As documented in Doc/extending/newtypes.rst, the flags field of PyMemberDef must be bitwise-or-ed combination of flag constants READONLY, READ_RESTRICTED, WRITE_RESTRICTED and RESTRICTED. There are problems with this:

1. Actually WRITE_RESTRICTED was renamed to PY_WRITE_RESTRICTED in 2.6 (a8dd8874ff2d). I didn't find mention of this backward incompatible change in Misc/NEWS and whatsnew files.

2. Since the support of restricted mode was removed in 3.x, only READONLY flag has effect. Other flags are still documented and used in CPython sources. I think we should get rid of using these flags and undocument them or document as outdated.

3. As noted by Skip Montanaro on the Python-Dev mailing list, these flags (as well as T_* type tags in Include/structmember.h) should have the PY_ prefix.