C struct embedding

test.c

// gcc -std=c99 -Wall -s -O3 -fms-extensions -Wno-microsoft-anon-tag -o test test.c
// clang -std=c99 -Wall -s -O3 -fms-extensions -Wno-microsoft-anon-tag -o test test.c

#include <stdio.h>

typedef struct
{
    unsigned a;
} A;

typedef struct
{
    unsigned b;
} B;

typedef struct
{
    union {
        A;
        A A;
    };
    union {
        B;
        B B;
    };
} AB;

static void A_print(A *a) {
    printf("a: %u\n", a->a);
}

static void B_print(B *b) {
    printf("b: %u\n", b->b);
}

static void AB_print(AB *ab) {
    A_print(&ab->A);
    B_print(&ab->B);
}

int main(int argc, char **argv)
{
    AB ab;
    ab.A.a = 5;
    ab.b = 10;
    AB_print(&ab);

    return 0;
}