Re: [PATCH] Use __unused.0 instead of __unused for user visible struct members

[Justin Cormack <justin at specialbusservice dot com>]

On Wed, Nov 13, 2013 at 4:55 PM, Carlos O'Donell <carlos@redhat.com> wrote:
> On 11/13/2013 06:09 AM, OndÅej BÃlka wrote:
>> On Tue, Nov 12, 2013 at 11:44:58PM -0500, Carlos O'Donell wrote:
>>> On 11/05/2013 08:54 AM, OndÅej BÃlka wrote:
>>>> On Mon, Oct 28, 2013 at 03:41:18PM +0000, Justin Cormack wrote:
>>>>> On Mon, Oct 28, 2013 at 1:30 PM, Joseph S. Myers
>>>>> <joseph@codesourcery.com> wrote:
>>>>>> On Mon, 28 Oct 2013, Justin Cormack wrote:
>>>>>>
>>>>>>> A patch was submitted for this a while back
>>>>>>> https://sourceware.org/ml/libc-alpha/2012-01/msg00001.html and did not
>>>>>>> get a good reception from the maintainer at the time. Attached is an
>>>>>>> updated version for current glibc head.
>>>>>>
>>>>>> I believe we had consensus on use of __glibc_reserved as a prefix in such
>>>>>> cases (allowing for __glibc_reserved0, __glibc_reserved1 or
>>>>>> __glibc_reserved_foo, __glibc_reserved_bar in cases where more than one
>>>>>> identifier, or a more meaningful name, is needed).
>>>>>
>>>>> OK, that makes sense, found part of that conversation in the archives.
>>>>> Here is a patch (inline and attached) to convert all uses to
>>>>> __glibc_reserved.
>>>>>
>>>>> Justin
>>>>>
>>>> A mechanical change that looks ok,
>>>>
>>>> It needs changelog so I generated following.
>>>
>>> Could you please repost with the patch and final ChangeLog,
>>> TO me, CC libc-alpha, and I'll review.
>>>
>>> Cheers,
>>> Carlos.
>>>
>> Here
>
> OK to checkin as long as you do 2 more things please:
>
> 1. Email libc-ports and explain that you've made cross-machine
>    changes and renamed __unused to __glibc_reserved and to look
>    for any unintended breakage.
>
> 2. Update https://sourceware.org/glibc/wiki/Style_and_Conventions
>    and add an entry on this to explain that we use __glibc_reserved
>    for unused structure entries and that this is done to avoid
>    __unused which causes problems with BSD sources.

I have done 1. I don't have permission to edit that wiki page (user
JustinCormack). I suggest something like:

== Unused structure members ==

Structure members that are not used, but inserted for padding,
alignment and future use reasons, should be named '__glibc_reserved'
or numbered with 'glibc_reserved1', 'glibc_reserved2' in the case of
multiple parameters. This form should be used instead of the historic
'__unused' as this conflicts with the use of '__unused' in BSD code.
These structure members should not be used in user code, as they are
subject to change and vary by architecture and are reserved for the
implementation.

Justin