Const Struct 与 Const 成员的结构

Question

这两个有区别吗？

typedef struct {
    unsigned int day;
    unsigned int month;
    unsigned int year;
}birthday_t;

typedef struct {
    const birthday_t birthday;
    const unsigned int id;
}person_t;

person_t person = {
    .birthday = {1,20,2000},
    .id = 123};

和

typedef struct {
    unsigned int day;
    unsigned int month;
    unsigned int year;
}birthday_t;

typedef struct {
    birthday_t birthday;
    unsigned int id;
}person_t;

const person_t person = {
    .birthday = {1,20,2000},
    .id = 123};

如果结构内的成员是 const 但结构不是常量（上），这与没有常量成员的 const 结构（下）是否不同？

Answer 1

主要区别在于意图之一。

typedef struct {
    const birthday_t birthday;
    const unsigned int id;
}person_t;

说没有 person_t 可以改变它的 birthday 或 id。

const person_t person = {
    .birthday = {1,20,2000},
    .id = 123};

（假设 person_t 的第二个声明）说这个特定的人不能改变它的 birthday 或 id，但其他人的对象可能。

Answer 2

在这里你让所有人都必须有常量（生日和身份证）

typedef struct {
    const birthday_t birthday;
    const unsigned int id;
}person_t;
```````````````````
but here you made one person struct should be constant but other not
```````````````
const person_t person = {
    .birthday = {1,20,2000},
    .id = 123};
``````````

Const Struct 与 Const 成员的结构

Const Struct vs Struct With Const Members

c

struct

constants

c99