lkml.org 
[lkml]   [2014]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] misc: suppress build warning
On Thu, 4 Dec 2014 08:30:32 -0800 Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:

> On Thu, Dec 04, 2014 at 03:13:00PM +0000, Prabhakar Lad wrote:
> > On Thu, Dec 4, 2014 at 2:59 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> > > On Thursday 04 December 2014 14:38:30 Lad, Prabhakar wrote:
> > >> this patch fixes following build warning:
> > >>
> > >> drivers/misc/ioc4.c: In function ___ioc4_probe___:
> > >> drivers/misc/ioc4.c:194:16: warning: ___start___ may be used uninitialized in this function [-Wmaybe-uninitialized]
> > >> period = (end - start) /
> > >> ^
> > >> drivers/misc/ioc4.c:148:11: note: ___start___ was declared here
> > >> uint64_t start, end, period;
> > >>
> > >> Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
> > >
> > > Please explain why the compiler thinks there is a bug, why you
> > > are sure that there isn't, and why you picked '0' as the
> > > initialization value.
> > >
> > Its a false positive, to suppress the warning '0' was picked.
>
> Are you _sure_ it's a false positive? That odd do/while loop looks like
> it might just not ever initialize the start variable, are you sure the
> logic there is correct?
>

As long as IOC4_CALIBRATE_END is greater than IOC4_CALIBRATE_DISCARD (it is),
`start' is written to.

It would be nice to simplify the code, but I'm not sure how.

And I really dislike this initialize-it-to-zero-to-stop-the-warning
thing which we do all over the place. The reader doesn't know *why*
it's initialized to zero and the initialization can conceal bugs if we
get a code path which should have written to it but forgot to. And it
adds unneeded code to vlinux.

I much prefer unintialized_var() which fixes the documentation issue
and doesn't add code. But Linus and Ingo had a dummy-spit over it.


\
 
 \ /
  Last update: 2014-12-05 09:01    [W:0.045 / U:0.500 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site