Re: ftrace breaks sparc64 build

Heiko Carstens
2009-01-06T09:37:38Z

On Mon, Jan 05, 2009 at 09:07:05PM -0500, Steven Rostedt wrote:
> On Tue, 6 Jan 2009, Heiko Carstens wrote:
> > On Mon, Jan 05, 2009 at 05:14:22PM -0500, Steven Rostedt wrote:
> > > On Mon, 5 Jan 2009, Sam Ravnborg wrote:
> > >
> > > > > Is this all sparc cross compiler? I'm trying to reproduce it on x86 with
> > > > > no avail :-(
> > > > >
> > > > > I would like to test other ways to change the macro, but to do so, I need
> > > > > to get a compiler that will produce the warnings that you see. What
> > > > > version of gcc are you using?
> > > >
> > > > I used crosstool to build a 3.4.5 gcc:
> > >
> > > Hmm, that's a pretty old compiler. I wonder if it wouldn't just help
> > > if we just make the branch tracer dependent on the compiler used. That is.
> > >
> > > #if defined(CONFIG_PROFILE_ALL_BRANCHES) && (__GNUC__ >= 4)
> > > #define if(cond) ...
> > >
> > > Or something :-/
> >
> > FWIW, on s390 with gcc 4.3.2 and an allyesconfig I get these:
> >
> > CC arch/s390/mm/extmem.o
> > arch/s390/mm/extmem.c: In function 'segment_modify_shared':
> > arch/s390/mm/extmem.c:572: warning: 'end_addr' may be used uninitialized in this function
> > arch/s390/mm/extmem.c:572: warning: 'start_addr' may be used uninitialized in this function
> > arch/s390/mm/extmem.c: In function 'query_segment_type':
> > arch/s390/mm/extmem.c:259: warning: 'vmrc' may be used uninitialized in this function
> >
> > Switching off PROFILE_ALL_BRANCHES makes the warnings go away again.
>
> Now that is really interesting. Because end_addr and start_addr are
> initialized via functions:
>
> if (x)
> init_me(a, &y);
> else
> init_me(b, &y);
>
> Which actually does not make sense why turning off PROFILE_ALL_BRANCHES
> would affect this :-/

They are not necessarily initialized via 'initme'. Only if it returns with
a return value >= 0. So it's a bit more complex:

if (x)
rc = init_me(a, &y);
else
rc = init_me(b, &y);
if (rc < 0)
/* y unitialized */
return;
use(y);