[ltt-dev] UST __trace_mark_tp_counter

[Nils Carlson]

On Tue, 12 Oct 2010, David Goulet wrote:

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> The register and unregister function a created with DECLARE_TRACE macro.
>
> For the test case, event_msg is a "dummy" tracepoint NOT declared to test this
> particular case where no trace declaration is done (hence the check_type
> function utility).

Ok, though I'm not sure I understand you? What do you end up checking by 
not declaring the tracepoint? As everything compiles anyway?

I don't really like that compiling fails with -O0 and succeeds with -O2, 
it's not really pleasing to my sense of order... :-)

> David
>
> On 10-10-12 10:27 AM, Nils Carlson wrote:
>> I was doing some minor fixes in UST today when I came across a small
>> phenomenon. Since including Davids testcase for trae_mark_tp I cannot
>> compile with -Wall. The compiler throws out a
>>
>> tracepoint_test.o: In function `__check_tp_type':
>> /home/nils/devel/ust/tests/tracepoint/tracepoint_test.c:64: undefined
>> reference to `register_trace_ust_event_msg'
>> collect2: ld returned 1 exit status
>>
>>
>> Looking at the macros in include/ust/marker.h I find the function
>>
>> void __check_tp_type(void)                \
>>         {                            \
>>             register_trace_##tp_name(tp_cb, call_private); \
>>         }                            \
>>
>> defined inside the __trace_mark_tp_counter function.
>>
>> In the case of _DEFINE_MARKER_TP we don't create the register and
>> unregister functions as far as I can tell. And the error only occurs
>> when compiling with -Wall which I'm guessing is because __check_tp_type
>> is never called and is optimised out completely normally? If I create a
>> void pointer and assign the function address to it I get the error when
>> compiling without -Wall as well.
>>
>> Mathieu: What do you think of this, does it seem reasonable? How do you
>> think we should fix it? Simplest would be to remove the check, I don't
>> know if the register and unregister functions will be used for anything?
>>
>> /Nils
>
> - --
> David Goulet
> LTTng project, DORSAL Lab.
>
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