linux-kernel - Re: [PATCH] Add spaces on either side of case "..." operator.

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Message-ID: <20070410204527.GB5840@martell.zuzino.mipt.ru>
Date:	Wed, 11 Apr 2007 00:45:27 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Robert P. J. Day" <rpjday@...dspring.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add spaces on either side of case "..." operator.

On Tue, Apr 10, 2007 at 10:47:21AM -0700, Jeremy Fitzhardinge wrote:
> Andrew Morton wrote:
> > #define AUDIT_FIRST_USER_MSG    1100    /* Userspace messages mostly uninteresting to kernel */
> > #define AUDIT_USER_AVC          1107    /* We filter this differently */
> > #define AUDIT_LAST_USER_MSG     1199
> >
> > and CPP turns that into
> >
> >  case 1100 ...1199:
> >  case 2100 ...2999:
> >
> > and it does the same when the comments are stripped from the #defines.
> >
> > So we were saved by the trailing space which cpp added to the expanded
> > macro.  I wonder why cpp did that, and to what extent one can rely cpp
> > doing that.
>
> I think its required to.  If it didn't, it would be effectively pasting
> two tokens together without the ## operator.

Internally, there are lists of tokens and no ambiguities. What gcc docs
warn about is that

	case 1...2:

will be parsed as

	case
	[space]
	1.
	.
	.2
	:

which won't fly.

> But putting spaces in is safer - or putting () around the numbers.

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