Undocumented change in binding of buffer-local variables?

Undocumented change in binding of buffer-local variables?

[Luc Teirlinck]

There used to be (in Emacs20.7 and earlier) a problem with binding a
buffer-local variable with let and then exiting the let form with a
different current buffer.

From experimentation, it would seem that this problem is now totally
solved.  Is this correct?  If so, would it not be worth mentioning
this in the GNU Emacs NEWS?  (Maybe I overlooked something, but
conducting a search for "let" failed to find anything related.)

I found a bug in ielm which I can easily fix and for which I will send
a report and patch soon.  However, the best solution depends on
whether or not it is now safe to exit a let-form, binding buffer-local
variables, with a changed current buffer.

Sincerely,

Luc.

Re: Undocumented change in binding of buffer-local variables?

[Kim F. Storm]

Luc Teirlinck <teirllm@dms.auburn.edu> writes:

> There used to be (in Emacs20.7 and earlier) a problem with binding a
> buffer-local variable with let and then exiting the let form with a
> different current buffer.
> 
> >From experimentation, it would seem that this problem is now totally
> solved.  Is this correct?  If so, would it not be worth mentioning
> this in the GNU Emacs NEWS?  (Maybe I overlooked something, but
> conducting a search for "let" failed to find anything related.)
> 
> I found a bug in ielm which I can easily fix and for which I will send
> a report and patch soon.  However, the best solution depends on
> whether or not it is now safe to exit a let-form, binding buffer-local
> variables, with a changed current buffer.
> 

Please read the updated information in the elisp manual
section "Introduction to Buffer-Local Variables".

The Warning and the example related to buffer-local variables
have been updated.

-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk

Re: Undocumented change in binding of buffer-local variables?

[Stefan Monnier]

> I found a bug in ielm which I can easily fix and for which I will send
> a report and patch soon.  However, the best solution depends on
> whether or not it is now safe to exit a let-form, binding buffer-local
> variables, with a changed current buffer.

Yes, Gerd fixed this long-standing bug.  It's not in NEWS because
it's rather obscure and is considered as a bug-fix, I think.


	Stefan

Re: Undocumented change in binding of buffer-local variables?

[Richard Stallman]

    I found a bug in ielm which I can easily fix and for which I will send
    a report and patch soon.  However, the best solution depends on
    whether or not it is now safe to exit a let-form, binding buffer-local
    variables, with a changed current buffer.

I suggest you play it safe anyway.