> Date: Mon, 7 Aug 2017 11:04:51 +0200 (CEST)
> From: Markus Hennecke <[email protected]>
>
> On Thu, 3 Aug 2017, Mark Kettenis wrote:
>
> > Currently clang ignores the "kprintf" format attribute. I've got a
> > fix for that, but with that fix it complains about the code fixed in
> > the diff below.
> >
> > Now our manual page says:
> >
> > FORMAT OPTIONS
> > The kernel functions don't support as many formatting specifiers as
> > their
> > user space counterparts. In addition to the floating point formatting
> > specifiers, the following integer type specifiers are not supported:
> >
> > %hh Argument of char type. This format specifier is accepted by the
> > kernel but will be handled as %h.
> >
> > So as far as the kernel is concerned, this change is a no-op.
> >
> > ok?
> >
> > P.S. While printing as a short is technically incorrect, it works
> > because the arguments are unsigned and promoted to int.
> >
> >
> > Index: subr_disk.c
> > ===================================================================
> > RCS file: /cvs/src/sys/kern/subr_disk.c,v
> > retrieving revision 1.230
> > diff -u -p -r1.230 subr_disk.c
> > --- subr_disk.c 4 May 2017 22:47:27 -0000 1.230
> > +++ subr_disk.c 3 Aug 2017 17:38:32 -0000
> > @@ -1864,7 +1864,7 @@ duid_format(u_char *duid)
> > static char duid_str[17];
> >
> > snprintf(duid_str, sizeof(duid_str),
> > - "%02hx%02hx%02hx%02hx%02hx%02hx%02hx%02hx",
> > + "%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx",
> > duid[0], duid[1], duid[2], duid[3],
> > duid[4], duid[5], duid[6], duid[7]);
>
> This breaks kernel builds with gcc. It looks like gcc in base is too old
> for handling %hhx. I tried to build a kernel for armv7 with rev 1.231
> today.
Damn. Thanks for spotting this. It is fairly easy to add %hh support
to our gcc, but maybe we shouldn't.
So here is an alternative approach. Just cast to u_short in
recognition that this is what the kernel actually supports.
ok?
Index: kern/subr_disk.c
===================================================================
RCS file: /cvs/src/sys/kern/subr_disk.c,v
retrieving revision 1.231
diff -u -p -r1.231 subr_disk.c
--- kern/subr_disk.c 6 Aug 2017 19:56:29 -0000 1.231
+++ kern/subr_disk.c 7 Aug 2017 09:30:29 -0000
@@ -1864,9 +1864,10 @@ duid_format(u_char *duid)
static char duid_str[17];
snprintf(duid_str, sizeof(duid_str),
- "%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx%02hhx",
- duid[0], duid[1], duid[2], duid[3],
- duid[4], duid[5], duid[6], duid[7]);
+ "%02hx%02hx%02hx%02hx%02hx%02hx%02hx%02hx",
+ (u_short)duid[0], (u_short)duid[1], (u_short)duid[2],
+ (u_short)duid[3], (u_short)duid[4], (u_short)duid[5],
+ (u_short)duid[6], (u_short)duid[7]);
return (duid_str);
}
