[PATCH iproute2] ip, route: fix minor compile warning

[PATCH iproute2] ip, route: fix minor compile warning

[Daniel Borkmann]

Seems like gcc (4.8.3) doesn't catch this false positive, triggering
after 0f7543322c5f ("route: ignore RTAX_HOPLIMIT of value -1"):

  iproute.c: In function 'print_route':
  iproute.c:301:12: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
     features &= ~RTAX_FEATURE_ECN;
              ^
  iproute.c:575:10: note: 'val' was declared here
      __u32 val;
            ^
So just shut it up by initializing to 0.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 ip/iproute.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ip/iproute.c b/ip/iproute.c
index c42ea0b..867c8da 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -572,7 +572,7 @@ int print_route(const struct sockaddr_nl *who, struct nlmsghdr *n, void *arg)
 			mxlock = *(unsigned*)RTA_DATA(mxrta[RTAX_LOCK]);
 
 		for (i=2; i<= RTAX_MAX; i++) {
-			__u32 val;
+			__u32 val = 0;
 
 			if (mxrta[i] == NULL)
 				continue;
-- 
1.9.3

Re: [PATCH iproute2] ip, route: fix minor compile warning

[Phil Sutter]

On Mon, Dec 14, 2015 at 04:34:29PM +0100, Daniel Borkmann wrote:
> Seems like gcc (4.8.3) doesn't catch this false positive, triggering
> after 0f7543322c5f ("route: ignore RTAX_HOPLIMIT of value -1"):
> 
>   iproute.c: In function 'print_route':
>   iproute.c:301:12: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
>      features &= ~RTAX_FEATURE_ECN;
>               ^
>   iproute.c:575:10: note: 'val' was declared here
>       __u32 val;
>             ^
> So just shut it up by initializing to 0.

Hmm. Interestingly, my patch shouldn't have changed anything relevant
for gcc's decision. OTOH, I don't see a warning using gcc-4.9.3.

Cheers, Phil

Re: [PATCH iproute2] ip, route: fix minor compile warning

[Daniel Borkmann]

On 12/14/2015 04:51 PM, Phil Sutter wrote:
> On Mon, Dec 14, 2015 at 04:34:29PM +0100, Daniel Borkmann wrote:
>> Seems like gcc (4.8.3) doesn't catch this false positive, triggering
>> after 0f7543322c5f ("route: ignore RTAX_HOPLIMIT of value -1"):
>>
>>    iproute.c: In function 'print_route':
>>    iproute.c:301:12: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
>>       features &= ~RTAX_FEATURE_ECN;
>>                ^
>>    iproute.c:575:10: note: 'val' was declared here
>>        __u32 val;
>>              ^
>> So just shut it up by initializing to 0.
>
> Hmm. Interestingly, my patch shouldn't have changed anything relevant
> for gcc's decision. OTOH, I don't see a warning using gcc-4.9.3.

If I revert it, the warning is gone for me ;) perhaps some heuristic issue
with that gcc version.

Cheers,
Daniel

Re: [PATCH iproute2] ip, route: fix minor compile warning

[Stephen Hemminger]

On Mon, 14 Dec 2015 16:53:20 +0100
Daniel Borkmann <daniel@iogearbox.net> wrote:

> On 12/14/2015 04:51 PM, Phil Sutter wrote:
> > On Mon, Dec 14, 2015 at 04:34:29PM +0100, Daniel Borkmann wrote:
> >> Seems like gcc (4.8.3) doesn't catch this false positive, triggering
> >> after 0f7543322c5f ("route: ignore RTAX_HOPLIMIT of value -1"):
> >>
> >>    iproute.c: In function 'print_route':
> >>    iproute.c:301:12: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
> >>       features &= ~RTAX_FEATURE_ECN;
> >>                ^
> >>    iproute.c:575:10: note: 'val' was declared here
> >>        __u32 val;
> >>              ^
> >> So just shut it up by initializing to 0.
> >
> > Hmm. Interestingly, my patch shouldn't have changed anything relevant
> > for gcc's decision. OTOH, I don't see a warning using gcc-4.9.3.
> 
> If I revert it, the warning is gone for me ;) perhaps some heuristic issue
> with that gcc version.
> 
> Cheers,
> Daniel

I don't see this warning on current master with gcc 4.9.2.

Re: [PATCH iproute2] ip, route: fix minor compile warning

[Daniel Borkmann]

On 12/18/2015 02:12 AM, Stephen Hemminger wrote:
> On Mon, 14 Dec 2015 16:53:20 +0100
> Daniel Borkmann <daniel@iogearbox.net> wrote:
>
>> On 12/14/2015 04:51 PM, Phil Sutter wrote:
>>> On Mon, Dec 14, 2015 at 04:34:29PM +0100, Daniel Borkmann wrote:
>>>> Seems like gcc (4.8.3) doesn't catch this false positive, triggering
>>>> after 0f7543322c5f ("route: ignore RTAX_HOPLIMIT of value -1"):
>>>>
>>>>     iproute.c: In function 'print_route':
>>>>     iproute.c:301:12: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]
>>>>        features &= ~RTAX_FEATURE_ECN;
>>>>                 ^
>>>>     iproute.c:575:10: note: 'val' was declared here
>>>>         __u32 val;
>>>>               ^
>>>> So just shut it up by initializing to 0.
>>>
>>> Hmm. Interestingly, my patch shouldn't have changed anything relevant
>>> for gcc's decision. OTOH, I don't see a warning using gcc-4.9.3.
>>
>> If I revert it, the warning is gone for me ;) perhaps some heuristic issue
>> with that gcc version.
>>
>> Cheers,
>> Daniel
>
> I don't see this warning on current master with gcc 4.9.2.

Well, in the commit message I wrote 4.8.3 ... but I don't mind if we drop it, sure.