# setjmp

***

**1. Error Handling**

```cpp
int main() {
  jmp_buf env;
  if (setjmp(env) != 0) {
    // An error occurred, handle it
    return 1;
  }

  // Do something that might throw an error

  return 0;
}
```

**2. Non-Local Return**

```cpp
int func1() {
  jmp_buf env;
  setjmp(env);
  return 1;  // This return will jump back to the caller of func1
}

int main() {
  int ret = func1();
  printf("func1 returned %d\n", ret);
  return 0;
}
```

**3. Fork with Longjmp**

```cpp
int main() {
  jmp_buf env;
  setjmp(env);

  pid_t child_pid = fork();
  if (child_pid == 0) {
    // Child process
    longjmp(env, 1);
  } else {
    // Parent process
    printf("Child process returned %d\n", waitpid(child_pid, NULL, 0));
  }

  return 0;
}
```

**4. Signal Handling**

```cpp
void signal_handler(int signum) {
  longjmp(env, signum);
}

int main() {
  jmp_buf env;
  setjmp(env);
  signal(SIGINT, signal_handler);

  // Do something that might be interrupted by a signal

  return 0;
}
```

**5. Thread Creation**

```cpp
void *thread_function(void *arg) {
  jmp_buf env;
  setjmp(env);

  // Do something in the thread

  longjmp(env, 1);
  return NULL;
}

int main() {
  pthread_t thread;
  pthread_create(&thread, NULL, thread_function, NULL);

  int ret = pthread_join(thread, NULL);
  printf("Thread returned %d\n", ret);

  return 0;
}
```

**6. Exception Handling**

```cpp
class MyException {
public:
  int code;
  MyException(int code) : code(code) {}
};

void try_block() {
  try {
    // Do something that might throw an exception
  } catch (const MyException &e) {
    longjmp(env, e.code);
  }
}

int main() {
  jmp_buf env;
  setjmp(env);
  try_block();

  return 0;
}
```

**7. Coroutines**

```cpp
void coroutine_function() {
  while (true) {
    // Yield to the caller
    if (!setjmp(env)) {
      // Do something in the coroutine
    } else {
      // Return from the coroutine
      break;
    }
  }
}

int main() {
  jmp_buf env;
  coroutine_function();

  return 0;
}
```

**8. Asynchronous Programming**

```cpp
void asynchronous_function(void *arg) {
  jmp_buf env;
  setjmp(env);

  // Perform asynchronous operation

  longjmp(env, 1);
}

int main() {
  jmp_buf env;
  setjmp(env);

  pthread_t thread;
  pthread_create(&thread, NULL, asynchronous_function, NULL);

  int ret = pthread_join(thread, NULL);
  printf("Asynchronous function returned %d\n", ret);

  return 0;
}
```

**9. Timeouts**

```cpp
void timeout_function() {
  alarm(1);  // Set a timeout of 1 second

  while (true) {
    // Do something in the timeout function
    if (setjmp(env) != 0) {
      // Timeout occurred
      break;
    }
  }
}

int main() {
  jmp_buf env;
  timeout_function();

  return 0;
}
```

**10. State Machines**

```cpp
enum State { START, PROCESS, DONE };

void state_machine_function() {
  State state = START;

  while (true) {
    switch (state) {
      case START:
        // Do something in the START state
        state = PROCESS;
        break;
      case PROCESS:
        // Do something in the PROCESS state
        state = DONE;
        break;
      case DONE:
        // Do something in the DONE state
        state = START;
        break;
    }

    if (setjmp(env) != 0) {
      // Exit from the state machine
      break;
    }
  }
}

int main() {
  jmp_buf env;
  state_machine_function();

  return 0;
}
```

**11. Emulated Threads**

```cpp
struct thread_struct {
  pthread_t thread_id;
  jmp_buf env;
};

void *thread_function(void *arg) {
  thread_struct *thread = (thread_struct *)arg;

  // Do something in the thread

  longjmp(thread->env, 1);
  return NULL;
}

int main() {
  thread_struct threads[10];

  for (int i = 0; i < 10; i++) {
    pthread_create(&threads[i].thread_id, NULL, thread_function, &threads[i]);
  }

  for (int i = 0; i < 10; i++) {
    int ret = pthread_join(threads[i].thread_id, NULL);
    printf("Thread %d returned %d\n", i, ret);
  }

  return 0;
}
```

