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Re: use of (defvar <foo>)
From: |
Dave Love |
Subject: |
Re: use of (defvar <foo>) |
Date: |
Sun, 09 Apr 2006 14:56:23 +0100 |
User-agent: |
Gnus/5.11 (Gnus v5.11) |
Stefan Monnier <address@hidden> writes:
>>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).
Huh? You don't want it compiled -- that's the point. You're actually
considering changing what eval-when-compile does and breaking more
existing code?? Anyway, the point is that Gnus is supposed to be
supporting Emacs 21 (and XEmacs), the eval-when-compile DTRT
everywhere, and Emacs 22 looks rather a forlorn hope. The
compatibility stuff is typically ugly, but this idiom isn't.
> 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.
That's the point. Without the wrapper it prevents you using the
load-history mechanisms reliably (as I was trying to do to contribute
to Gnus).
> 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).
Actually, such usage was fixed widely in Emacs 21 because it caused
trouble -- try to test a change by unloading a feature and render your
session unusable.
- Re: use of (defvar <foo>), Reiner Steib, 2006/04/07
- Re: use of (defvar <foo>), Stefan Monnier, 2006/04/07
- Re: use of (defvar <foo>), Bill Wohler, 2006/04/07
- Re: use of (defvar <foo>),
Dave Love <=
- Re: use of (defvar <foo>), Stefan Monnier, 2006/04/09
- Re: use of (defvar <foo>), Dave Love, 2006/04/11
- Re: use of (defvar <foo>), David Kastrup, 2006/04/11
- Re: use of (defvar <foo>), Dave Love, 2006/04/13
- Re: use of (defvar <foo>), Stefan Monnier, 2006/04/11
- Re: use of (defvar <foo>), Dave Love, 2006/04/13
Re: use of (defvar <foo>), Richard Stallman, 2006/04/08