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From: Finn Thain <fthain@telegraphics.com.au>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>,
	Kees Cook <keescook@chromium.org>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
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	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Greg KH <gregkh@linuxfoundation.org>
Subject: Re: [Intel-wired-lan] [PATCH 000/141] Fix fall-through warnings for Clang
Date: Thu, 26 Nov 2020 10:21:54 +1100 (AEDT)
Message-ID: <alpine.LNX.2.23.453.2011260918510.6@nippy.intranet> (raw)
In-Reply-To: <CAKwvOdna5Zj_O=sB7Q0jHZX0BJSaakX=ZyftwQ_3=L3-ZB54XQ@mail.gmail.com>

On Wed, 25 Nov 2020, Nick Desaulniers wrote:

> On Wed, Nov 25, 2020 at 1:33 PM Finn Thain <fthain@telegraphics.com.au> 
> wrote:
> >
> > Or do you think that a codebase can somehow satisfy multiple checkers 
> > and their divergent interpretations of the language spec?
> 
> Have we found any cases yet that are divergent? I don't think so.

There are many implementations, so I think you are guaranteed to find more 
divergence if you look. That's because the spec is full of language like 
this: "implementations are encouraged not to emit a diagnostic" and 
"implementations are encouraged to issue a diagnostic".

Some implementations will decide to not emit (under the premise that vast 
amounts of existing code would have to get patched until the compiler goes 
quiet) whereas other implementations will decide to emit (under the 
premise that the author is doing the checking and not the janitor or the 
packager).

> It sounds to me like GCC's cases it warns for is a subset of Clang's. 
> Having additional coverage with Clang then should ensure coverage for 
> both.
> 

If that claim were true, the solution would be simple. (It's not.)

For the benefit of projects that enable -Werror and projects that 
nominated gcc as their preferred compiler, clang would simply need a flag 
to enable conformance with gcc by suppressing those additional warnings 
that clang would normally produce.

This simple solution is, of course, completely unworkable, since it would 
force clang to copy some portion of gcc's logic (rewritten under LLVM's 
unique license) and then to track future changes to that portion of gcc 
indefinitely.

  reply index

Thread overview: 70+ 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 18:40 ` [PATCH 134/141] video: fbdev: lxfb_ops: " Gustavo A. R. Silva
2020-11-22 22:05   ` Sam Ravnborg
2020-11-24 14:44     ` Gustavo A. R. Silva
2020-11-20 18:40 ` [PATCH 135/141] video: fbdev: pm2fb: " 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 [this message]
2020-11-26  0:30                                 ` Finn Thain
     [not found]                             ` <20201125082405.1d8c23dc@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
2020-11-25 17:04                               ` Miguel Ojeda
2020-11-25 22:09                               ` Nick Desaulniers
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
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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