous.

请注意，一些编译器，如GCC，不会让你抛弃这样的常量状态。

Note that some compilers, such as GCC, will not allow you to cast away const status like this.

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