app.c

#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include <link.h>

static void *lib_truc = NULL;
static int (*func_ptr) (int a) = NULL;

static void* load_lib(char *name) {

    void *handle;
    struct link_map *lm;

    handle = dlopen(name, RTLD_NOW);
    if (!handle) {
        printf("Can't load %s: %s\n", name, dlerror());
        abort();
    }

    lm = handle;
    printf("lib %s is loaded at 0x%lx\n", name, lm->l_addr);

    return handle;
}

static void* lookup_sym(void *lib, char *sym) {
    char *error;
    void *ret;
     // First, clear the error flag.
    dlerror();

    ret = dlsym(lib, sym);
    error = dlerror();
    if (error) {
        printf("Can't lookup %s: %s\n", sym, error);
        abort();
    }

    return ret;
}


int main() {
    int result;

    lib_truc = load_lib("./libtruc.so");
    func_ptr = lookup_sym(lib_truc, "func");

    result = func_ptr(4);

    printf("Result is %d\n", result);

    dlclose(lib_truc);

    return 0;
}

Makefile

all: libtruc.so app tracepoints.so

app: app.o
	gcc -o app app.o -ldl
app.o: app.c
	gcc -c app.c -g3 -O0 -Wall


libtruc.so: truc.o tracepoints.o
	gcc -shared -o libtruc.so truc.o -ldl
truc.o: truc.c
	gcc -c truc.c -g3 -O0 -Wall -fPIC
tracepoints.o: tracepoints.c
	gcc -c tracepoints.c -I. -fPIC
tracepoints.so: tracepoints.o
	gcc -shared -Wl,--no-as-needed -o $@ -llttng-ust $<

clean:
	rm -f *.o *.so app

tracepoints.c

#define TRACEPOINT_CREATE_PROBES
/*
 * The header containing our TRACEPOINT_EVENTs.
 */
#include "tracepoints.h"

tracepoints.h

#undef TRACEPOINT_PROVIDER
#define TRACEPOINT_PROVIDER sample_tracepoint

#undef TRACEPOINT_INCLUDE
#define TRACEPOINT_INCLUDE "./tracepoints.h"

#if !defined(TRACEPOINTS_H) || defined(TRACEPOINT_HEADER_MULTI_READ)
#define TRACEPOINTS_H

#include <lttng/tracepoint.h>

TRACEPOINT_EVENT(
    sample_tracepoint,
    message,
    TP_ARGS(int, voila),
    TP_FIELDS(
        ctf_integer(int, intfield, voila)
    )
)

#endif /* TRACEPOINTS_H */

#include <lttng/tracepoint-event.h>

truc.c

#define TRACEPOINT_DEFINE
#define TRACEPOINT_PROBE_DYNAMIC_LINKAGE

#include "truc.h"
#include "tracepoints.h"

int func(int a) {
    tracepoint(sample_tracepoint, message, a);
    return a + 1;
}

truc.h

int func(int a);