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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Apr 25, 2024 at 10:38:47AM +0530, Krishna Kurapati PSSNV wrote:
> 
> 
> 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 ?

Please send a follow-on patch to fix this, I'll leave it as-is in my
tree for now.

thanks,

greg k-h