linux-kernel - Re: [PATCH] kobject: Suppress compiler warning with gcc 3.x

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Date:	Thu, 03 Jun 2010 08:46:27 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	ebiederm@...stanetworks.com, randy.dunlap@...cle.com,
	gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kobject: Suppress compiler warning with gcc 3.x

Le jeudi 03 juin 2010 à 14:23 +0800, Américo Wang a écrit :
> On Wed, Jun 02, 2010 at 11:02:28PM -0700, Eric W. Biederman wrote:
> >Américo Wang <xiyou.wangcong@...il.com> writes:
> >
> >> On Thu, Jun 03, 2010 at 07:31:41AM +0200, Eric Dumazet wrote:
> >>>Le jeudi 03 juin 2010 à 14:23 +0900, Tetsuo Handa a écrit :
> >>>> Gcc 3.x generates a warning
> >>>> 
> >>>>   include/linux/sysfs.h:183: warning: parameter has incomplete type
> >>>> 
> >>>> on each file.
> >>>> Suppress the warning by moving the definition of "enum kobj_ns_type"
> >>>> to before "#include <linux/sysfs.h>".
> >>>> 
> >>>> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> >>>
> >>>
> >>>I was about to submit same patch, but I was also reverting 27eabc7cb4b3
> >>>(sysfs: Don't use enums in inline function declaration.)
> >>>
> >>>So that sysfs_exit_ns() prototype is consistent regardless of
> >>>CONFIG_SYSFS
> >>>
> >>>What do you think ?
> >>>
> >>
> >> This looks odd, in sysfs.h we do have a forward declaration of
> >> enum kobj_ns_type... I am wondering why gcc 3.x doesn't recognize it.
> >
> >Because the replacement is an inline, and we are passing the enum by value
> >gcc wants to see the full definition, at the point where the inline function
> >is declared.
> >
> 
> But sysfs_exit_ns() is not inlined if CONFIG_SYSFS here.
> 

 
# gcc -v
Reading specs from /usr/lib/gcc/i386-redhat-linux/3.4.6/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--disable-checking --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-java-awt=gtk
--host=i386-redhat-linux
Thread model: posix
gcc version 3.4.6 20060404 (Red Hat 3.4.6-10)


# cat try.c
enum kobj_ns_type;
void sysfs_exit_ns(enum kobj_ns_type type, const void *tag);
int main(int argc, char *argv[])
{
	return 0;
}
# gcc -O2 -Wall -o try try.c
try.c:2: warning: parameter has incomplete type
#


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