anon8.c

gcc-you can use this code to learn something about gcc, and inquire further into linux,

// Build don't link:

struct B
{
  int a;
  B & operator= (const B &);
};

struct A
{
  union {
    int a;
  };
  B b;
};

A x;

void foo (const A &y)
{
  x = y;
}