Hmmm... the CVS log for Modules/readline.c makes mention of changes made to assure backward compatibility with readline 2.1 and 2.0, and #ifdefs some items as a result. I suppose I could wrap a clear_history in the same.
That's always better, of course. How old were those log entries?
Last December there's a checkin by you of a patch from Magnus Lie Hetland to support 2.0/2.1, on the Python 2.3 branch. More recently, this support was backported to the Python 2.2 maintenance branch, and released in 2.2.3. In each case, the change revolves around an #ifdef for HAVE_RL_COMPLETION_APPEND_CHARACTER, so presumably I can use the same #ifdef to protect clear_history(). (Unless it's preferred to have a distinct flag for this, but I have zero autoconf knowledge/experience, so I might have to ask someone for help on that part.)
Nah, it looks like those featuers were introduced in the same GNU readline release, so it's okay to test for the same symbol.
--Guido van Rossum (home page: http://www.python.org/%7Eguido/)