netdev - Re: [PATCH] net: sctp: Rename fallthrough label to unhandled

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Date:   Wed, 31 Jul 2019 15:23:46 -0700
From:   Joe Perches <joe@...ches.com>
To:     Neil Horman <nhorman@...driver.com>
Cc:     Vlad Yasevich <vyasevich@...il.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: sctp: Rename fallthrough label to unhandled

On Wed, 2019-07-31 at 16:58 -0400, Neil Horman wrote:
> On Wed, Jul 31, 2019 at 09:35:31AM -0700, Joe Perches wrote:
> > On Wed, 2019-07-31 at 08:16 -0400, Neil Horman wrote:
> > > On Wed, Jul 31, 2019 at 04:32:43AM -0700, Joe Perches wrote:
> > > > On Wed, 2019-07-31 at 07:19 -0400, Neil Horman wrote:
> > > > > On Tue, Jul 30, 2019 at 10:04:37PM -0700, Joe Perches wrote:
> > > > > > fallthrough may become a pseudo reserved keyword so this only use of
> > > > > > fallthrough is better renamed to allow it.
> > > > > > 
> > > > > > Signed-off-by: Joe Perches <joe@...ches.com>
> > > > > Are you referring to the __attribute__((fallthrough)) statement that gcc
> > > > > supports?  If so the compiler should by all rights be able to differentiate
> > > > > between a null statement attribute and a explicit goto and label without the
> > > > > need for renaming here.  Or are you referring to something else?
> > > > 
> > > > Hi.
> > > > 
> > > > I sent after this a patch that adds
> > > > 
> > > > # define fallthrough                    __attribute__((__fallthrough__))
> > > > 
> > > > https://lore.kernel.org/patchwork/patch/1108577/
> > > > 
> > > > So this rename is a prerequisite to adding this #define.
> > > > 
> > > why not just define __fallthrough instead, like we do for all the other
> > > attributes we alias (i.e. __read_mostly, __protected_by, __unused, __exception,
> > > etc)
> > 
> > Because it's not as intelligible when used as a statement.
> I think thats somewhat debatable.  __fallthrough to me looks like an internal
> macro, whereas fallthrough looks like a comment someone forgot to /* */


I'd rather see:

	switch (foo) {
	case FOO:
		bar |= baz;
		fallthrough;
	case BAR:
		bar |= qux;
		break;
	default:
		error();
	}

than

	switch (foo) {
	case FOO:
		bar |= baz;
		__fallthrough;
	case BAR:
		bar |= qux;
		break;
	default:
		error();
	}

or esoecially

	switch (foo) {
	case FOO:
		bar |= baz;
		/* fallthrough
*/;
	case BAR:
		bar |= qux;
		break;
	default:
		error();
	}

but <shrug>, bikeshed ahoy!...