extern void abort(void);
void assume_abort_if_not(int cond) {
  if(!cond) {abort();}
}
extern void abort(void);
#include <assert.h>
void reach_error() { assert(0); }
extern void __VERIFIER_atomic_begin(void);
extern void __VERIFIER_atomic_end(void);

/* Testcase from Threader's distribution. For details see:
   http://www.model.in.tum.de/~popeea/research/threader
*/

#include <pthread.h>
#undef assert
#define assert(e) if (!(e)) ERROR: reach_error()

int flag1 = 0, flag2 = 0; // boolean flags
int turn; // integer variable to hold the ID of the thread whose turn is it
int x; // boolean variable to test mutual exclusion

void *thr1(void *_) {
    __VERIFIER_atomic_begin();
    flag1 = 1;
    __VERIFIER_atomic_end();
    __VERIFIER_atomic_begin();
    int f2 = flag2;
    __VERIFIER_atomic_end();
    while (f2 >= 1) {
        __VERIFIER_atomic_begin();
        int t = turn;
        __VERIFIER_atomic_end();
        if (t != 0) {
            __VERIFIER_atomic_begin();
            flag1 = 0;
            __VERIFIER_atomic_end();
            __VERIFIER_atomic_begin();
            t = turn;
            __VERIFIER_atomic_end();
            while (t != 0) {
                __VERIFIER_atomic_begin();
                t = turn;
                __VERIFIER_atomic_end();
            };
            __VERIFIER_atomic_begin();
            flag1 = 1;
            __VERIFIER_atomic_end();
        }
        __VERIFIER_atomic_begin();
        f2 = flag2;
        __VERIFIER_atomic_end();
    }
    // begin: critical section
    x = 0;
    assert(x<=0);
    // end: critical section
    __VERIFIER_atomic_begin();
    turn = 1;
    __VERIFIER_atomic_end();
    __VERIFIER_atomic_begin();
    flag1 = 0;
    __VERIFIER_atomic_end();
    return 0;
}

void *thr2(void *_) {
    __VERIFIER_atomic_begin();
    flag2 = 1;
    __VERIFIER_atomic_end();
    __VERIFIER_atomic_begin();
    int f1 = flag1;
    __VERIFIER_atomic_end();
    while (f1 >= 1) {
        __VERIFIER_atomic_begin();
        int t = turn;
        __VERIFIER_atomic_end();
        if (t != 1) {
            __VERIFIER_atomic_begin();
            flag2 = 0;
            __VERIFIER_atomic_end();
            __VERIFIER_atomic_begin();
            t = turn;
            __VERIFIER_atomic_end();
            while (t != 1) {
                __VERIFIER_atomic_begin();
                t = turn;
                __VERIFIER_atomic_end();
            };
            __VERIFIER_atomic_begin();
            flag2 = 1;
            __VERIFIER_atomic_end();
        }
        __VERIFIER_atomic_begin();
        f1 = flag1;
        __VERIFIER_atomic_end();
    }
    // begin: critical section
    x = 1;
    assert(x>=1);
    // end: critical section
    __VERIFIER_atomic_begin();
    turn = 1;
    __VERIFIER_atomic_end();
    __VERIFIER_atomic_begin();
    flag2 = 0;
    __VERIFIER_atomic_end();
    return 0;
}

int main() {
  pthread_t t1, t2;
  assume_abort_if_not(0<=turn && turn<=1);
  pthread_create(&t1, 0, thr1, 0);
  pthread_create(&t2, 0, thr2, 0);
  pthread_join(t1, 0);
  pthread_join(t2, 0);
  return 0;
}