双const声明 [英] Double const declaration

问题描述

我经常看到以下函数声明：

I often see the following function declaration:

some_func(const unsigned char * const buffer)
{

}

任何想法为什么const在指针名称之前重复？

Any idea why the const is repeated before the pointer name?

谢谢。

推荐答案

第一个const表示数据指向是不变的，不能改变，第二个表示指针本身不能改变：

The first const says that the data pointed to is constant and may not be changed, the second says that the pointer itself may not be changed:

char my_char = 'z';
const char* a = &my_char;
char* const b = &my_char;
const char* const c = &my_char;

a = &other_char; //fine
*a = 'c'; //error
b = &other_char; //error
*b = 'c'; //fine
c = &other_char; //error
*c = 'c'; //error

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