gcc/testsuite/g++.dg/lto/pr63166_0.ii

// { dg-lto-do compile }
extern "C"
{
  extern long unsigned int strlen (__const char *__s);
}
class Cstring
{
};
class Foobar_Out
{
  virtual void put_to_buf (const char *str, long unsigned int msg_len);
  void put_to_buf (const char *str)
  {
    put_to_buf (str, strlen (str));
  }
  Foobar_Out & operator << (const char *str);
  Foobar_Out & operator << (const Cstring & cstring);
};

class Foobar_Log:public Foobar_Out
{
  Foobar_Log (int channel);
  virtual void put_to_buf (const char *str, long unsigned int msg_len);
};
Foobar_Out & Foobar_Out::operator << (const char *str)
{
  put_to_buf (str);
}

Foobar_Out & Foobar_Out::operator << (const Cstring & cstring)
{
  return *this;
}

Foobar_Log::Foobar_Log (int ch)
{
}