Re: Multiple M-x shells sharing input ring

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I don't see how anything in that description applies here.  Maybe
> the description is faulty.  Or maybe this variable should not be
> permanent-local.  But so far, the description does not seem (to me)
> to fit the `comint-input-history' case.

permanent-local is used to mark variables as pertaining to the content
of a buffer rather than to its mode.  The effect it has is that the
variable won't be reset if you change major mode (i.e. it's not
"killed" by kill-local-variables).

It's reasonably common in comint buffer to reset the major mode
(typically, you kill the process and re-run it which sets up the comint
mode again) and you generally want to preserve the input-history, hence
the `permanent-local' property.

Note also that the `permanent-local' property does not make a variable
buffer-local.  It just makes it stay local longer, in case it was
made local.


        Stefan