Emacs occasionally hangs when doing isearch-forward.

[Makarius]

Using GNU emacs 22.1.1 on Ubuntu 7.10, the editor occasionally hangs when doing isearch-forward.

E.g. reproduce this by visiting Isabelle/src/HOL/Lambda/WeakNorm.thy: type C-s, type "c" "o" "n" "s" (which finds an occurreny of "Cons" in the text), continuing to type "t" makes emacs hang; after C-g it works again, but there is some danger it will again hang later.

[David Aspinall]

Can't reproduce with 22.1.1 on Fedora 8, just get immediate search failure.

Presumably this is with X-Symbol enabled, is it reproducible with it off?

Doing

(setq debug-on-quit t)

or

  Options -> Enter Debugger On Quit

May give a useful backtrace with C-g.