From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Dan Nicolaescu <dann@gnu.org>
Cc: 6740@debbugs.gnu.org
Subject: bug#6740: Spurious byte compiler warnings
Date: Tue, 27 Jul 2010 23:40:50 +0200 [thread overview]
Message-ID: <jwvvd80iozu.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <yxqmxtcwu1w.fsf@fencepost.gnu.org> (Dan Nicolaescu's message of "Tue, 27 Jul 2010 16:26:03 -0400")
>> 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.
> If you use (and (featurep 'xemacs) (not (featurep 'cc-fix) ...
> the warning will go away.
It's one of those cases where the warning is the result of a check done
"too late" (i.e. after some optimization), which means the check is not
performed on the code the user sees, but on some massaged version of it.
It's difficult to avoid them, short of removing all "code
improvement" warnings.
Stefan
next prev parent reply other threads:[~2010-07-27 21:40 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
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 [this message]
2020-11-19 4:25 ` Stefan Kangas
2020-11-24 6:40 ` Lars Ingebrigtsen
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