linux-kernel - Re: [PATCH v2 1/9] perf tools: add parse events append error

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Date:   Wed, 23 Oct 2019 10:36:08 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andi Kleen <ak@...ux.intel.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        John Garry <john.garry@...wei.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, clang-built-linux@...glegroups.com,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v2 1/9] perf tools: add parse events append error

On Tue, Oct 22, 2019 at 05:53:29PM -0700, Ian Rogers wrote:
> Parse event error handling may overwrite one error string with another
> creating memory leaks and masking errors. Introduce a helper routine
> that appends error messages and avoids the memory leak.

good idea, it became little messy with time ;-)
some comments below

thanks,
jirka


> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/util/parse-events.c | 102 ++++++++++++++++++++++-----------
>  tools/perf/util/parse-events.h |   2 +
>  tools/perf/util/pmu.c          |  36 ++++++------
>  3 files changed, 89 insertions(+), 51 deletions(-)
> 
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index db882f630f7e..4d42344698b8 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -182,6 +182,34 @@ static int tp_event_has_id(const char *dir_path, struct dirent *evt_dir)
>  
>  #define MAX_EVENT_LENGTH 512
>  
> +void parse_events__append_error(struct parse_events_error *err, int idx,
> +				char *str, char *help)
> +{
> +	char *new_str = NULL;
> +
> +	WARN(!str, "WARNING: failed to provide error string");

should we also bail out if str is NULL?

> +	if (err->str) {
> +		int ret;
> +
> +		if (err->help)
> +			ret = asprintf(&new_str,
> +				"%s (previous error: %s(help: %s))",
> +				str, err->str, err->help);
> +		else

please use {} for multiline condition legs

> +			ret = asprintf(&new_str,
> +				"%s (previous error: %s)",
> +				str, err->str);

does this actualy happen? could you please provide output
of this in the changelog?

> +		if (ret < 0)
> +			new_str = NULL;
> +		else
> +			zfree(&str);
> +	}
> +	err->idx = idx;
> +	free(err->str);
> +	err->str = new_str ?: str;
> +	free(err->help);
> +	err->help = help;
> +}
>  

SNIP