Re: [usb:usb-testing 7/12] drivers/usb/dwc3/core.c:1482:69: warning: '%d' directive output may be truncated writing between 1 and 11 bytes into a region of size 4

[Krishna Kurapati PSSNV <quic_kriskura@quicinc.com>]

On 4/24/2024 12:11 PM, Johan Hovold wrote:
> On Wed, Apr 24, 2024 at 01:03:07PM +0800, kernel test robot wrote:
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
>> head:   a160e1202ca318a85c70cf5831f172cc79a24c57
>> commit: 846b4bacf2d48212f271fc1ef7488bcdf2c75bcb [7/12] usb: dwc3: core: Refactor PHY logic to support Multiport Controller
>> config: s390-allyesconfig (https://download.01.org/0day-ci/archive/20240424/202404241215.Mib19Cu7-lkp@intel.com/config)
>> compiler: s390-linux-gcc (GCC) 13.2.0
>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240424/202404241215.Mib19Cu7-lkp@intel.com/reproduce)
>>
>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>> the same patch/commit), kindly add following tags
>> | Reported-by: kernel test robot <lkp@intel.com>
>> | Closes: https://lore.kernel.org/oe-kbuild-all/202404241215.Mib19Cu7-lkp@intel.com/
>>
>> All warnings (new ones prefixed by >>):
>>
>>     drivers/usb/dwc3/core.c: In function 'dwc3_core_get_phy':
>>>> drivers/usb/dwc3/core.c:1482:69: warning: '%d' directive output may be truncated writing between 1 and 11 bytes into a region of size 4 [-Wformat-truncation=]
>>      1482 |                         snprintf(phy_name, sizeof(phy_name),  "usb2-%d", i);
>>           |                                                                     ^~
>>     drivers/usb/dwc3/core.c:1482:63: note: directive argument in the range [-2147483641, 254]
>>      1482 |                         snprintf(phy_name, sizeof(phy_name),  "usb2-%d", i);
> 
> This version or s390-build of gcc appears to be confused as the
> variable i is clearly in the range [0,254] in these for loops.
> 
> I also don't see this W=1 warning with my gcc-10 (aarch64).
> 
> It may be possible to work around this by using u8 type for the iterator
> (and %u in the format), but I'm not sure we should be working around
> compiler bugs like that.

Thanks Johan. i agree it looks like a bogus compiler warning, but I 
think your suggestion of changing to u8 should work, if only to placate 
the compiler.

Greg, do you think I should go ahead and update it in v22 or can we 
ignore this warning ?

> 
>>           |                                                               ^~~~~~~~~
>>     drivers/usb/dwc3/core.c:1482:25: note: 'snprintf' output between 7 and 17 bytes into a destination of size 9
>>      1482 |                         snprintf(phy_name, sizeof(phy_name),  "usb2-%d", i);
>>           |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
>>    1446	static int dwc3_core_get_phy(struct dwc3 *dwc)
>>    1447	{
> 
>>    1450		char phy_name[9];
>>    1451		int ret;
>>    1452		int i;
> 
>>    1478		for (i = 0; i < dwc->num_usb2_ports; i++) {
>>    1479			if (dwc->num_usb2_ports == 1)
>>    1480				snprintf(phy_name, sizeof(phy_name), "usb2-phy");
>>    1481			else
>>> 1482				snprintf(phy_name, sizeof(phy_name),  "usb2-%d", i);
> 
>>    1493		}
> 
> Johan