长度为0的数组—— Arrays of Length Zero

在GNU C中允许声明零长度数组作为扩展。零长度数组可以用作结构的最后一个元素，该数组实际上是可变长度对象的标头。

#include <stdio.h>
int main() {
    struct line {
        int length;
        char contents[0];
    };
    int this_length = 3;
    struct line *thisline = (struct line *) malloc(sizeof(struct line) + this_length);
    thisline->length = this_length;

    thisline->contents[0] = 1;
    thisline->contents[1] = 3;
    thisline->contents[2] = 9;
    for (int i = 0; i < thisline->length; ++i) {
        printf("thisline->contents[%d]:%d\n",i,thisline->contents[i]);
    }

    return 0;

}