#include <stdio.h>
#include <pthread.h>
#include <unistd.h>

double * px = NULL;

static pthread_mutex_t  mutex = PTHREAD_MUTEX_INITIALIZER;

void * fn_thread (void * p_int) {
    for (int i = 0; i < *(int *) p_int; ++i) {
        pthread_mutex_lock(& mutex);
        printf("%f\n", *px);
        pthread_mutex_unlock(& mutex);
    }
    pthread_exit(0);
}

int main () {
    int max = 0;
    pthread_t p1;

    printf("Saisir max : \n");
    scanf ("%d", &max);
    printf("Ok ! \n");

    double x = 1.0;
    px = &x;
    pthread_create (& p1, NULL, fn_thread, (void *) &max);

    for (int i = 0; i < max; ++i) {
        pthread_mutex_lock(& mutex);
        px = NULL;
        printf("i : %d\n", i);
        px = &x;
        pthread_mutex_unlock(& mutex);
    }

    pthread_join(p1, NULL);

    return 0;
}