On Wed, Sep 09, 2015 at 05:58:13PM -0300, Arnaldo Carvalho de Melo wrote:
SNIP
> This kind of stuff is ok, as evsel is a local variable and you kept the
> interface for perf_evsel__syscall_newtp(), i.e. it returns NULL if a new
> evsel can't be instantiated.
>
> Ok, but that is a different interface than the one used by
> perf_evsel__newtp(), that also instantiates a new evsel.
>
> So when one thinks about "foo__new()" we now need to check which one of
> the two interfaces it uses, if err.h or if the old NULL based failure
> reporting one.
>
> Double tricky if it is foo__new() and foo__new_variant(), as
> perf_evsel__syscall_newtp() and perf_evsel__newtp(), i.e. both will
> return a "struct perf_evsel" instance, but one using err.h, the other
> use NULL.
>
> Ok, you marked the ones using a comment, wonder if we couldn't use
> 'sparse' somehow here, is it used to check IS_ERR() usage in the kernel?
hum, not sure.. will check ;-)
at least we could mark related functions with __must_check
to force the return value check
>
> Ah, but what about this in trace__event_handler() in builtin-trace.c?
>
> if (evsel->tp_format) {
> event_format__fprintf(evsel->tp_format, sample->cpu,
> sample->raw_data, sample->raw_size,
> trace->output);
> }
>
>
> Don't we have to use IS_ERR() here? Ok, no, because if setting up
> evsel->tp_format fails, then that evsel will be destroyed and
> perf_evsel__newtp() will return ERR_PTR(), so it is ok not no use
> ERR_PTR(evsel->tp_format) because it will only be != NULL when it was
> successfully set up.
>
> But then, in perf_evsel__newtp_idx if zalloc() fails we will not return
> ERR_PTR(), but instead NULL, a-ha, this one seems to be a real bug, no?
hate those allocations in declarations.. never do any good ;-)
yep, NULL is not an error, so it's real bug, attached patch should fix it
thanks,
jirka
---
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 08c20ee4e27d..162973bec713 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -256,7 +256,7 @@ struct perf_evsel *perf_evsel__newtp_idx(const char *sys,
const char *name, int
perf_evsel__init(evsel, &attr, idx);
}
- return evsel;
+ return evsel ?: ERR_PTR(err);
out_free:
zfree(&evsel->name);
--
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