Can't clear stale match data after failed match

Some time ago you reported a bug that stale match data was being preserved. It turns out that the cases in question involved a match that failed and returned nil. I agree that according to existing documentation code should expect that match data be cleared in this case, but a patch to fix the behvaior resulted in a rash of "wrong-type-argument integerp, nil" errors as `match-beginning' etc started returning nil instead of stale match data. This led me to some very plausible code (cf. the function `w3-configuration-data' in w3/w3-cfg.el) which expects the match data to be preserved. Furthermore, this code cannot use `save-match', and use of `match-data' and `store-match-data' would be extremely clumsy, at best. There appears to be a fair amount of it; there are a number of different bugs being reported that seem to be related to this change. So I'm going to revert the fix at least temporarily. (The fix has not yet been applied to 21.4; this discussion applies only to 21.5 for now.) Did you have a specific use for having the match data cleared? Would you describe it? Is there a practical reason why using `(store-match-data nil)' to clear the match data would be unacceptable? (Aside from the fact that clearing the match data that way looks to be a memory leak :-p, but I will fix that.) Thanks for your help. -- Institute of Policy and Planning Sciences http://turnbull.sk.tsukuba.ac.jp University of Tsukuba Tennodai 1-1-1 Tsukuba 305-8573 JAPAN Ask not how you can "do" free software business; ask what your business can "do for" free software.