Re: [PATCH 1/3] tools lib traceevent: Add -O2 option to traceevent

[Arnaldo Carvalho de Melo]

Em Wed, Oct 19, 2016 at 03:05:48PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Oct 19, 2016 at 02:48:45PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Tue, Oct 18, 2016 at 11:29:53AM -0400, Steven Rostedt escreveu:
> > > On Tue, 18 Oct 2016 11:01:09 +0900
> > > Namhyung Kim <namhy...@kernel.org> wrote:
> > > 
> > > > Hi Honggyu,
> > > > 
> > > > You need to CC relevant maintainers when you send patches to LKML.
> > > > For the libtraceevent, they are Arnaldo and Steven.  You can use
> > > > scripts/get_maintainer.pl for this job later.  In addition running
> > > > scripts/checkpatch.pl before sending patches is a good habit.
> > > > 
> > > > Arnaldo and Steve,
> > > > 
> > > > This is from uftrace building libtraceevent with the optimization flag
> > > > and we want to fix the upstream as well.
> > > > 
> > > 
> > > Acked-by: Steven Rostedt <rost...@goodmis.org>
> > 
> > So right after applying this patch I get these new warnings, 
> > investigating...
> 
> Some are the compiler not grokking logic where the compiler gets
> confused with logic that tests one variable to use another and thinks it
> is using garbage (uninitialized stuff), I tried to follow the logic and
> I think it got slightly more confused than me, as I _think_ its not a
> problem, but the one on the case entry for
> 
>   OLD_RINGBUF_TYPE_TIME_EXTEND
> 
> in old_update_pointers() looks like a bug, unless some macro magic is
> taking place that updates that 'lenght' variable.
> 
> Rostedt, that -O2 unleashed some warnings, please check, I'll defer
> applying those patches till it doesn't show these warnings, i.e. till
> other patches fixing these issues or simply silencing the compiler with
> a harmless init gets submitted,

Ah, the patch I had so far shutting off most of this is:


diff --git a/tools/lib/traceevent/event-parse.c 
b/tools/lib/traceevent/event-parse.c
index 664c90c8e22b..449056e96fe6 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -3490,7 +3490,7 @@ struct event_format *
 pevent_find_event_by_name(struct pevent *pevent,
                          const char *sys, const char *name)
 {
-       struct event_format *event;
+       struct event_format *event = NULL;
        int i;
 
        if (pevent->last_event &&
@@ -4843,7 +4843,7 @@ static void pretty_print(struct trace_seq *s, void *data, 
int size, struct event
        char format[32];
        int show_func;
        int len_as_arg;
-       int len_arg;
+       int len_arg = 0;
        int len;
        int ls;
 
@@ -5102,8 +5102,8 @@ void pevent_data_lat_fmt(struct pevent *pevent,
        static int migrate_disable_exists;
        unsigned int lat_flags;
        unsigned int pc;
-       int lock_depth;
-       int migrate_disable;
+       int lock_depth = 0;
+       int migrate_disable = 0;
        int hardirq;
        int softirq;
        void *data = record->data;