c - 关于输出的解释

Question

谁能给我解释输出结果

#include<stdio.h>
int main(void){
    int i;
    char *a[]={ "This is first line",
                "This is second line",
                "This is third line",
                "This is fourth line",
                "This is fifth line",
                "This is sixth line",
                "This is seventh line end"};
    printf("%d\n",sizeof(a));
    printf("%d\n",sizeof(*a[0]));
    for(i=0;i<=sizeof(a[0]);i++){
        printf("%s\n",a[i]);
    }
}

输出:

28
1
This is first line
This is second line
This is third line
This is fourth line
This is fifth line

Answer 1

输出:

28

a是一个包含 7 个指针的数组；每个指针在您的系统上的大小为 4。因此 28。

1

*a与a[0]相同, 所以 a[0][0] , *a[0] , **a和 (*a)[0]都是等价的:都是第一个字符串的第一个字符。

在那之后，你应该得到七行。

This is first line
This is second line
This is third line
This is fourth line
This is fifth line

等等，什么？嗯……

for(i=0;i<=sizeof(a[0]);i++){

对我来说似乎完全错了:

for(i=0;i<sizeof(a)/sizeof(a[0]);i++){

应该会更好。为什么？ i<=sizeof(a[0])是i<=4 , 给出 5 行。

然而，i<sizeof(a)/sizeof(a[0]);是i < 28/4 , 即 7，数组中元素的数量。