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From: "t.artem at mailcity dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug preprocessor/66322] New: Linus Torvalds: -Wswitch-bool produces dubious warnings, fails to notice really bad things Date: Thu, 28 May 2015 06:51:00 -0000 [thread overview] Message-ID: <bug-66322-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66322 Bug ID: 66322 Summary: Linus Torvalds: -Wswitch-bool produces dubious warnings, fails to notice really bad things Product: gcc Version: 5.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: preprocessor Assignee: unassigned at gcc dot gnu.org Reporter: t.artem at mailcity dot com Target Milestone: --- From: https://lkml.org/lkml/2015/5/27/941 Btw, I'd actually like to see (possibly optionally) a warning for enum types there too. Exactly because *type* based warnings very much make sense, regardless of number of cases. For example, try this: #include <stdbool.h> #include <stdio.h> enum a { one, two }; int t(bool b, enum a e) { switch (b) { case true: printf("No arguments\n"); /* fallthrough */ case false: printf("\n"); } switch (e) { case 0: printf("one"); break; case two: printf("two"); break; } return 0; } and I'd argue that gcc-5.1 warns about TOTALLY THE WRONG THING. It does that *stupid* warning: warning: switch condition has boolean value [-Wswitch-bool] which is just idiotic and wrong. The case statements are clearly boolean, there is absolutely nothing wrong with that switch, and a compiler that warns about it is just being f*cking moronic. In contrast, that second switch() statement with the "case 0:" is actually something that might well be worth warning for. I'd argue that the code would clearly be more legible if it used "case one:" instead. So the new warning in gcc-5 seems to be just stupid. In general, warnings that encourage you to write bad code are stupid. The above switch (boolean) { case true: is *good* code, while the gcc documentation suggests that you should cast it to "int" in order to avoid the warning, but anybody who actually thinks that switch ((int)boolean) { switch 1: is better, clearly has absolutely zero taste and is just objectively wrong. Really. A warning where the very *documentation* tells you to do stupid things is stupid.
next reply other threads:[~2015-05-28 6:51 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-05-28 6:51 t.artem at mailcity dot com [this message] 2015-05-28 8:14 ` [Bug c/66322] " manu at gcc dot gnu.org 2015-05-28 9:29 ` mpolacek at gcc dot gnu.org 2015-05-28 9:38 ` mpolacek at gcc dot gnu.org 2015-05-28 10:31 ` nszabolcs at gmail dot com 2015-05-28 11:37 ` manu at gcc dot gnu.org 2015-06-22 18:16 ` mpolacek at gcc dot gnu.org 2015-06-29 13:13 ` mpolacek at gcc dot gnu.org 2015-10-22 9:14 ` mpolacek at gcc dot gnu.org 2022-01-11 21:00 ` pinskia at gcc dot gnu.org
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