m3.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

// Build don't link: 

struct A { A() { a = 2; } int a; };

struct B {
  struct A { A() { a = 2; } int a; };
  A aa;
};
char xx[]="../tests/m3.cc:4: redefinition of `struct A'";