llvm-project/clang/test/CodeGenCXX/2006-10-30-ClassBitfield.cpp

// RUN: %clang_cc1 -emit-llvm %s -o -
// PR954

struct _Refcount_Base   {
  unsigned long _M_ref_count;
  int _M_ref_count_lock;
  _Refcount_Base() : _M_ref_count(0) {}
};

struct _Rope_RopeRep : public _Refcount_Base
{
public:
  int _M_tag:8;
};

int foo(_Rope_RopeRep* r) { return r->_M_tag; }