Re: [PATCH] perf tools: fix bug in usage of the basename() function

Ingo Molnar
2013-12-05T08:59:19Z

* Stephane Eranian <eranian@google.com> wrote:

>
> The basename() implementation varies a lot between systems.
> The Linux man page says: "basename may modify the content of the path,
> so it may be desirable to pass a copy when calling the function".
> On some other systems, the returned address may come from an internal
> buffer which can be reused in subsequent calls, thus the results should
> also be copied.
>
> The dso__set_basename() function was not doing this causing problems
> on some systems with wrong library names being shown by perf report,
> such as on Android systems.
>
> This patch fixes the problem.
> Thanks to Ben Cheng for tracking down the problem.
>
> Patch relative to tip.git at commit 631d5ea.
>
> Reported-by: Ben Cheng <bccheng@google.com>
> Signed-off-by: Stephane Eranian <eranian@google.com>
> ---

Just three nits:

> tools/perf/util/dso.c | 29 ++++++++++++++++++++++++++++-
> 1 file changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index af4c687c..d186ace 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -404,7 +404,34 @@ void dso__set_short_name(struct dso *dso, const char *name)
>
> static void dso__set_basename(struct dso *dso)
> {
> - dso__set_short_name(dso, basename(dso->long_name));
> + char *lname, *base;
> +
> + /*
> + * basename may modify path buffer, so we must pass
> + * a copy.

s/basename may modify path buffer
/basename() may modify the path buffer

> + */
> + lname = strdup(dso->long_name);
> + if (!lname)
> + return;
> +
> + /*
> + * basename may return pointer to internal
> + * storage which is reused in subsequent calls
> + * so copy the result
> + */

s/basename may return pointer
/basename() may return a pointer

Makes for easier reading.

(Also please use consistent periods - the first comment has a period,
the second one doesn't. ':' works well too:)

> + base = strdup(basename(lname));
> +
> + free(lname);
> +
> + if (!base)
> + return;
> +
> + if (dso->sname_alloc)
> + free((char *)dso->short_name);

That cast is probably not needed.

> + else
> + dso->sname_alloc = 1;
> +
> + dso__set_short_name(dso, base);
> }
>
> int dso__name_len(const struct dso *dso)

Otherwise:

Acked-by: Ingo Molnar <mingo@kernel.org>

Thanks,

Ingo