[lttng-dev] two tracepoints header files of one provider

[Yonghong Yan]

Thank you.

I got most. To confirm, I have two header files, each defines its own
tracepoint, they are from the same provider. The source files that use the
header files have its own #define TRACEPOINT_CREATE_PROBES and #define
TRACEPOINT_DEFINE. This won't work since two files have those defines. But
if I remove #define TRACEPOINT_CREATE_PROBES#define TRACEPOINT_DEFINE from
one of the two .c file, it should work.

tp_one.h file:

#undef TRACEPOINT_PROVIDER#define TRACEPOINT_PROVIDER hello_world
#undef TRACEPOINT_INCLUDE#define TRACEPOINT_INCLUDE "./tp_one.h"
#if !defined(_TP_ONE_H) ||
defined(TRACEPOINT_HEADER_MULTI_READ)#define _TP_ONE_H
#include <lttng/tracepoint.h>
TRACEPOINT_EVENT(
    hello_world,
    my_first_tracepoint,
    TP_ARGS(
        int, my_integer_arg,
        char*, my_string_arg
    ),
    TP_FIELDS(
        ctf_string(my_string_field, my_string_arg)
        ctf_integer(int, my_integer_field, my_integer_arg)
    ))
#endif /* _TP_ONE_H */
#include <lttng/tracepoint-event.h>


tp_one.c

#define TRACEPOINT_CREATE_PROBES#define TRACEPOINT_DEFINE
#include "tp_one.h"


tp_two.h file:

#undef TRACEPOINT_PROVIDER#define TRACEPOINT_PROVIDER hello_world
#undef TRACEPOINT_INCLUDE#define TRACEPOINT_INCLUDE "./tp_two.h"
#if !defined(_TP_TWO_H) ||
defined(TRACEPOINT_HEADER_MULTI_READ)#define _TP_TWO_H
#include <lttng/tracepoint.h>
TRACEPOINT_EVENT(
    hello_world,
    my_second_tracepoint,
    TP_ARGS(
        int, my_integer_arg,
        char*, my_string_arg
    ),
    TP_FIELDS(
        ctf_string(my_string_field, my_string_arg)
        ctf_integer(int, my_integer_field, my_integer_arg)
    ))
#endif /* _TP_TWO_H */
#include <lttng/tracepoint-event.h>


tp_two.c

#define TRACEPOINT_CREATE_PROBES#define TRACEPOINT_DEFINE
#include "tp_two.h"


hello.c
use the two tracepoints defined in the two files.

To compile (compile file one by one).

gcc -o hello tp-one.c tp-two.c hello.c -llttng-ust -ldl




On Mon, Oct 7, 2019 at 12:22 PM Mathieu Desnoyers <
mathieu.desnoyers at efficios.com> wrote:

>
>
> ----- On Oct 7, 2019, at 9:59 AM, Yonghong Yan yanyh15 at gmail.com wrote:
>
> > For lttng-ust, can I put the tracepoint definition in two files, but
> they use
> > the same provider.
>
> Based on the terminology here:
> https://lttng.org/docs/v2.10/#doc-tracing-your-own-user-application
>
> You need to have at most one instance of your tracepoint provider where
> the header is included with TRACEPOINT_CREATE_PROBES, and exactly one
> instance where TRACEPOINT_DEFINE is defined. (both can end up being within
> the same object if you wish).
>
> Then you can include your tracepoint provider header file at will across
> other compile units in your program. Just make sure none of
> TRACEPOINT_CREATE_PROBES nor TRACEPOINT_DEFINE are defined in those other
> compile units. You can therefore call tracepoints from a given probe from
> various compile units in your program.
>
> Hoping this helps clarifying things,
>
> Mathieu
>
> > Thank you.
> > Yonghong
>
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev at lists.lttng.org
> > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
>
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