how to initialize union?

[PRC]

union my_union {
  struct {
    int a;
    int b;
  };
  struct {
    char a;
    short b;
    void *c;
  } v;
};

And I want to initialize 2 global variables, of `my_union' type, A and B to:
------------------------------------
A.a=1; A.b=2;
B.v.a='a'; B.v.b=16; B.v.c=NULL;
------------------------------------
I know how to initialize A by:
union my_union A = { 1, 2 };

But I don't know how to write the initializers for B.
Can gcc support this feature?