Re: [PATCH v2] byteswap: try to avoid __builtin_constant_p gcc bug

[Andrew Morton]

On Tue, 03 May 2016 01:10:16 +0200 Arnd Bergmann <arnd@xxxxxxxx> wrote:

> On Monday 02 May 2016 16:02:18 Andrew Morton wrote:
> > On Mon, 02 May 2016 23:48:19 +0200 Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > 
> > > This is another attempt to avoid a regression in wwn_to_u64() after
> > > that started using get_unaligned_be64(), which in turn ran into a
> > > bug on gcc-4.9 through 6.1.
> > 
> > I'm still getting a couple screenfuls of things like
> > 
> > net/tipc/name_distr.c: In function 'tipc_named_process_backlog':
> > net/tipc/name_distr.c:330: warning: format '%u' expects type 'unsigned int', but argument 3 has type 'unsigned int'
> > net/tipc/name_distr.c:330: warning: format '%u' expects type 'unsigned int', but argument 4 has type 'unsigned int'
> > net/tipc/name_distr.c:330: warning: format '%u' expects type 'unsigned int', but argument 5 has type 'unsigned int'
> > net/tipc/name_distr.c:330: warning: format '%u' expects type 'unsigned int', but argument 7 has type 'unsigned int'
> 
> I've built a few thousand kernels (arm32 with gcc-6.1) with the patch applied,
> but didn't see this one. What target architecture and compiler version produced
> this? Does it go away if you add a (__u32) cast? I don't even know what the
> warning is trying to tell me.

heh, I didn't actually read it.

Hopefully we can write this off as a gcc-4.4.4 glitch. 4.8.4 is OK.