Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ai.mit.edu!roland
From: roland@ai.mit.edu (Roland McGrath)
Newsgroups: gnu.emacs.bug
Subject: regexp bug
Message-ID: <8907311141.AA02978@apple-gunkies.ai.mit.edu>
Date: 31 Jul 89 11:41:36 GMT
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: GNUs Not Usenet
Lines: 6

I discovered this bug using query-replace-regexp, but it is
undoubtedly in the low-level regexp code.

If the replacement for a \n is empty, for example, with:
(query-replace-regexp "\\(foo\)?" "\\1 bar" nil t)
Then the \1 becomes 1, instead of nothing.