Linux c：零長數組

一、零長數組

    GNU C容許聲明長度爲零的數組，但它只能被用於結構體的最後一個成員。

 

實例：

#include <stdio.h>
#include <stdlib.h>

typedef struct pos
{
    double lon;
    double lat;
}tPos;
 
struct line {
    int length;
     tPos pos[0];
};
 
int main(void)
{
    int i, count = 9;
    
    struct line *thisline = (struct line *)malloc(sizeof(int) + sizeof(tPos)* count + 1);
    
    thisline->length = count;
    for (i = 0; i < count; i++)
    {
        thisline->pos[i].lon =  121.175581 - i;
        thisline->pos[i].lat =  31.567345 + i;
    
    }
       
    
    printf("sizeof(struct line) = %d\n", sizeof(struct line));
    
    for (i = 0; i < thisline->length; i++)
    {
        printf("thisline->pos[%d].lon = %f\n", i,thisline->pos[i].lon);
        printf("thisline->pos[%d].lat = %f\n", i,thisline->pos[i].lat);

    }

    
    return 0;
}

輸出：

sizeof(struct line) = 8
thisline->pos[0].lon = 121.175581
thisline->pos[0].lat = 31.567345
thisline->pos[1].lon = 120.175581
thisline->pos[1].lat = 32.567345
thisline->pos[2].lon = 119.175581
thisline->pos[2].lat = 33.567345
thisline->pos[3].lon = 118.175581
thisline->pos[3].lat = 34.567345
thisline->pos[4].lon = 117.175581
thisline->pos[4].lat = 35.567345
thisline->pos[5].lon = 116.175581
thisline->pos[5].lat = 36.567345
thisline->pos[6].lon = 115.175581
thisline->pos[6].lat = 37.567345
thisline->pos[7].lon = 114.175581
thisline->pos[7].lat = 38.567345
thisline->pos[8].lon = 113.175581
thisline->pos[8].lat = 39.567345

 

注意：在分配空間大小時，須要分配足夠的大小，不然結果可能爲隨機數據；

跨平臺使用時，不必定可移植