[lttng-dev] TP_ARGS for TRACEPOINT_EVENT_CLASS and TRACEPOINT_EVENT_INSTANCE

[Philippe Proulx]

On Thu, Dec 20, 2018 at 11:47 AM Yonghong Yan <yanyh15 at gmail.com> wrote:
>
> I am looking at the following example from lttng-ust manual. The same TP_ARGS ( ... ) are repeated in both the TRACEPOINT_EVENT_CLASS and TRACEPOINT_EVENT_INSTANCE definition. My understanding is that it actually allows using different arguments, even in this example it is the same. Am I right?

No it does not: they need to match.

See <https://github.com/lttng/lttng-ust/commit/c75c0422c64f33c0102e1778cecc812c58b700e5>.

Phil

>
> I also like the feature of having one TP_ARGS in the TRACEPOINT_EVENT_CLASS that declares the arguments for several TRACEPOINT_EVENT_INSTANCE so we do not need to have TP_ARGS in TRACEPOINT_EVENT_INSTANCE. Is that possible?
>
> Thank you
> Yonghong
>
> TRACEPOINT_EVENT_CLASS(
>     my_provider,
>     my_tracepoint_class,
>     TP_ARGS(
>         int, my_integer_arg,
>         struct app_struct *, app_struct_arg
>     ),
>     TP_FIELDS(
>         ctf_integer(int, a, my_integer_arg)
>         ctf_integer(unsigned long, b, app_struct_arg->b)
>         ctf_string(c, app_struct_arg->c)
>     )
> )
>
> TRACEPOINT_EVENT_INSTANCE(
>     my_provider,
>     my_tracepoint_class,
>     event_instance1,
>     TP_ARGS(
>         int, my_integer_arg,
>         struct app_struct *, app_struct_arg
>     )
> )
>
> TRACEPOINT_EVENT_INSTANCE(
>     my_provider,
>     my_tracepoint_class,
>     event_instance2,
>     TP_ARGS(
>         int, my_integer_arg,
>         struct app_struct *, app_struct_arg
>     )
> )
>
>
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