[Bug lto/62026] [4.9/5 Regression] Crash in lto_get_decl_name_mapping

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62026

--- Comment #13 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
A bit more reduced (just testing upcoming creduce release):

class C;
class F {
  virtual C m_fn1();
};
class C {
 public:
  virtual int *m_fn3(int);
};
class G : F, C {
  int offsets;
  int *m_fn3(int);
};
C *a;
int *G::m_fn3(int) {
  if (offsets) return 0;
}

void fn1() {
  for (;;) a->m_fn3(0);
}