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

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Message-ID: <d34dccd5-96ba-a2d9-46ea-de8807525deb@canonical.com>
Date:   Wed, 7 Oct 2020 14:08:38 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Tom Zanussi <zanussi@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.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

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)
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