GCC 中零长数组，C99中的变长数组（VLA）

目录

• GCC 中零长数组
• C99中的变长数组

GCC 中零长数组

GCC 中允许使用零长数组，把它作为结构体的最后一个元素非常有用，下面例子出自 gcc 官方文档。

struct line {
int length;
char contents[0];
};

struct line *thisline = (struct line *) malloc (sizeof (struct line) + this_length);
thisline->length = this_length;

C99中的变长数组

1 #include<stdio.h>
 2 
 3 #define ROWS 3
 4 #define COLS 4
 5 
 6 int sum2d(int rows, int cols, int ar[rows][cols])
 7 {
 8     int i, j, sum;
 9     sum = 0;
10 
11     for(i = 0; i < rows; i++)
12         for(j = 0; j < cols; j++)
13             sum += ar[i][j];
14     return sum;
15 }
16 
17 int main()
18 {
19     int i, j;
20     int junk[ROWS][COLS] = {
21         {2, 4, 6, 8},
22         {3, 5, 7, 9},
23         {12, 10, 8, 6}
24     };
25 
26     int morejunk[ROWS-1][COLS+2] = {
27         {20, 30, 40, 50, 60, 70},
28         {5, 6, 7, 8, 9, 10}
29     };
30     int rs = ROWS;
       int cs = COLS;
31     int varr[rs][cs]; //变长数组
32 
33     for(i = 0; i < rs; i++)
34         for(j = 0; j < cs; j++)
35             varr[i][j] = i * j +j;
36     printf("3 * 5 array\n");
37     printf("sum of all elemts = %d\n",sum2d(ROWS, COLS, junk));
38 
39     printf("2 * 6 array\n");
40     printf("sum of all elemts = %d\n",sum2d(ROWS - 1, COLS + 2, morejunk));
41 
42     printf("3 * 10 array\n");
43     printf("sum of all elemts = %d\n",sum2d(rs, cs, varr));
44 
45     return 0;
46 }

https://www.cnblogs.com/cpoint/p/3368380.html