Embed structures in c

anonstruct.c

#include <stdio.h>

typedef struct point {
    int x, y;
} point;

typedef struct point3d {
    struct point;
    int z;
} point3d;

int main() {
    point p1 = {.x=1, .y=2};
    point3d p2 = {.x=1, .y=2, .z=3};

    printf("%d,%d\n", p1.x, p1.y);
    printf("%d,%d,%d\n", p2.x, p2.y, p2.z);
}