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From: "Gustavo A. R. Silva" <garsilva@embeddedor.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] x86/syscalls: Mark expected switch fall-throughs
Date: Tue, 28 Nov 2017 12:05:12 -0600	[thread overview]
Message-ID: <20171128120512.Horde.1mz61Up1PsNtyHbrjWmK8L7@gator4166.hostgator.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1711281448520.1723@nanos>


Quoting Thomas Gleixner <tglx@linutronix.de>:

> On Mon, 27 Nov 2017, Gustavo A. R. Silva wrote:
>
>> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
>> where we are expecting to fall through.
>
>>  		case 0:
>>  			if (!n--) break;
>>  			*args++ = regs->bx;
>> +			/* fall through */
>
> And these gazillions of pointless comments help enabling of
> -Wimplicit-fallthrough in which way?
>

The -Wimplicit-fallthrough option was added to GCC 7. We want to add  
that option to the top-level Makefile so we can have the compiler help  
us not make mistakes as missing "break"s or "continue"s. This also  
documents the intention for humans and provides a way for analyzers to  
report issues or ignore False Positives.

So prior to adding such option to the Makefile, we have to properly  
add a code comment wherever the code is intended to fall through.

During the process of placing these comments I have identified actual  
bugs (missing "break"s/"continue"s) in a variety of components in the  
kernel, so I think this effort is valuable. Lastly, such a simple  
comment in the code can save a person plenty of time during a code  
review.

Thanks
--
Gustavo A. R. Silva

  reply	other threads:[~2017-11-28 18:05 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-27 23:52 Gustavo A. R. Silva
2017-11-28 13:49 ` Thomas Gleixner
2017-11-28 18:05   ` Gustavo A. R. Silva [this message]
2017-11-28 18:10     ` Thomas Gleixner
2017-11-28 18:17       ` Thomas Gleixner
2017-11-28 18:22         ` Gustavo A. R. Silva
2017-11-28 18:27           ` Thomas Gleixner
2017-11-28 18:35             ` Thomas Gleixner
2017-11-28 18:45               ` Thomas Gleixner
2017-11-28 18:53                 ` Gustavo A. R. Silva
2017-11-28 19:48                   ` Thomas Gleixner
2017-11-28 19:00               ` Alan Cox
2017-11-28 19:10                 ` Linus Torvalds
2017-11-28 19:59                   ` Joe Perches
2017-11-28 20:08                   ` Thomas Gleixner
2017-11-28 20:34                     ` Kees Cook
2017-11-28 20:37                   ` Gustavo A. R. Silva
2017-11-29  1:07                     ` Joe Perches
2017-11-29  8:20                       ` Geert Uytterhoeven
2017-11-28 20:11                 ` Thomas Gleixner
2017-11-28 20:25                   ` Gustavo A. R. Silva
2017-11-28 21:25                     ` Thomas Gleixner
2017-11-29 15:10                       ` Gustavo A. R. Silva
2017-11-29 15:14                         ` Thomas Gleixner
2017-11-30  0:21                           ` Kees Cook
2019-01-29 23:56 Gustavo A. R. Silva
2019-01-30  0:14 ` Thomas Gleixner

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