Re: cc-vars.el

[storm@cua.dk (Kim F. Storm)]

"Stefan Monnier" <monnier+gnu/emacs@rum.cs.yale.edu> writes:

> > > But I also completely agree that we should try to make sure that pragmas
> > > as needed as rarely as possible, so I wholeheartedly support Dave's
> > > suggestion which will at least reduce the amount of useless warnings.
> > 
> > One of the problems I've seen is with code which is conditioned to
> > differentiate between either gnu emacs and xemacs, or between different
> > os-types.
> 
> This is irrelevant: Dave's patch doesn't impact those cases at all.

Off-topic, but not irrelevant IMO.

> 
> > In the first case, many packages seem to have their own "xyz-xemacs-p"
> > function or variable, and the bytecompiler will surely have a hard time
> > determining whether a piece of code isn't used at all on this platform.
> 
> And it shouldn't: the code should simply be fixed.  In 90% of the
> time an fboundp check would be better (and Dave's patch would then have
> a chance of understanding what's going on).

True, but an fboundp check doesn't work in the cases where emacs and xemacs
functions have different parameter lists, such as display-completion-list.

> 
> > A new built-in variable `emacs-type' (value = 'gnu-emacs or e.g. 'xemacs)
> > would fix this problem; for portability, packages may add the following
> > snippet to support older versions of gnu and xemacs:
> 
> We don't want to encourage people to use brain dead tests like those.
> There's already (featurep 'xemacs) for such things.

That's good to know, thanks!!!

A quick scan shows that the following packages don't use the proper test:

        bookmark.el, ediff.el, filesets.el, follow.el, ido.el,
        iswitchb.el, ps-print.el, speedbar.el [partially], term.el,
        type-break.el, edt, viper, eshell, net/eudc-bob.el, ada-mode.el,
        cperl-mode.el, hideshow.el, octave-mod.el, flyspell.el, ispell.el

Even loaddefs.el has (defconst xemacsp ...) which comes from ispell.el

So the tests may be brain dead, but very popular...

> Maybe we should add to byte-opt.el the following snippet:
> 
>    (put 'featurep 'byte-optimizer 'byte-optimize-featurep)
>    (defun byte-optimize-featurep (form)
>      (if (equal '(featurep 'xemacs) form) nil form))
> 
> since Emacs-21's byte-code won't work on XEmacs anyway, there's no
> point keeping XEmacs code around.  It makes the code shorter and
> gets rid of a few warnings.

That's the right approach, yes.  Please install it!

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