linux-kernel - Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

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Date:   Fri, 14 Oct 2016 05:57:25 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Nilay Vaish <nilayvaish@...il.com>,
        Linux Kernel list <linux-kernel@...r.kernel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "mingo@...e.hu" <mingo@...e.hu>,
        Anton Blanchard <anton@...abs.org>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH 1/9] perf/jit: improve error messages from JVMTI

On Fri, Oct 14, 2016 at 4:13 AM, Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
> Em Thu, Oct 13, 2016 at 03:05:40PM -0500, Nilay Vaish escreveu:
>> On 13 October 2016 at 05:59, Stephane Eranian <eranian@...gle.com> wrote:
>> > +++ b/tools/perf/jvmti/libjvmti.c
>> > @@ -12,6 +12,17 @@
>> > +static void print_error(jvmtiEnv *jvmti, const char *msg, jvmtiError ret)
>> > +{
>> > +       char *err_msg = NULL;
>> > +       jvmtiError err;
>> > +       err = (*jvmti)->GetErrorName(jvmti, ret, &err_msg);
>> > +       if (err == JVMTI_ERROR_NONE) {
>> > +               warnx("%s failed with %s", msg, err_msg);
>> > +               (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
>> > +       }
>> > +}
>>
>> Do we not need to release the memory for err_msg if the condition for
>> the 'if' statement evaluates to false?  Is it that we are going to
>> kill the process, so no need to release the memory?
>
> I guess that print_error() is called only when an error was returned
> somewhere, that ret parameter, then if there was no error
> (JVMTI_ERROR_NONE) in translating that numeric code to an string,
> err_msg, it can then be used with warnx() (the main purpose of
> print_error()) and then deallocated.
>
> For err != JVMTI_ERROR_NONE it silently goes back to the caller that
> expected it to print something.
>
> I.e. probably it should have an else clause, something like:
>
>         if (err == JVMTI_ERROR_NONE) {
>                 warnx("%s failed with %s", msg, err_msg);
>                 (*jvmti)->Deallocate(jvmti, (unsigned char *)err_msg);
>         } else {
>                 warnx("%s failed with an unknown error %d", msg, (int)ret);
>         }
>
> Stephane?
>'I will fix all of the comments over the week-end. I am away from office today.

> - Arnaldo