linux-kernel - Re: [PATCH 2/6] ERR_PTR: add ERR_OR_0

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Message-ID: <20080519063355.GA13907@ZenIV.linux.org.uk>
Date:	Mon, 19 May 2008 07:33:55 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Christoph Hellwig <hch@....de>
Cc:	Marcin Slusarz <marcin.slusarz@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/6] ERR_PTR: add ERR_OR_0_PTR

On Mon, May 19, 2008 at 07:55:04AM +0200, Christoph Hellwig wrote:
> On Mon, May 19, 2008 at 12:01:07AM +0200, Marcin Slusarz wrote:
> > Some codepaths call ERR_PTR with possibly 0 argument, which is not
> > a valid errno and rely on conversion from 0 to NULL pointer.
> > Add ERR_OR_0_PTR function which accepts errnos and 0 as an argument.
> 
> Sorry, no.  ERR_PTR(0) is perfectly valid, you just don't want to return
> the actualy value.  E.g. we have a common idiom of:
> 
> 	some_ptr = ERR_PTR(err);
> 	if (IS_ERR(some_ptr))
> 		goto out_handle_err;
> 
> and obsfucating this with new syntactic sugar is not a good idea.

Um... Could somebody explain WTF is wrong with declaring that ERR_PTR(0)
is NULL?  Sure, if we run into a target where converting non-constant
integer with value zero to void * does not result in null pointer, we'll
need to adjust ERR_PTR().  So.  Fscking.  What?
	a) it's not a lot of adjustment, to start with
	b) any such target will require much more work on porting anyway;
this part will be trivial.
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