Re: use of (defvar <foo>)

[Bill Wohler <wohler@newt.com>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> Could people on emacs-devel please comment on this?
>> Should we use (defvar <foo>) or (eval-when-compile (defvar <foo>)) in Gnus
>> for compatibility with Emacs 21?  (Probably the same holds for MH-E.)
>
>>From the future's point of view (Emacs-22 and up), placing such defvars
> inside eval-when-compile is a bad practice (in the future it may even fail
> to work since there's nothing that guarantees that the content of
> eval-when-compile is actually compiled rather than just eval'd).
>
> In Emacs-21 and older, such a defvar will have some undesirable minor
> side-effects (via the load-history) unless it is placed inside an
> eval-when-compile *and* the file is byte-compiled.  Indeed placing the
> defvar inside the eval-when-compile has no effect if the file is not
> byte-compiled.
>
> I'd recommend to not use eval-when-compile since that's what many packages
> have been doing for many years without suffering much (if ever) of the
> occasional side-effects (which only affect unload-feature and sometimes
> C-h v).
>
> But it's your call, really.

I was planning on stripping the eval-when-compile defvar wrappers for
the MH-E 8.0/Emacs 22.1 release. Reiner, is the problem you describe
real or theoretical?

-- 
Bill Wohler <wohler@newt.com>  http://www.newt.com/wohler/  GnuPG ID:610BD9AD
Maintainer of comp.mail.mh FAQ and MH-E. Vote Libertarian!
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