vbase10.c

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

// { dg-do compile }
// { dg-options "-Wabi" }

struct A { virtual void f(); char c1; };
struct B { B(); char c2; };
struct C : public A, public virtual B {}; // { dg-warning "ABI" }