Re: [PATCH v2] wusb: use correct format characters
From: Joe Perches
Date: Thu Feb 28 2019 - 18:10:22 EST
On Thu, 2019-02-28 at 14:23 -0800, Jon Flatley wrote:
> Thanks for the patch and comments.
> On Thu, Feb 28, 2019 at 1:53 PM Joe Perches <joe@xxxxxxxxxxx> wrote:
> > On Thu, 2019-02-28 at 12:24 +0000, Louis Taylor wrote:
> > > When compiling with -Wformat, clang warns:
> > > ./include/linux/usb/wusb.h:245:5: warning: format specifies type
> > > 'unsigned short' but the argument has type 'u8' (aka 'unsigned char')
> > > [-Wformat]
> > > ckhdid->data, ckhdid->data,
> > > ^~~~~~~~~~~~~~~
> > I think the message is somewhat misguided as all the
> > vararg arguments have implicit integer promotions.
> That's a fair point, but Clang checks the arguments against their
> format specifier before they're promoted when using -Wformat.
Perhaps clang could be a bit more verbose if
checking signed types emitted as unsigned or
unsigned types emitted as signed instead.
> considering integer promotions it's difficult to say if this is
I didn't write "wrong", I wrote misguided.
> but since 'unsigned char' corresponds to the "hh" length
> specifier I don't think this is misguided. Otherwise, why use the "h"
> length specifier at all?
e.g.: signed char as %x needs %hhx