[PATCH linux-next] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[PATCH linux-next] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[Tim Gardner]

drivers/md/dm-raid.c: In function 'raid_ctr':
drivers/md/dm-raid.c:453:53: warning: 'rebuilds_per_group' may be used uninitialized in this function [-Wuninitialized]
drivers/md/dm-raid.c:383:11: note: 'rebuilds_per_group' was declared here

It appears unlikely that rebuilds_per_group could be used before set, but set
it to 0 anyways just to shutup GCC.

Cc: Alasdair Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Cc: Neil Brown <neilb@suse.de>
Cc: linux-raid@vger.kernel.org
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
 drivers/md/dm-raid.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 9d6bf19..8005caf 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -380,7 +380,7 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
 static int validate_raid_redundancy(struct raid_set *rs)
 {
 	unsigned i, rebuild_cnt = 0;
-	unsigned rebuilds_per_group, copies, d;
+	unsigned rebuilds_per_group = 0, copies, d;
 	unsigned group_size, last_group_start;
 
 	for (i = 0; i < rs->md.raid_disks; i++)
-- 
1.7.9.5

Re: [PATCH linux-next] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[Paul Menzel]

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Dear Tim,


thanks for the patch.


Am Mittwoch, den 20.02.2013, 13:31 -0700 schrieb Tim Gardner:

Noting the `gcc` version and build environment is never wrong. ;-)

> drivers/md/dm-raid.c: In function 'raid_ctr':
> drivers/md/dm-raid.c:453:53: warning: 'rebuilds_per_group' may be used uninitialized in this function [-Wuninitialized]
> drivers/md/dm-raid.c:383:11: note: 'rebuilds_per_group' was declared here
> 
> It appears unlikely that rebuilds_per_group could be used before set,

Why? Otherwise the compiler would not complain, right?

> but set it to 0 anyways just to shutup GCC.

Unfortunately I do not know what linux-next version you tested, so the
line numbers are off in.

        $ git describe
        v3.7.5-4-g9c2ab66

> Cc: Alasdair Kergon <agk@redhat.com>
> Cc: dm-devel@redhat.com
> Cc: Neil Brown <neilb@suse.de>
> Cc: linux-raid@vger.kernel.org
> Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
> ---
>  drivers/md/dm-raid.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> index 9d6bf19..8005caf 100644
> --- a/drivers/md/dm-raid.c
> +++ b/drivers/md/dm-raid.c
> @@ -380,7 +380,7 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
>  static int validate_raid_redundancy(struct raid_set *rs)
>  {
>  	unsigned i, rebuild_cnt = 0;
> -	unsigned rebuilds_per_group, copies, d;
> +	unsigned rebuilds_per_group = 0, copies, d;
>  	unsigned group_size, last_group_start;
>  
>  	for (i = 0; i < rs->md.raid_disks; i++)


Thanks,

Paul

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Re: [PATCH linux-next] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[Paul Menzel]

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Dear Tim,


Am Mittwoch, den 20.02.2013, 23:16 +0100 schrieb Paul Menzel:

> Am Mittwoch, den 20.02.2013, 13:31 -0700 schrieb Tim Gardner:
> 
> Noting the `gcc` version and build environment is never wrong. ;-)
> 
> > drivers/md/dm-raid.c: In function 'raid_ctr':
> > drivers/md/dm-raid.c:453:53: warning: 'rebuilds_per_group' may be used uninitialized in this function [-Wuninitialized]
> > drivers/md/dm-raid.c:383:11: note: 'rebuilds_per_group' was declared here
> > 
> > It appears unlikely that rebuilds_per_group could be used before set,
> 
> Why? Otherwise the compiler would not complain, right?
> 
> > but set it to 0 anyways just to shutup GCC.
> 
> Unfortunately I do not know what linux-next version you tested, so the
> line numbers are off in.
> 
>         $ git describe
>         v3.7.5-4-g9c2ab66

See below …

> > Cc: Alasdair Kergon <agk@redhat.com>
> > Cc: dm-devel@redhat.com
> > Cc: Neil Brown <neilb@suse.de>
> > Cc: linux-raid@vger.kernel.org
> > Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
> > ---
> >  drivers/md/dm-raid.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> > index 9d6bf19..8005caf 100644

Git to the rescue. I guess I should be able to find that commit to make
sense of the line numbers.

> > --- a/drivers/md/dm-raid.c
> > +++ b/drivers/md/dm-raid.c
> > @@ -380,7 +380,7 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
> >  static int validate_raid_redundancy(struct raid_set *rs)
> >  {
> >  	unsigned i, rebuild_cnt = 0;
> > -	unsigned rebuilds_per_group, copies, d;
> > +	unsigned rebuilds_per_group = 0, copies, d;
> >  	unsigned group_size, last_group_start;
> >  
> >  	for (i = 0; i < rs->md.raid_disks; i++)


Thanks,

Paul

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Re: [PATCH linux-next] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[NeilBrown]

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On Wed, 20 Feb 2013 23:16:37 +0100 Paul Menzel <pm.debian@googlemail.com>
wrote:

> Dear Tim,
> 
> 
> thanks for the patch.
> 
> 
> Am Mittwoch, den 20.02.2013, 13:31 -0700 schrieb Tim Gardner:
> 
> Noting the `gcc` version and build environment is never wrong. ;-)
> 
> > drivers/md/dm-raid.c: In function 'raid_ctr':
> > drivers/md/dm-raid.c:453:53: warning: 'rebuilds_per_group' may be used uninitialized in this function [-Wuninitialized]
> > drivers/md/dm-raid.c:383:11: note: 'rebuilds_per_group' was declared here
> > 
> > It appears unlikely that rebuilds_per_group could be used before set,
> 
> Why? Otherwise the compiler would not complain, right?

