Python version: 3.5
Tested with VS Studio 2017 in an C-API extension.

When you have a UTF-8 encoded char buffer which is filled with a 0 or empty, and you youse the PyUnicode_FromString() method on this buffer, you will get a PyObject*. The content looks good, but the refence counter looks strange. 

In case of an 0 as char in the buffer, the ob_refcnt Field is set to 100 and in case of an empty buffer, the ob_refcnt Field is set to something around 9xx. 

Example Code: 
      string s1 = u8"";
      string s2 = u8"0";

      PyObject *o1 = PyUnicode_FromString(s1.c_str());
      //o1->ob_refcnt = 9xx
      PyObject *o2 = PyUnicode_FromString(s2.c_str());
      //o2->ob_refcnt = 100

I think the ob_refcnt Field should be 1 in both cases. Or why is the refcnt here so high?

> I think the ob_refcnt Field should be 1 in both cases. Or why is the refcnt here so high?

Python has singletons for short strings: empty string and 1-character latin1 characters (unicode range [U+0000; U+00FF]).

Examples:

>>> sys.getrefcount("")
103
>>> sys.getrefcount("a")
11

It's not a bug, but an optimization to reduce the memory footprint ;-)