[PATCH] kobject: Suppress compiler warning with gcc 3.x

[PATCH] kobject: Suppress compiler warning with gcc 3.x

[Tetsuo Handa]

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@I-love.SAKURA.ne.jp>
---
 include/linux/kobject.h |   20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

--- linux-2.6.35-rc1.orig/include/linux/kobject.h
+++ linux-2.6.35-rc1/include/linux/kobject.h
@@ -16,6 +16,16 @@
 #ifndef _KOBJECT_H_
 #define _KOBJECT_H_
 
+/*
+ * Namespace types which are used to tag kobjects and sysfs entries.
+ * Network namespace will likely be the first.
+ */
+enum kobj_ns_type {
+	KOBJ_NS_TYPE_NONE = 0,
+	KOBJ_NS_TYPE_NET,
+	KOBJ_NS_TYPES
+};
+
 #include <linux/types.h>
 #include <linux/list.h>
 #include <linux/sysfs.h>
@@ -136,16 +146,6 @@ struct kobj_attribute {
 
 extern const struct sysfs_ops kobj_sysfs_ops;
 
-/*
- * Namespace types which are used to tag kobjects and sysfs entries.
- * Network namespace will likely be the first.
- */
-enum kobj_ns_type {
-	KOBJ_NS_TYPE_NONE = 0,
-	KOBJ_NS_TYPE_NET,
-	KOBJ_NS_TYPES
-};
-
 struct sock;
 
 /*

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

[Eric Dumazet]

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@I-love.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 ?


> ---
>  include/linux/kobject.h |   20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> --- linux-2.6.35-rc1.orig/include/linux/kobject.h
> +++ linux-2.6.35-rc1/include/linux/kobject.h
> @@ -16,6 +16,16 @@
>  #ifndef _KOBJECT_H_
>  #define _KOBJECT_H_
>  
> +/*
> + * Namespace types which are used to tag kobjects and sysfs entries.
> + * Network namespace will likely be the first.
> + */
> +enum kobj_ns_type {
> +	KOBJ_NS_TYPE_NONE = 0,
> +	KOBJ_NS_TYPE_NET,
> +	KOBJ_NS_TYPES
> +};
> +
>  #include <linux/types.h>
>  #include <linux/list.h>
>  #include <linux/sysfs.h>
> @@ -136,16 +146,6 @@ struct kobj_attribute {
>  
>  extern const struct sysfs_ops kobj_sysfs_ops;
>  
> -/*
> - * Namespace types which are used to tag kobjects and sysfs entries.
> - * Network namespace will likely be the first.
> - */
> -enum kobj_ns_type {
> -	KOBJ_NS_TYPE_NONE = 0,
> -	KOBJ_NS_TYPE_NET,
> -	KOBJ_NS_TYPES
> -};
> -
>  struct sock;
>  
>  /*

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

[Américo Wang]

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@I-love.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.

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

[Eric W. Biederman]

Américo Wang <xiyou.wangcong@gmail.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@I-love.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.


Eric

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

[Américo Wang]

On Wed, Jun 02, 2010 at 11:02:28PM -0700, Eric W. Biederman wrote:
>Américo Wang <xiyou.wangcong@gmail.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@I-love.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.

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

[Eric W. Biederman]

Américo Wang <xiyou.wangcong@gmail.com> writes:

> On Wed, Jun 02, 2010 at 11:02:28PM -0700, Eric W. Biederman wrote:
>>Américo Wang <xiyou.wangcong@gmail.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@I-love.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.

You are right gcc 3.x seems full of it.  I was thinking of the !CONFIG_SYSFS
case where I had to pull out the enum because it is in fact inlined.

If we are going to worry about gcc 3.x and about my !CONFIG_SYSFS
inline function the clean way to handle this seems to be to introduce
a new header file that both sysfs.h and kobject.h can include.
Assuming/requiring that files that include sysfs.h also include
kobject.h to seems like the wrong way to go.

Eric

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

[Eric Dumazet]

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@gmail.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@I-love.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
#

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

[Américo Wang]

On Thu, Jun 03, 2010 at 08:46:27AM +0200, Eric Dumazet wrote:
>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@gmail.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@I-love.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

This sounds like a bug of gcc 3.x, gcc 4.x would complain about it.

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

[Américo Wang]

On Wed, Jun 02, 2010 at 11:40:12PM -0700, Eric W. Biederman wrote:
>Américo Wang <xiyou.wangcong@gmail.com> writes:
>
>> On Wed, Jun 02, 2010 at 11:02:28PM -0700, Eric W. Biederman wrote:
>>>Américo Wang <xiyou.wangcong@gmail.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@I-love.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.
>
>You are right gcc 3.x seems full of it.  I was thinking of the !CONFIG_SYSFS
>case where I had to pull out the enum because it is in fact inlined.
>
>If we are going to worry about gcc 3.x and about my !CONFIG_SYSFS
>inline function the clean way to handle this seems to be to introduce
>a new header file that both sysfs.h and kobject.h can include.

Agreed.

>Assuming/requiring that files that include sysfs.h also include
>kobject.h to seems like the wrong way to go.


Yeah.

However, this compile warning only appears in gcc 3.x
and it seems it's a fault of gcc 3.x, not the code. I am wondering
if we need to fix it.

Thanks.

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

[Eric Dumazet]

Le jeudi 03 juin 2010 à 16:57 +0800, Américo Wang a écrit :

> 
> Yeah.
> 
> However, this compile warning only appears in gcc 3.x
> and it seems it's a fault of gcc 3.x, not the code. I am wondering
> if we need to fix it.
> 

I believe gcc-3 was born before the code you mention.

We can keep ability to compile kernel on old gcc for very litle care.

Lets do it please, unless there is a real show-stopper, not because
we feel gcc-3 is 'old'