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Date: Mon, 13 Feb 2017 14:20:20 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] building libtraceevent with clang
Em Mon, Feb 13, 2017 at 12:14:18PM -0500, Steven Rostedt escreveu:
> On Mon, 13 Feb 2017 13:26:22 -0300
> Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
>
>
> > > diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
> > > index 65984f1c2974..2009cb7d9675 100644
> > > --- a/tools/lib/traceevent/kbuffer-parse.c
> > > +++ b/tools/lib/traceevent/kbuffer-parse.c
> > > @@ -315,6 +315,7 @@ static unsigned int old_update_pointers(struct kbuffer *kbuf)
> > > extend += delta;
> > > delta = extend;
> > > ptr += 4;
> > > + lenght = 0;
> >
> > ouch, 'length' :-)
> >
> > clang provides a really nice error message:
> >
> > kbuffer-parse.c:318:3: error: use of undeclared identifier 'lenght'; did you mean 'length'?
> > lenght = 0;
> > ^~~~~~
> > length
> > kbuffer-parse.c:297:15: note: 'length' declared here
> > unsigned int length;
> > ^
> > 1 error generated.
> >
> > I only had to test compile it :-)
> >
> > > break;
> > >
> > > case OLD_RINGBUF_TYPE_TIME_STAMP:
> > >
>
> OK, I pulled the patch into git, and made it official ;-)
> I also fixed the "lenght" in the change log too.
>
> Could you use this instead.
Sure, now take a look at this another one:
commit 6401e4361df183bd9953dce56f7c51d8ef28b11e
Author: Arnaldo Carvalho de Melo <acme@...hat.com>
Date: Mon Feb 13 13:33:57 2017 -0300
tools lib traceevent plugin function: Initialize 'index' variable
Detected with clang:
CC /tmp/build/perf/plugin_function.o
plugin_function.c:145:6: warning: variable 'index' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
if (parent && ftrace_indent->set)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~
plugin_function.c:148:29: note: uninitialized use occurs here
trace_seq_printf(s, "%*s", index*3, "");
^~~~~
plugin_function.c:145:2: note: remove the 'if' if its condition is always true
if (parent && ftrace_indent->set)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
plugin_function.c:145:6: warning: variable 'index' is used uninitialized whenever '&&' condition is false [-Wsometimes-uninitialized]
if (parent && ftrace_indent->set)
^~~~~~
plugin_function.c:148:29: note: uninitialized use occurs here
trace_seq_printf(s, "%*s", index*3, "");
^~~~~
plugin_function.c:145:6: note: remove the '&&' if its condition is always true
if (parent && ftrace_indent->set)
^~~~~~~~~
plugin_function.c:133:11: note: initialize the variable 'index' to silence this warning
int index;
^
= 0
2 warnings generated.
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/n/tip-b5wyjocel55gorl2jq2cbxrr@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
diff --git a/tools/lib/traceevent/plugin_function.c b/tools/lib/traceevent/plugin_function.c
index a00ec190821a..42dbf73758f3 100644
--- a/tools/lib/traceevent/plugin_function.c
+++ b/tools/lib/traceevent/plugin_function.c
@@ -130,7 +130,7 @@ static int function_handler(struct trace_seq *s, struct pevent_record *record,
unsigned long long pfunction;
const char *func;
const char *parent;
- int index;
+ int index = 0;
if (pevent_get_field_val(s, event, "ip", record, &function, 1))
return trace_seq_putc(s, '!');
> -- Steve
>
>
> From 4f060a0577156acfdc0524a634f4afcc1657c929 Mon Sep 17 00:00:00 2001
> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> Date: Mon, 13 Feb 2017 12:11:44 -0500
> Subject: [PATCH] tools lib traceevent: Initialize lenght on
> OLD_RING_BUFFER_TYPE_TIME_STAMP
>
> A undefined value was being used for the OLD_RING_BUFFER_TYPE_TIME_STAMP
> case entry, as the 'length' variable was not being initialized, fix it.
>
> Caught by the reporter when building tools/perf/ using clang, which emmitted
> this warning:
>
> kbuffer-parse.c:312:7: warning: variable 'length' is used uninitialized whenever switch case is taken [-Wsometimes-uninitialized]
> case OLD_RINGBUF_TYPE_TIME_EXTEND:
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> kbuffer-parse.c:339:29: note: uninitialized use occurs here
> kbuf->next = kbuf->index + length;
> ^~~~~~
> kbuffer-parse.c:297:21: note: initialize the variable 'length' to silence this warning
> unsigned int length;
> ^
> = 0
>
> Reported-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: David Ahern <dsahern@...il.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Wang Nan <wangnan0@...wei.com>
> Link: http://lkml.kernel.org/r/20170210141408.5eeb6e91@gandalf.local.home
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
> tools/lib/traceevent/kbuffer-parse.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/tools/lib/traceevent/kbuffer-parse.c b/tools/lib/traceevent/kbuffer-parse.c
> index 65984f1..c94e364 100644
> --- a/tools/lib/traceevent/kbuffer-parse.c
> +++ b/tools/lib/traceevent/kbuffer-parse.c
> @@ -315,6 +315,7 @@ static unsigned int old_update_pointers(struct kbuffer *kbuf)
> extend += delta;
> delta = extend;
> ptr += 4;
> + length = 0;
> break;
>
> case OLD_RINGBUF_TYPE_TIME_STAMP:
> --
> 2.9.3
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