From: Alan Mackenzie <acm@muc.de>
To: Chong Yidong <cyd@stupidchicken.com>
Cc: emacs-devel@gnu.org
Subject: Re: Nonsensical byte compiler warning.
Date: 1 Apr 2007 22:57:03 +0200 [thread overview]
Message-ID: <20070401221550.GB1063@muc.de> (raw)
In-Reply-To: <87lkhcj791.fsf@stupidchicken.com>
Hi Chong and David!
On Sun, Apr 01, 2007 at 02:10:18PM -0400, Chong Yidong wrote:
> David Kastrup <dak@gnu.org> writes:
> > when compiling the latest source (with "make cvs-update" in the lisp
> > subdirectory), I get
> > Compiling /home/tmp/emacs/lisp/progmodes/cc-cmds.el...
> > In c-end-of-defun:
> > progmodes/cc-cmds.el:1612:4:Warning: value returned by `char-after' is not
> > used
> > Wrote /home/tmp/emacs/lisp/progmodes/cc-cmds.elc
> > I have no idea where this compiler warning is supposed to come from.
> I don't know why the byte-compiler printed this confusing message, but
> it seems to be issuing a real warning. There is a `when' statement at
> cc-cmds.el:1633 that has no effect, because the return value of the
> surrounding `if' form is discarded.
Yes. There's something stupid about the code there - it looks as though
I've half deleted something at some stage. I'll sort it out early this
week, sometime. (Other things are of higher priority at the moment.)
> This is probably just a bit of cruft, and easily corrected
> (eliminating the warning in the process). Alan, could you verify
> this?
No, this is a long standing problem with cc-cmds.el. I first tried to
track it down (compiled with Emacs 21) in April 2006, but didn't succeed,
beyond identifying the line which I needed to comment out to get rid of
the warning. The line was "(eq (char-before) ?\})" and was at the time
in `c-end-of-defun' (which has since been radically changed). That line
is now L1635; commenting it out silences the warning.
The bug never seemed important enough to lose a lot of sleep over, but it
does irritate. The (more detailed) warning message reported by Emacs 21
is:
While compiling toplevel forms:
** `(char-after (1- (point)))' called for effect
Seemingly, `char-before' is implemented as a macro in the byte-compiler
in Emacs 21.
I strongly believe that cc-cmds.el gets compiled correctly, and that the
spurious warning is a bug in the byte compiler, triggered by something
unusual in cc-cmds.el.
Chong, could you ask the byte-compiler hacker to look at this, please?
(I don't know who that is).
> *** emacs/lisp/progmodes/cc-cmds.el.~1.55.~ 2007-03-30 18:31:07.000000000 -0400
> --- emacs/lisp/progmodes/cc-cmds.el 2007-04-01 14:05:04.000000000 -0400
> ***************
> *** 1630,1639 ****
> (setq arg (1+ arg)))
> (if (< arg 0)
> (setq arg (c-backward-to-nth-BOF-{ (- arg) where)))
> ! (when (and (= arg 0)
> ! (c-syntactic-skip-backward "^}")
> ! (eq (char-before) ?\}))
> ! t))
> ;; Move forward to the } of a function
> (if (> arg 0)
> --- 1630,1637 ----
> (setq arg (1+ arg)))
> (if (< arg 0)
> (setq arg (c-backward-to-nth-BOF-{ (- arg) where)))
> ! (if (= arg 0)
> ! (c-syntactic-skip-backward "^}")))
> ;; Move forward to the } of a function
> (if (> arg 0)
--
Alan.
next prev parent reply other threads:[~2007-04-01 20:57 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-04-01 17:14 Nonsensical byte compiler warning David Kastrup
2007-04-01 18:10 ` Chong Yidong
2007-04-01 20:57 ` Alan Mackenzie [this message]
2007-04-02 12:29 ` Richard Stallman
2007-04-04 4:48 ` Markus Triska
2007-04-04 6:15 ` David Kastrup
2007-04-04 8:19 ` Markus Triska
2007-04-04 8:46 ` David Kastrup
2007-04-04 9:50 ` Markus Triska
2007-04-04 10:17 ` David Kastrup
2007-04-04 12:35 ` Markus Triska
2007-04-04 18:25 ` Markus Triska
2007-04-04 22:13 ` David Kastrup
2007-04-05 6:52 ` Richard Stallman
2007-04-05 7:55 ` Markus Triska
2007-04-06 12:56 ` Richard Stallman
2007-04-06 15:11 ` Chong Yidong
2007-04-08 20:47 ` Markus Triska
2007-04-09 15:42 ` Richard Stallman
2007-04-10 3:53 ` Glenn Morris
2007-04-10 17:27 ` Markus Triska
2007-04-11 4:00 ` Glenn Morris
2007-04-05 18:01 ` Chong Yidong
2007-04-04 20:08 ` Alan Mackenzie
2007-04-04 21:45 ` Markus Triska
2007-04-04 22:11 ` Chong Yidong
2007-04-05 5:44 ` Markus Triska
2007-04-08 1:21 ` Kim F. Storm
2007-04-08 11:27 ` Alan Mackenzie
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