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From: Dan Carpenter <dan.carpenter@oracle.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kees Cook <keescook@chromium.org>,
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Subject: Re: [PATCH 000/141] Fix fall-through warnings for Clang
Date: Tue, 1 Dec 2020 17:08:49 +0300
Message-ID: <20201201140849.GH2767@kadam> (raw)
In-Reply-To: <CAKwvOdntVfXj2WRR5n6Kw7BfG7FdKpTeHeh5nPu5AzwVMhOHTg@mail.gmail.com>

On Mon, Nov 23, 2020 at 05:32:51PM -0800, Nick Desaulniers wrote:
> On Sun, Nov 22, 2020 at 8:17 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Fri, Nov 20, 2020 at 11:51:42AM -0800, Jakub Kicinski wrote:
> > > If none of the 140 patches here fix a real bug, and there is no change
> > > to machine code then it sounds to me like a W=2 kind of a warning.
> >
> > FWIW, this series has found at least one bug so far:
> > https://lore.kernel.org/lkml/CAFCwf11izHF=g1mGry1fE5kvFFFrxzhPSM6qKAO8gxSp=Kr_CQ@mail.gmail.com/
> 
> So looks like the bulk of these are:
> switch (x) {
>   case 0:
>     ++x;
>   default:
>     break;
> }

This should not generate a warning.

> 
> I have a patch that fixes those up for clang:
> https://reviews.llvm.org/D91895
> 
> There's 3 other cases that don't quite match between GCC and Clang I
> observe in the kernel:
> switch (x) {
>   case 0:
>     ++x;
>   default:
>     goto y;
> }
> y:;

This should generate a warning.

> 
> switch (x) {
>   case 0:
>     ++x;
>   default:
>     return;
> }

Warn for this.


> 
> switch (x) {
>   case 0:
>     ++x;
>   default:
>     ;
> }

Don't warn for this.

If adding a break statement changes the flow of the code then warn about
potentially missing break statements, but if it doesn't change anything
then don't warn about it.

regards,
dan carpenter

  parent reply index

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-20 18:21 Gustavo A. R. Silva
2020-11-20 18:28 ` Joe Perches
2020-11-20 19:02   ` Gustavo A. R. Silva
2020-11-20 18:32 ` [PATCH 054/141] target: " Gustavo A. R. Silva
2020-11-20 18:53 ` [PATCH 000/141] " Jakub Kicinski
2020-11-20 19:04   ` Gustavo A. R. Silva
2020-11-20 19:30   ` Kees Cook
2020-11-20 19:51     ` Jakub Kicinski
2020-11-20 20:48       ` Kees Cook
2020-11-22 16:17       ` Kees Cook
2020-11-22 18:21         ` James Bottomley
2020-11-22 18:25           ` Joe Perches
2020-11-22 19:12             ` James Bottomley
2020-11-22 19:22               ` Joe Perches
2020-11-22 19:53                 ` James Bottomley
2020-11-23 13:03                   ` [Intel-wired-lan] " Gustavo A. R. Silva
2020-11-23 16:31                     ` James Bottomley
2020-11-24 21:32                       ` Kees Cook
2020-11-24 22:24                         ` Finn Thain
2020-11-24 23:15                           ` Miguel Ojeda
2020-11-24 23:53                             ` Finn Thain
2020-11-25  1:05                               ` Miguel Ojeda
2020-11-25  7:05                         ` James Bottomley
2020-11-25 12:24                           ` Nick Desaulniers
2020-11-25 21:33                             ` Finn Thain
2020-11-25 22:09                               ` Nick Desaulniers
2020-11-25 23:21                                 ` Finn Thain
2020-11-26  0:30                                 ` Finn Thain
2020-11-25 21:10                           ` Kees Cook
2020-11-22 20:35           ` Miguel Ojeda
2020-11-22 22:36             ` James Bottomley
2020-11-23 14:19               ` Miguel Ojeda
2020-11-23 15:58                 ` James Bottomley
2020-11-23 16:24                   ` Rafael J. Wysocki
2020-11-23 16:32                   ` Joe Perches
2020-11-23 18:56                   ` Miguel Ojeda
2020-11-23 20:37                     ` James Bottomley
2020-11-25  0:32                       ` Miguel Ojeda
2020-11-25 22:44                         ` Edward Cree
2020-11-26 14:53                           ` Miguel Ojeda
2020-11-26 15:28                             ` Geert Uytterhoeven
2020-11-26 16:18                               ` Karol Herbst
2020-11-26 17:05                               ` Miguel Ojeda
2020-11-25 10:38                       ` Andy Shevchenko
2020-11-25  9:01                   ` Sean Young
2020-11-22 22:54             ` Finn Thain
2020-11-22 23:04               ` James Bottomley
2020-11-23 14:05               ` Miguel Ojeda
2020-11-24  0:58                 ` Finn Thain
2020-11-24  1:05                   ` Joe Perches
2020-11-24  2:48                     ` Finn Thain
2020-11-24 23:46                   ` Miguel Ojeda
2020-11-22 22:10           ` Sam Ravnborg
2020-11-24  1:32         ` Nick Desaulniers
2020-11-24 21:25           ` Kees Cook
2020-11-25 23:02             ` Edward Cree
2020-12-01 14:08           ` Dan Carpenter [this message]
2020-12-01 14:04         ` Dan Carpenter
2020-11-20 22:21 ` Miguel Ojeda
2020-11-23 20:03 ` Jason Gunthorpe
2020-11-24 14:47   ` Gustavo A. R. Silva
     [not found] ` <160616392671.21180.16517492185091399884.b4-ty@kernel.org>
2020-11-24 14:47   ` Gustavo A. R. Silva
2020-12-01  5:52 ` Martin K. Petersen
2020-12-01  8:20   ` Gustavo A. R. Silva
2020-12-08  4:52 ` (subset) " Martin K. Petersen

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