typedef struct { union { int * aaa; } u; } t_a; typedef struct { unsigned bbb : 1; } t_b; typedef struct { int ccc; t_a ddd; t_b eee; int fff; } t_c; typedef struct t_d { t_c f1; t_c f2; } t_d; void foo (void) { t_d ggg; ggg.f1 = ggg.f2; }