/*

Simple example which launches two threads of execution,
but which demonstrates the perils of
accessing non-local variables from a thread.

    $ gcc -pthread two_threads_broken.c -o two_threads_broken
    $ ./two_threads_broken|more
    Hello this is thread 2: i=0
    Hello this is thread 2: i=1
    Hello this is thread 2: i=2
    Hello this is thread 2: i=3
    Hello this is thread 2: i=4
    Hello this is thread 2: i=5
    Hello this is thread 2: i=6
    Hello this is thread 2: i=7
    Hello this is thread 2: i=8
    Hello this is thread 2: i=9
    Hello this is thread 2: i=0
    Hello this is thread 2: i=1
    Hello this is thread 2: i=2
    Hello this is thread 2: i=3
    Hello this is thread 2: i=4
    Hello this is thread 2: i=5
    Hello this is thread 2: i=6
    Hello this is thread 2: i=7
    Hello this is thread 2: i=8
    Hello this is thread 2: i=9
    $...

*/

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

void *run_thread(void *argument) {
    int *p = argument;

    for (int i = 0; i < 10; i++) {
        // variable thread_number will probably have changed in main
        // before execution reaches here
        printf("Hello this is thread %d: i=%d\n", *p, i);
    }

    return NULL;
}

int main(void) {
    pthread_t thread_id1;
    int thread_number = 1;
    pthread_create(&thread_id1, NULL, run_thread, &thread_number);

    thread_number = 2;
    pthread_t thread_id2;
    pthread_create(&thread_id2, NULL, run_thread, &thread_number);

    pthread_join(thread_id1, NULL);
    pthread_join(thread_id2, NULL);
    return 0;
}