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From: Jan Kiszka <jan.kiszka@web.de>
To: Jeff Dike <jdike@addtoit.com>
Cc: Amerigo Wang <xiyou.wangcong@gmail.com>,
	trivial@kernel.org, linux-kernel@vger.kernel.org,
	user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [uml-devel] [PATCH 3/5] uml: Fix warning due to missing task_struct	declaration
Date: Tue, 20 Apr 2010 19:09:15 +0200	[thread overview]
Message-ID: <4BCDDFBB.40805@web.de> (raw)
In-Reply-To: <20100420143016.GB30011@c-98-229-117-200.hsd1.ma.comcast.net>


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Jeff Dike wrote:
> On Tue, Apr 20, 2010 at 06:09:49PM +0800, Amerigo Wang wrote:
>> On Mon, Apr 19, 2010 at 11:53:06PM +0200, Jan Kiszka wrote:
>>> We can't pull in linux/sched.h, so just declare the struct.
>>>
>> Did you meet any build error? If yes, please include it.
> 
> What does this patch fix, aside from being a bit cleaner?

  CC      arch/um/sys-i386/elfcore.o
In file included from /data/linux-2.6/include/linux/elf.h:8,
                 from /data/linux-2.6/arch/um/sys-i386/elfcore.c:2:
/data/linux-2.6/arch/um/sys-i386/asm/elf.h:78: warning: ‘struct task_struct’ declared inside parameter list
/data/linux-2.6/arch/um/sys-i386/asm/elf.h:78: warning: its scope is only this definition or declaration, which is probably not what you want

I guess not many people build against i386 hosts anymore, so this
remained widely unnoticed.

> 
> If it built before, without having a task_struct declaration, I think
> that means that the elf_core_copy_fpregs was never used.  The
> task_struct * in the declaration would become a private task_struct,
> known only to the declaration.  If the implementation or callers have
> the regular task_struct, it will be a different one, and the
> prototypes will conflict due to the different types of the first
> parameter.

This is just a forward declaration (that many arch elf header include),
so no such problem exists.

BTW, to answer the other question in this thread: We have a circular
dependency that prevents including sched.h.

I can add all these information to some v2 of this patch if it is
required to get this merged. Please let me know.

Jan



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WARNING: multiple messages have this Message-ID (diff)
From: Jan Kiszka <jan.kiszka@web.de>
To: Jeff Dike <jdike@addtoit.com>
Cc: Amerigo Wang <xiyou.wangcong@gmail.com>,
	trivial@kernel.org, linux-kernel@vger.kernel.org,
	user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [PATCH 3/5] uml: Fix warning due to missing task_struct	declaration
Date: Tue, 20 Apr 2010 19:09:15 +0200	[thread overview]
Message-ID: <4BCDDFBB.40805@web.de> (raw)
In-Reply-To: <20100420143016.GB30011@c-98-229-117-200.hsd1.ma.comcast.net>

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Jeff Dike wrote:
> On Tue, Apr 20, 2010 at 06:09:49PM +0800, Amerigo Wang wrote:
>> On Mon, Apr 19, 2010 at 11:53:06PM +0200, Jan Kiszka wrote:
>>> We can't pull in linux/sched.h, so just declare the struct.
>>>
>> Did you meet any build error? If yes, please include it.
> 
> What does this patch fix, aside from being a bit cleaner?

  CC      arch/um/sys-i386/elfcore.o
In file included from /data/linux-2.6/include/linux/elf.h:8,
                 from /data/linux-2.6/arch/um/sys-i386/elfcore.c:2:
/data/linux-2.6/arch/um/sys-i386/asm/elf.h:78: warning: ‘struct task_struct’ declared inside parameter list
/data/linux-2.6/arch/um/sys-i386/asm/elf.h:78: warning: its scope is only this definition or declaration, which is probably not what you want

I guess not many people build against i386 hosts anymore, so this
remained widely unnoticed.

> 
> If it built before, without having a task_struct declaration, I think
> that means that the elf_core_copy_fpregs was never used.  The
> task_struct * in the declaration would become a private task_struct,
> known only to the declaration.  If the implementation or callers have
> the regular task_struct, it will be a different one, and the
> prototypes will conflict due to the different types of the first
> parameter.

This is just a forward declaration (that many arch elf header include),
so no such problem exists.

BTW, to answer the other question in this thread: We have a circular
dependency that prevents including sched.h.

I can add all these information to some v2 of this patch if it is
required to get this merged. Please let me know.

Jan



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  reply	other threads:[~2010-04-20 17:09 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-04-19 21:53 [PATCH 0/5] uml: Some trivial cleanups Jan Kiszka
2010-04-19 21:53 ` [PATCH 1/5] uml: Remove unused variable from line driver Jan Kiszka
2010-04-20  8:32   ` Amerigo Wang
2010-04-20 14:31   ` Jiri Kosina
2010-04-19 21:53 ` [uml-devel] [PATCH 2/5] uml: Drop private round_down definition Jan Kiszka
2010-04-19 21:53   ` Jan Kiszka
2010-04-20  8:33   ` Amerigo Wang
2010-04-20 14:25     ` Jeff Dike
2010-04-20 15:49       ` [uml-devel] " Jiri Kosina
2010-04-20 15:49         ` Jiri Kosina
2010-04-20 14:35     ` [uml-devel] " Jiri Kosina
2010-04-20 14:35       ` Jiri Kosina
2010-04-20 16:52       ` [uml-devel] " Jeff Dike
2010-04-20 17:18         ` Jiri Kosina
2010-04-20 17:18           ` Jiri Kosina
2010-04-19 21:53 ` [PATCH 3/5] uml: Fix warning due to missing task_struct declaration Jan Kiszka
2010-04-20 10:09   ` Amerigo Wang
2010-04-20 14:30     ` Jeff Dike
2010-04-20 17:09       ` Jan Kiszka [this message]
2010-04-20 17:09         ` Jan Kiszka
2010-04-20 23:43         ` Jiri Kosina
2010-04-21  6:06         ` [uml-devel] " Amerigo Wang
2010-04-21  6:06           ` Amerigo Wang
2010-04-21  9:38           ` [uml-devel] " Jiri Kosina
2010-04-21  9:38             ` Jiri Kosina
2010-04-21 10:43             ` [uml-devel] " Amerigo Wang
2010-04-21 10:43               ` Amerigo Wang
2010-04-21 10:49               ` Jiri Kosina
2010-04-19 21:53 ` [uml-devel] [PATCH 4/5] uml: i386: Avoid redefinition of NR_syscalls Jan Kiszka
2010-04-19 21:53   ` Jan Kiszka
2010-04-20 10:10   ` Amerigo Wang
2010-04-20 17:14     ` Jan Kiszka
2010-04-21  6:12       ` Amerigo Wang
2010-05-10 21:38         ` Jiri Kosina
2010-04-19 21:53 ` [PATCH 5/5] uml: Clean up asm/system.h Jan Kiszka
2010-04-20 10:14   ` [uml-devel] " Amerigo Wang
2010-04-20 10:14     ` Amerigo Wang
2010-04-20 14:33   ` [uml-devel] " Jiri Kosina
2010-04-20 14:33     ` Jiri Kosina

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