C语言：strlen()函数易错点

<pre name="code" class="cpp">/*
    strlen函数解析
*/
# include<stdio.h>
# include<malloc.h>
# include<string.h>
 
int main(void)
{
    char * c1 = "AbSjhhss";
    int len1 = strlen(c1);
    printf("len1 = %d\n", len1);     //len1 = 8
 
    char c2[] = {'a', '4', 'r', 't', 'd'};
    int len2 = strlen(c2);
    printf("len2 = %d\n", len2);    //..error..len2 = 9
 
    char c3[] = {'a', '4', 'r', 't', 'd', '\0'};
    int len3 = strlen(c3);
    printf("len3 = %d\n", len3);   //len3 = 5
 
    char c4[10] = "AbS";
    int len4 = strlen(c4);
    printf("len4 = %d\n", len4);   //len4 = 3 
 
    char c5[4];
    int len5 = strlen(c5);
    printf("len5 = %d\n", len5);  //len5 = 5
/*
    c5[0] = '\0';
    len5 = strlen(c5);
    printf("len5 = %d\n", len5);  //len5 = 0
*/
    c5[4] = '\0';
    len5 = strlen(c5);
    printf("len5 = %d\n", len5);  //len5 = 4
 
    return 0;
}
 
/*
    总结：如果字符数组，
       1.用字符串(双引号"")初始化，用strlen函数可以求出该字符串的长度
       2.用字符数组的形式({'',''})初始化，必须在最后面添加一个元素'\0'才可以。
    所以：strlen() 从字符数组首地址开始，一直找下去，直到遇到'\0'才停止
*/