What's the real order? Order in which friend threads were spawned or the ticket id that they came back with?

friends.c

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

static int ticketid = 0;
pthread_mutex_t lock;

// buyticket function remote dial a central store to obtain ticket id
void * buyticket() {
    int *id = (int *)malloc(sizeof(int));
    pthread_mutex_lock(&lock);
    *id = ticketid++;
    pthread_mutex_unlock(&lock);
    return id;
}

void * friend(void *arg) {
    return buyticket();
}

int main() {
    // N friends one by one to go buy ticket
    int N = 10;
    int i;
    pthread_t friends[N];
    for (i=0; i<N; i++) {
        // imagine spawn of thread as u saying to friends on Node A, B, C ... to buy a ticket in order
        pthread_create(&friends[i], NULL, friend, NULL);
    }

    // wait for friends to come back
    int *id;
    for (i=0; i<N; i++) {
        pthread_join(friends[i], (void **)&id);
        printf("friend id %d, ticket id %d\n", i, *id);
        free(id);
    }
}

This code is not to say that above strategy is correct, but more to imply that how ordering of operations are simply lost as soon as you start to multi-thread the client side.