linux-kernel - Re: [PATCH] Use __unused0 instead of __unused for user visible struct member names

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Message-ID: <20120104133522.GA7147@merkur.ravnborg.org>
Date:	Wed, 4 Jan 2012 14:35:22 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Michal Marek <mmarek@...e.cz>
Cc:	Guillem Jover <guillem@...rons.org>,
	Jonathan Nieder <jrnieder@...il.com>,
	linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH] Use __unused0 instead of __unused for user visible
	struct member names

On Wed, Jan 04, 2012 at 12:03:16PM +0100, Michal Marek wrote:
> On 4.1.2012 09:14, Guillem Jover wrote:
> > On Tue, 2012-01-03 at 07:56:59 +0100, Sam Ravnborg wrote:
> >> On Mon, Jan 02, 2012 at 02:22:43PM -0600, Jonathan Nieder wrote:
> >>> Guillem Jover wrote:
> >>>> On BSD systems __unused has traditionally been defined to mean the
> >>>> equivalent of gcc's __attribute__((__unused__)), some parts of the
> >>>> Linux tree use that convention too (e.g. perf). The problem comes when
> >>>> defining such macro while trying to build unmodified source code with
> >>>> BSD origins on systems with Linux headers.
> >>>>
> >>>> Rename the user visible struct members from __unused to __unused0 to
> >>>> not cause compilation failures due to that macro, which should not be
> >>>> a problem as those members are supposed to be private anyway.
> >>
> >> ^__ is reserved for libc internal stuff and there is no reason to
> >> name the unused/padding members "__unused".
> >> So one or a set of patches that rename them all to something more
> >> sensible would be fine.
> > 
> > On a quick glance, I've found other functionally similar struct
> > member names present on the tree:
> > 
> >   __unused __unusedN __reserved __reservedN __reserved_N __resN
> >   __pad __padN __flr_pad __ifi_pad __tcpm_padN __tcpct_padN
> > 
> > Do you mean you'd like to see patch(es) to rename all those? I'd not
> > mind providing them, although my immediate concern right now is just
> > regarding __unused.
> 
> __.* and _[A-Z].* are reserved for the implementation. Unfortunately,
> both the kernel userspace headers and the libc are part of the
> implementation, so there needs to be some common sense applied to avoid
> clashes. IMO renaming __unused to __unused0 on the basis that some
> headers define __unused to __attribute__((__unused__)) makes sense, but
> blindly renaming any occurence of double underscore helps little.

Agree on Michael on this.

	Sam
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