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

int max;
// WOW, new word: it means the compiler is not allowed to optimize this varible
volatile int counter = 0;

void* mythread(void* arg) {
    char* letter = arg;
    int i;

    printf("%s: begin [addr of i: %p]\n", letter, (void*) &i);

    for (i = 0; i < max; i++) {
        counter = counter + 1;
    }

    printf("%s: done with counter at %d\n", letter, counter);
    return NULL;
}

int main(int argc, char* argv[]) {
    if (argc != 2) {
        fprintf(stderr, "usage: main-first <loopcount>\n");
        exit(1);
    }
    max = atoi(argv[1]);

    pthread_t p1, p2;
    printf("main: begin [counter = %d] [%x]\n", counter,
           *(unsigned int*)&counter);

    pthread_create(&p1, NULL, mythread, "A");
    pthread_create(&p2, NULL, mythread, "B");

    pthread_join(p1, NULL);
    pthread_join(p2, NULL);

    printf("main: done\n [counter: %d]\n [should: %d]\n", counter, max * 2);
    return 0;
}