linux-kernel - Re: tracing: Add support for dynamic strings to synthetic events

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Message-ID: <cfcfa79c-580c-7e36-3b23-072d7e105eaf@canonical.com>
Date:   Wed, 7 Oct 2020 14:35:07 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Tom Zanussi <zanussi@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: tracing: Add support for dynamic strings to synthetic events

On 07/10/2020 14:30, Steven Rostedt wrote:
> On Wed, 7 Oct 2020 14:08:38 +0100
> Colin Ian King <colin.king@...onical.com> wrote:
> 
>> Hi,
>>
>> Static analysis with Coverity has detected a duplicated condition in an
>> if statement in the following commit in source
>> kernel/trace/trace_events_synth.c
>>
>> commit bd82631d7ccdc894af2738e47abcba2cb6e7dea9
>> Author: Tom Zanussi <zanussi@...nel.org>
>> Date:   Sun Oct 4 17:14:06 2020 -0500
>>
>>     tracing: Add support for dynamic strings to synthetic events
>>
>> Analysis is as follows:
>>
>> 493        for (i = 0; i < event->n_fields; i++) {
>>
>> Same on both sides (CONSTANT_EXPRESSION_RESULT)
>> pointless_expression: The expression event->fields[i]->is_dynamic &&
>> event->fields[i]->is_dynamic does not accomplish anything because it
>> evaluates to either of its identical operands, event->fields[i]->is_dynamic.
>>
>>    Did you intend the operands to be different?
>>
>> 494                if (event->fields[i]->is_dynamic &&
>> 495                    event->fields[i]->is_dynamic)
> 
> Bah, I believe that was suppose to be:
> 
> 		if (event->fields[i]->is_string &&
> 		    event->fields[i]->is_dynamic)
> 
> I'll go and fix that.

Ah, makes sense. Thanks!

> 
> -- Steve
> 
>> 496                        pos += snprintf(buf + pos, LEN_OR_ZERO,
>> 497                                ", __get_str(%s)",
>> event->fields[i]->name);
>> 498                else
>> 499                        pos += snprintf(buf + pos, LEN_OR_ZERO,
>> 500                                        ", REC->%s",
>> event->fields[i]->name);
>> 501        }
>>
>> Colin
>