print(ascii(struct.name))
        print(ascii(struct.name.encode("unicode_internal")))
        print(ascii(struct.name.encode("utf-8")))

produces:

'sub-fcc'
b's\x00u\x00b\x00-\x00f\x00c\x00c\x00'
b'sub-fcc'

and that looks correct.

struct.name originally comes from an ini-file:

    cp = configparser.ConfigParser(interpolation=None)
    try:
        cp.read(filename)
    ...

The ini-file is encoded in pure ASCII (while my Python sources are in UTF-8 with the identification bytes at the beginning of the file). struct.name is the name of a section in this file, as provided by cp.sections() . The name gets through several objects. I am not pasting all the relevant code pieces here because there are too many relevant pieces but they do nothing special (just passing and copying the name). I do not use ctypes.

wrkdir is generated from inp_file_name, which is 'default.ini', by this statement:

    wrkdir = os.path.splitext(os.path.abspath(inp_file_name))[0]

BTW, ascii(dirname.encode("unicode_internal")) result is different in this run:

b'D\x00:\x00\\\x00B\x00u\x00g\x00 \x00r\x00e\x00p\x00o\x00r\x00t\x00s\x00\\\x00P\x00y\x00t\x00h\x00o\x00n\x00\\\x00A\x00u\x00t\x00o\x00L\x00E\x00E\x00D\x00\\\x00d\x00e\x00f\x00a\x00u\x00l\x00t\x00\\\x00s\x00u\x00b\x00-\x00f\x00c\x00c\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'