From: Alan Mackenzie <acm@muc.de>
To: Dan Nicolaescu <dann@gnu.org>
Cc: 6740@debbugs.gnu.org
Subject: bug#6740: Spurious byte compiler warnings
Date: Tue, 27 Jul 2010 21:23:28 +0000 [thread overview]
Message-ID: <20100727212328.GD2280@muc.de> (raw)
In-Reply-To: <yxqmxtcwu1w.fsf@fencepost.gnu.org>
Hi, Dan,
On Tue, Jul 27, 2010 at 04:26:03PM -0400, Dan Nicolaescu wrote:
> Alan Mackenzie <acm@muc.de> writes:
> > Hi, Emacs!
> > (i) Start Emacs, even a most recent bzr version, with -Q.
> > (ii) Put the following into the *scratch* buffer:
> > (eval-when-compile
> > (if (and (not (featurep 'cc-fix))
> > (featurep 'xemacs)
> > (progn
> > (require 'font-lock)
> > (let (font-lock-keywords)
> > (font-lock-compile-keywords '("\\<\\>"))
> > font-lock-keywords)))
> > (cc-load "cc-fix")))
> > (This fragment is at the top level, and taken from cc-defs.el.).
> > (iii) do M-x compile-defun on this form.
> > The byte compiler then issues the following two identical error
> > messages:
> > Warning: value returned from (featurep (quote cc-fix)) is unused
> > Warning: value returned from (featurep (quote cc-fix)) is unused
> > It is obvious that that value is indeed used. This is a bug.
> The byte compiler knows that (featurep 'xemacs) is false, so
> (and (not (featurep 'cc-fix)) ... )
> will be false, so the featurep result is indeed unused.
Ah, thanks for the explanation! But .....
It's a bug that the error message is repeated, at the very least. And
the message is most assuredly false because (featurep 'cc-fix) isn't
always false - for example when it's run under XEmacs.
> If you use (and (featurep 'xemacs) (not (featurep 'cc-fix) ...
> the warning will go away.
At the very least, emitting such arcane warnings is unhelpful. Are there
any circumstances in which such a warning might help a hacker improve his
code? Surely we aren't in the business of making it difficult to adapt
code for XEmacs?
I think it's clear, the only code containing (featurep 'xemacs) is
portable code. Can we please remove this unhelpful warning?
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2010-07-27 21:23 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-27 20:06 bug#6740: Spurious byte compiler warnings Alan Mackenzie
2010-07-27 20:26 ` Dan Nicolaescu
2010-07-27 21:23 ` Alan Mackenzie [this message]
2010-07-27 22:57 ` Juanma Barranquero
2010-07-28 17:49 ` Alan Mackenzie
2010-07-28 17:56 ` Juanma Barranquero
2010-07-28 19:45 ` Alan Mackenzie
2010-07-28 19:54 ` Juanma Barranquero
2010-07-28 23:00 ` Dan Nicolaescu
2010-07-29 20:24 ` Alan Mackenzie
2010-07-29 20:36 ` Juanma Barranquero
2010-07-27 21:40 ` Stefan Monnier
2020-11-19 4:25 ` Stefan Kangas
2020-11-24 6:40 ` Lars Ingebrigtsen
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