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[0], ckhdid->data[1],
> > ^~~~~~~~~~~~~~~
>
> 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. When
considering integer promotions it's difficult to say if this is
"wrong", 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?
>
> > ckhdid->data is unconditionally defined as `u8 data[16]`, so this patch
> > updates the format characters to the correct one for unsigned char types.
> []
> > diff --git a/include/linux/usb/wusb.h b/include/linux/usb/wusb.h
> []
> > @@ -240,8 +240,8 @@ static inline size_t ckhdid_printf(char *pr_ckhdid, size_t size,
> > const struct wusb_ckhdid *ckhdid)
> > {
> > return scnprintf(pr_ckhdid, size,
> > - "%02hx %02hx %02hx %02hx %02hx %02hx %02hx %02hx "
> > - "%02hx %02hx %02hx %02hx %02hx %02hx %02hx %02hx",
> > + "%02hhx %02hhx %02hhx %02hhx %02hhx %02hhx %02hhx %02hhx "
> > + "%02hhx %02hhx %02hhx %02hhx %02hhx %02hhx %02hhx %02hhx",
> > ckhdid->data[0], ckhdid->data[1],
> > ckhdid->data[2], ckhdid->data[3],
> > ckhdid->data[4], ckhdid->data[5],
>
> Better to use the vsprintf %ph extension insead.
Agreed, so I guess my previous comment is irrelevant in this scenario.
> ---
> include/linux/usb/wusb.h | 12 +-----------
> 1 file changed, 1 insertion(+), 11 deletions(-)
>
> diff --git a/include/linux/usb/wusb.h b/include/linux/usb/wusb.h
> index 9e4a3213f2c2..8c39ddf62951 100644
> --- a/include/linux/usb/wusb.h
> +++ b/include/linux/usb/wusb.h
> @@ -239,17 +239,7 @@ enum {
> static inline size_t ckhdid_printf(char *pr_ckhdid, size_t size,
> const struct wusb_ckhdid *ckhdid)
> {
> - return scnprintf(pr_ckhdid, size,
> - "%02hx %02hx %02hx %02hx %02hx %02hx %02hx %02hx "
> - "%02hx %02hx %02hx %02hx %02hx %02hx %02hx %02hx",
> - ckhdid->data[0], ckhdid->data[1],
> - ckhdid->data[2], ckhdid->data[3],
> - ckhdid->data[4], ckhdid->data[5],
> - ckhdid->data[6], ckhdid->data[7],
> - ckhdid->data[8], ckhdid->data[9],
> - ckhdid->data[10], ckhdid->data[11],
> - ckhdid->data[12], ckhdid->data[13],
> - ckhdid->data[14], ckhdid->data[15]);
> + return scnprintf(pr_ckhdid, size, "%16ph", ckhdid->data);
> }
>
> /*
>
>
