Proactive tracing

First, one process must register itself as the designated trace-logging process by issuing the _NTO_TRACE_LOGGER_ATTACH command. This command has start_ev and stop_ev parameters, which can be NULL or pointers to sigevents that are to be delivered when tracing starts and stops:

TraceEvent(_NTO_TRACE_LOGGER_ATTACH, start_ev, stop_ev);

Then, the following simple call would inject the integer values of eventcode, first, and second into the event stream:

TraceEvent(_NTO_TRACE_INSERTSUSEREVENT, eventcode, first, second);

You could also inject a string event (e.g., My Event) into the event stream, as shown in the following code:

#include <stdio.h>
#include <sys/trace.h>

/* Code to associate with emitted events */
#define MYEVENTCODE 12

int main(int argc, char **argv) {
    printf("My pid is %d \n", getpid());

    /* Inject two integer events (26, 1975) */
    TraceEvent(_NTO_TRACE_INSERTSUSEREVENT, MYEVENTCODE, 26, 1975);

    /* Inject a string event (My Event) */
    TraceEvent(_NTO_TRACE_INSERTUSRSTREVENT, MYEVENTCODE, "My Event");

    return 0;
}

The output, as gathered by the traceprinter data interpreter, would look something like this:

.
.
.
t:0x38ea737e CPU:00 USREVENT:EVENT:12, d0:26 d1:1975
.
.
.
t:0x38ea7cb0 CPU:00 USREVENT:EVENT:12 STR:"My Event"