Take the following method as an example:
 Klass* ConstantPool::klass_ref_at(int which, TRAPS) {
  return klass_at(klass_ref_index_at(which), CHECK_NULL);
 }

This will expand into:
 Klass* ConstantPool::klass_ref_at(int which, TRAPS) {
  return klass_at(klass_ref_index_at(which), THREAD);
  if (HAS_PENDING_EXCEPTIONS) {
    return NULL;
  }
  (void)(0);
 }

The if-statement will never be reached.

We have seen cases where the compiler warns about this, and the recent change to enable -Wreturn-type will make this more likely to happen.

The suggested solution is to change the example above into:
 Klass* ConstantPool::klass_ref_at(int which, TRAPS) {
  return klass_at(klass_ref_index_at(which), THREAD);
 }