如果我将一个 char 数组初始化为零/{0}，我是否必须以 null 终止？

Question

例如，我声明了一个 char 数组，其中所有值都设置为零，方式如下：

char array[4] = {0};

如果我给它赋值，例如：

array[0] = 'A';
array[1] = 'B';
array[2] = 'C';

我需要像这样用 null 终止数组吗？:

array[3] = '[=12=]';

或者操作[=13=]是否在任何赋值之前终止？

Answer 1

这个声明

char array[4] = {0};

等同于

char array[4] = { 0, 0, 0, 0 };

来自C标准（6.7.9初始化）

19 The initialization shall occur in initializer list order, each initializer provided for a particular subobject overriding any previously listed initializer for the same subobject;151) all subobjects that are not initialized explicitly shall be initialized implicitly the same as objects that have static storage duration.

和

10 If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static or thread storage duration is not initialized explicitly, then:

— if it has arithmetic type, it is initialized to (positive or unsigned) zero; — if it is an aggregate, every member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; ...

所以元素数组[3]包含0。直到它被覆盖，数组包含一个字符串。

另一种由字符数组的零初始化的方法如下

char array[4] = "";

或以下

char array[4] = { "" };

甚至以下

char array[] = { [3] = '[=14=]' };

这是一个演示程序。

#include <stdio.h>

int main(void) 
{
    char array[] = { [3] = '[=15=]' };
    
    array[0] = 'A';     //  the array contains a string
    
    printf( "%s\n", array );
    
    array[1] = 'B';     //  the array contains a string
    
    printf( "%s\n", array );
    
    array[2] = 'C';     //  the array contains a string
    
    printf( "%s\n", array );
    
    array[3] = 'D';     //  the array does not contain a string
    
    printf( "%.*s\n", ( int )sizeof( array ), array );
    
    
    return 0;
}

程序输出为

A
AB
ABC
ABCD

Answer 2

Do I need to null terminate the array like so?

没有。 '[=10=]' 只是 0 的另一种写法。这是一种编写 self-documenting 代码的方法，专门引用 null 终止符，这超出了传统。（它实际上只是一个写成八进制转义序列的零。）

由于您已经将所有项目设置为 0，因此不需要额外的 [=13=]。

如果我将一个 char 数组初始化为零/{0}，我是否必须以 null 终止？

if I initialize a char array to zero/{0} do I have to null terminate?

c

arrays

initialization

c-strings

null-terminated