Re: Error with add-function and process-filter

[Stefan Monnier via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

> (add-function :before (process-filter h-proc) #'h/trace)
[...]
> However, am getting this error:
> Symbol’s value as variable is void: v

My crystal ball tells me you forgot to activate `lexical-binding`
because you didn't see the message that must have been emitted at some
point:

    Warning: Use of gv-ref probably requires lexical-binding

If you're using a new enough Emacs you can click on the orange "/d" in
your mode line to fix the problem.


        Stefan