It is not simply unlikely, it is impossible.  But gcc isn't that clever yet.

> > --- a/drivers/md/dm-raid.c
> > +++ b/drivers/md/dm-raid.c
> > @@ -380,7 +380,7 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
> >  static int validate_raid_redundancy(struct raid_set *rs)
> >  {
> >  	unsigned i, rebuild_cnt = 0;
> > -	unsigned rebuilds_per_group, copies, d;
> > +	unsigned rebuilds_per_group = 0, copies, d;

This should either be:
        unsigned uninitialized_var(rebuilds_per_group);
        unsigned copies, d;

which the old way and is being deprecated, but at least is consistent with
the kernel as it is, or

        unsigned rebuilds_per_group = 0 /* GCC */;
	unsigned copies,d;

which is apparently the new way which I believe is due to be imposed on the
kernel immediately after 3.9-rc1
   https://lwn.net/Articles/529954/

NeilBrown


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Re: [dm-devel] [PATCH linux-next] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[Alasdair G Kergon]

On Wed, Feb 20, 2013 at 01:31:18PM -0700, Tim Gardner wrote:
> drivers/md/dm-raid.c: In function 'raid_ctr':
> drivers/md/dm-raid.c:453:53: warning: 'rebuilds_per_group' may be used uninitialized in this function [-Wuninitialized]
> drivers/md/dm-raid.c:383:11: note: 'rebuilds_per_group' was declared here
 
> It appears unlikely that rebuilds_per_group could be used before set, but set
> it to 0 anyways just to shutup GCC.

Looks bogus to me.
uninitialized_var() please.

Alasdair

[PATCH linux-next v2] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[Tim Gardner]

drivers/md/dm-raid.c:453:53: warning: 'rebuilds_per_group' may be used uninitialized in this function [-Wuninitialized]
drivers/md/dm-raid.c:383:11: note: 'rebuilds_per_group' was declared here

It is impossible that rebuilds_per_group could be used before set, but set
it to 0 anyways to silence GCC warnings.

Cc: Alasdair Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Cc: Neil Brown <neilb@suse.de>
Cc: linux-raid@vger.kernel.org
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---

v2 - Added GCC comment. Update commit log with a more definite explanation.

As Neil has pointed out, https://lwn.net/Articles/529954/ indicates
uninitialized_var() is going away.

 drivers/md/dm-raid.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 9d6bf19..1dbc341 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -380,7 +380,8 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
 static int validate_raid_redundancy(struct raid_set *rs)
 {
 	unsigned i, rebuild_cnt = 0;
-	unsigned rebuilds_per_group, copies, d;
+	unsigned rebuilds_per_group = 0; /* GCC 4.6.3 */
+	unsigned copies, d;
 	unsigned group_size, last_group_start;
 
 	for (i = 0; i < rs->md.raid_disks; i++)
-- 
1.7.9.5

Re: [PATCH linux-next v2] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[Tommi Rantala]

2013/2/21 Tim Gardner <tim.gardner@canonical.com>:
> drivers/md/dm-raid.c:453:53: warning: 'rebuilds_per_group' may be used uninitialized in this function [-Wuninitialized]
> drivers/md/dm-raid.c:383:11: note: 'rebuilds_per_group' was declared here

Hello, is this patch getting merged? I'm also seeing this exact same
compiler warning in my mainline builds.

Tommi

>
> It is impossible that rebuilds_per_group could be used before set, but set
> it to 0 anyways to silence GCC warnings.
>
> Cc: Alasdair Kergon <agk@redhat.com>
> Cc: dm-devel@redhat.com
> Cc: Neil Brown <neilb@suse.de>
> Cc: linux-raid@vger.kernel.org
> Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
> ---
>
> v2 - Added GCC comment. Update commit log with a more definite explanation.
>
> As Neil has pointed out, https://lwn.net/Articles/529954/ indicates
> uninitialized_var() is going away.
>
>  drivers/md/dm-raid.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> index 9d6bf19..1dbc341 100644
> --- a/drivers/md/dm-raid.c
> +++ b/drivers/md/dm-raid.c
> @@ -380,7 +380,8 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
>  static int validate_raid_redundancy(struct raid_set *rs)
>  {
>         unsigned i, rebuild_cnt = 0;
> -       unsigned rebuilds_per_group, copies, d;
> +       unsigned rebuilds_per_group = 0; /* GCC 4.6.3 */
> +       unsigned copies, d;
>         unsigned group_size, last_group_start;
>
>         for (i = 0; i < rs->md.raid_disks; i++)
> --
> 1.7.9.5
>
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Re: [PATCH linux-next v2] DM RAID: validate_raid_redundancy: Silence uninitialized variable warning

[Tim Gardner]

On 06/13/2013 09:30 AM, Tommi Rantala wrote:
> 2013/2/21 Tim Gardner <tim.gardner@canonical.com>:
>> drivers/md/dm-raid.c:453:53: warning: 'rebuilds_per_group' may be used uninitialized in this function [-Wuninitialized]
>> drivers/md/dm-raid.c:383:11: note: 'rebuilds_per_group' was declared here
> 
> Hello, is this patch getting merged? I'm also seeing this exact same
> compiler warning in my mainline builds.
> 
> Tommi
> 

Dunno. I haven't hassled anyone because it _is_ just a warning.
-- 
Tim Gardner tim.gardner@canonical.com