From: "Mattias Engdegård" <mattias.engdegard@gmail.com>
To: Michael Heerdegen <michael_heerdegen@web.de>
Cc: 61730@debbugs.gnu.org, Stefan Monnier <monnier@iro.umontreal.ca>
Subject: bug#61730: 30.0.50; Compiler warnings for delq and delete
Date: Fri, 24 Feb 2023 14:43:34 +0100 [thread overview]
Message-ID: <670D8E4A-333D-4E2D-97CC-86728965989D@gmail.com> (raw)
In-Reply-To: <87ilfsisje.fsf@web.de>
> I think we should add compiler warnings
You rang?
> for `delete' and `delq' function
> calls whose return values are unused.
Let's experiment: warning about for-effect calls to
mapcar mapcan mapconcat
delq delete delete-dups delete-consecutive-dups
cl-delete cl-delete-if cl-delete-if-not cl-delete-duplicates
sort
results in 34 such calls found on master, most of them about `delq` and `delete`, but `delete-dups`, `cl-delete`, `mapconcat` and `sort` are also represented.
Some of these are no doubt safe, a few of them knowingly so, but it's definitely not obvious from a quick look at the code. It's poor style in any case.
Thus such a warning definitely falls on the beneficial side. Let's do it.
> I think the warnings could be added in a similar way as the "mapcar
> called for effect" warnings work.
That's probably the best place to start (although we prefer warnings to be emitted by the front-end and not in codegen).
We may want to change the warning text from "called for effect" because it's written from the perspective of the compiler; the programmer thinks of it as 'not using the return value'.
For that matter, `with-suppressed-warnings` doesn't work for suppressing this warning very well; we may want to do something about that. This is true for the existing `mapcar` warning as well.
> Adding the same kind of warning for `remq' and `remove' would probably
> also be useful. This will probably not occur that often but it still
> would be useful I think.
The compiler should already warn about those two since they are declared side-effect-free. Unless somehow `byte-compile-delete-errors` is set during compilation, which can happen if the code messes about with (optimise (safety ...)) -- it's a bit unfortunate. Please tell us if you observe anomalies in this regard.
next prev parent reply other threads:[~2023-02-24 13:43 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-23 10:29 bug#61730: 30.0.50; Compiler warnings for delq and delete Michael Heerdegen
2023-02-24 3:59 ` Richard Stallman
2023-02-24 13:43 ` Mattias Engdegård [this message]
2023-02-24 13:56 ` Eli Zaretskii
2023-02-24 15:11 ` Michael Heerdegen
2023-02-24 15:29 ` Eli Zaretskii
2023-02-24 15:45 ` Michael Heerdegen
2023-02-24 15:48 ` Eli Zaretskii
2023-02-24 16:17 ` Michael Heerdegen
2023-02-24 16:45 ` Michael Heerdegen
2023-02-24 19:33 ` Mattias Engdegård
2023-02-24 20:20 ` Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-02-25 9:40 ` Mattias Engdegård
2023-02-25 4:15 ` Richard Stallman
2023-02-25 8:11 ` Eli Zaretskii
2023-02-25 12:34 ` Michael Heerdegen
2023-02-25 13:25 ` Eli Zaretskii
2023-02-25 15:09 ` Michael Heerdegen
2023-02-25 15:29 ` Michael Heerdegen
2023-02-25 15:48 ` Eli Zaretskii
2023-02-27 3:22 ` Richard Stallman
2023-02-27 10:37 ` Michael Heerdegen
2023-02-27 11:37 ` Eli Zaretskii
2023-02-27 3:24 ` Richard Stallman
2023-02-27 11:44 ` Eli Zaretskii
2023-02-24 15:52 ` Mattias Engdegård
2023-02-24 16:37 ` Michael Heerdegen
2023-04-09 16:41 ` Mattias Engdegård
2023-05-01 16:06 ` Mattias Engdegård
2023-05-20 1:57 ` Michael Heerdegen
2023-05-20 9:14 ` Mattias Engdegård
2023-05-21 0:56 ` Michael Heerdegen
2023-05-21 3:01 ` Ruijie Yu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2023-05-21 3:57 ` Michael Heerdegen
2023-05-21 5:55 ` Eli Zaretskii
2023-05-21 8:42 ` Mattias Engdegård
2023-05-31 14:38 ` Mattias Engdegård
2023-06-01 0:48 ` Michael Heerdegen
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