[ovs-dev] [PATCH] netdev-vport: Fix compilation warning

Roi Dayan roid at nvidia.com
Thu Nov 18 07:59:24 UTC 2021



On 2021-11-17 5:45 PM, Kevin Traynor wrote:
> On 17/11/2021 14:44, Eelco Chaudron wrote:
>>
>>
>> On 17 Nov 2021, at 14:00, Roi Dayan via dev wrote:
>>
>>> On 2021-11-17 2:51 PM, Roi Dayan wrote:
>>>>
>>>>
>>>> On 2021-11-17 2:42 PM, Roi Dayan wrote:
>>>>>
>>>>>
>>>>> On 2021-11-17 2:23 PM, Roi Dayan wrote:
>>>>>>
>>>>>>
>>>>>> On 2021-11-17 2:17 PM, David Marchand wrote:
>>>>>>> On Wed, Nov 17, 2021 at 1:12 PM Roi Dayan via dev
>>>>>>> <ovs-dev at openvswitch.org> wrote:
>>>>>>>>
>>>>>>>> port is declared as uint16 so use %hu specifier instead of %d.
>>>>>>>>
>>>>>>>> lib/netdev-vport.c:460:44: error: '%s' directive output may be 
>>>>>>>> truncated writing up to 4 bytes into a region of size between 1 
>>>>>>>> and 10 [-Werror=format-truncation=]
>>>>>>>>         snprintf(namebuf, bufsize, "dst_port_%d%s",
>>>>>>>>                                              ^~
>>>>>>>
>>>>>>> Out of curiosity, is it due to new checks from a recent compiler?
>>>>>>
>>>>>> do you mean if we updated the compiler? than no.
>>>>>> it fails on powerpc machine.
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Fixes: 189de33f02b2 ("netdev-vport: reject concomitant 
>>>>>>>> incompatible tunnels")
>>>>>>>> Signed-off-by: Roi Dayan <roid at nvidia.com>
>>>>>>>> Reviewed-by: Eli Britstein <elibr at nvidia.com>
>>>>>>>> ---
>>>>>>>>    lib/netdev-vport.c | 2 +-
>>>>>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/lib/netdev-vport.c b/lib/netdev-vport.c
>>>>>>>> index 499c0291c933..1c7f55757e9a 100644
>>>>>>>> --- a/lib/netdev-vport.c
>>>>>>>> +++ b/lib/netdev-vport.c
>>>>>>>> @@ -457,7 +457,7 @@ static char *
>>>>>>>>    vxlan_get_port_ext_gbp_str(uint16_t port, bool gbp,
>>>>>>>>                               char namebuf[], size_t bufsize)
>>>>>>>>    {
>>>>>>>> -    snprintf(namebuf, bufsize, "dst_port_%d%s",
>>>>>>>> +    snprintf(namebuf, bufsize, "dst_port_%hu%s",
>>>>>>>>                 port, gbp ? "_gbp" : "");
>>>>>>>
>>>>>>> Format for uint16_t is PRIu16.
>>>>>>
>>>>>> tested PRIu16 and got the same error. isn't PRIu16 defined as "u" ?
>>>>>>
>>>>>
>>>>> did some more tests.
>>>>> the test machine is ppc64be.
>>>>>
>>>>> lib/netdev-vport.c:460:51: note: format string is defined here
>>>>>        snprintf(namebuf, bufsize, "dst_port_%"PRIu16"%s",
>>>>>                                                      ^~
>>>>>
>>>>> seems the compiler now complains on the string.
>>>>> if i remove the string the compiler doesn't complain with either %d
>>>>> or PRIu16.
>>>>
>>>> seems i got it wrong. the compiler identify the size passed is 20.
>>>> %hu solved it by limiting the number and have room for the string 
>>>> "_gbp".
>>>> using PRIu16 is bigger than %hu allowing to pass the 20 chars size.
>>>> i'll send a diff fix increasing the buf size to 24 and using PRIu16
>>>> as should.
>>>>
>>>> thanks for the review.
>>>>
>>>>
>>>
>>> before submitting i'm trying to understand why the compiler suggests 24.
>>> "dst_port_" is 9 and the port could be 2. then "_gbp" is 4. so 20
>>> should be enough. someone has an idea?
>>> I can reproduce the issue only on ppc64be.
>>
>> Don’t have a ppc64be compiler ready, but what is the size of an int on 
>> that architecture?
>> %d normally is an int, so if 32 bit the max value for the string could 
>> be strlen(“-2147483648”).
>>
> 
> There is an INT_STRLEN() macro in 
> https://github.com/openvswitch/ovs/blob/master/include/openvswitch/type-props.h which is used elsewhere in the code and might be useful here.
> 

thanks. I checked size for int, uint16 and char with this macro.

2021-11-18T07:57:28Z|00020|dpif_netlink|INFO|XXX size uint16_t 6
2021-11-18T07:57:28Z|00021|dpif_netlink|INFO|XXX size int 12
2021-11-18T07:58:58Z|00047|dpif_netlink|INFO|XXX size char 3


>> //Eelco
>>
>>
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> 


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