linux-kernel - Re: hlist_for_each_entry && pos (Was: task_work

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Message-ID: <20120412050245.GM6589@ZenIV.linux.org.uk>
Date:	Thu, 12 Apr 2012 06:02:45 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	David Smith <dsmith@...hat.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Larry Woodman <lwoodman@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: hlist_for_each_entry && pos (Was: task_work_queue)

On Wed, Apr 11, 2012 at 09:39:29PM -0700, Linus Torvalds wrote:

> The sad part is that if we allow that, we also get that *other* insane
> C99 variable thing - mixing variables and code.
> 
> I *like* getting warnings for confused people who start introducing
> variables in the middle of blocks of code. That's not well-contained
> like the loop variable.
> 
> That said, most of the stuff in C99 are extensions that we used long
> before C99, so I guess we might as well just add the stupid flag. And
> discourage people from mixing declarations and code other ways (sparse
> etc).

	Yes, but... -std=gnu99 will break one of your pet extensions -
(struct foo){0,1,2} will cease to be accepted in initializers of
static storage duration objects (and -std=c99 will break a *lot* more
than that).  I wouldn't mind going for that (it's not a terribly large
patch, at least it wasn't about a year ago when I've looked at that),
but IIRC you really insisted on using that one...  It mostly boiled
down to things like
-       .lock           = __SPIN_LOCK_UNLOCKED(init_fs.lock),
+       .lock           = __SPIN_LOCK_INITIALIZER(init_fs.lock),
etc.
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