**12. Context-Switching**

```cpp
struct context {
  jmp_buf env;
  int data;
};

void context_switch(context *from, context *to) {
  if (setjmp(from->env) == 0) {
    // Save the current context and switch to the new context
    memcpy(&to->env, &from->env, sizeof(jmp_buf));
    longjmp(to->env, 1);
  } else {
    // Restore the previous context
    memcpy(&from->env, &to->env, sizeof(jmp_buf));
  }
}

int main() {
  context context1, context2;

  context1.data = 1;
  context2.data = 2;

  while (true) {
    printf("Context1: %d\n", context1.data);
    context_switch(&context1, &context2);

    printf("Context2: %d\n", context2.data);
    context_switch(&context2, &context1);
  }

  return 0;
}
```

**13. Co-Routines with Go Style**

```cpp
struct goroutine {
  jmp_buf env;
  int data;
};

void goroutine_main(goroutine *g) {
  while (true) {
    if (setjmp(g->env) == 0) {
      // Yield to the caller
    } else {
      // Return from the goroutine
      break;
    }
  }
}

int main() {
  goroutine g;

  g.data = 1;
  goroutine_main(&g);

  return 0;
}
```

**14. Exception Unwinding**

```cpp
void foo() {
  try {
    // Do something that might throw an exception
  } catch (const exception &e) {
    // Unwind the stack using setjmp and longjmp
    longjmp(env, 1);
  }
}

int main() {
  jmp_buf env;
  setjmp(env);
  foo();

  return 0;
}
```

**15. Error Recovery**

```cpp
int foo() {
  if (setjmp(env) != 0) {
    return -1;  // An error occurred, recover from it
  }

  // Do something that might return an error code

  // No error occurred
  return 0;
}

int main() {
  int ret = foo();
  if (ret != 0) {
    // Handle the error
  }

  return 0;
}
```

**16. Non-Local GoTo**

```cpp
void foo() {
  if (setjmp(env) == 0) {
    // Do something
    goto label;  // Jump to the label
  }

label:
  // Continue execution after the goto
}

int main() {
  foo();
  return 0;
}
```

**17. Task Management**

```cpp
struct task {
  jmp_buf env;
  int data;
};

void task_main(task *t) {
  while (true) {
    if (setjmp(t->env) == 0) {
      // Yield to the caller
    } else {
      // Return from the task
      break;
    }
  }
}

int main() {
  task t;

  t.data = 1;
  task_main(&t);

  return 0;
}
```

**18. Event-Driven Programming**

```cpp
struct event {
  int type;
  void *data;
};

void event_loop() {
  while (true) {
    event e;

    // Get the next event

    switch (e.type) {
      case EVENT_TYPE_A:
        // Handle event type A
        break;
      case EVENT_TYPE_B:
        // Handle event type B
        break;
      case EVENT_TYPE_C:
        // Handle event type C
        break;
    }
  }
}

int main() {
  event_loop();
  return 0;
}
```

**19. Dynamic Control Flow**

```cpp
int main() {
  jmp_buf env;
  setjmp(env);

  int choice = 1;

  while (true) {
    switch (choice) {
      case 1:
        // Do something for choice 1
        choice = 2;
        break;
      case 2:
        // Do something for choice 2
        choice = 3;
        break;
      case 3:
        // Do something for choice 3
        choice = 1;
        break;
      default:
        longjmp(env, 1);  // Exit from the loop
        break;
    }
  }

  return 0;
}
```

**20. Recursive Descent Parsing**

```cpp
void parse_expression() {
  if (setjmp(env) == 0) {
    // Parse the expression recursively
  } else {
    // The expression is not valid, handle the error
  }
}

int main() {
  parse_expression();
  return 0;
}
```

**21. Emulated Exceptions**

```cpp
struct exception {
  int code;
  const char *message;
};

void throw_exception(const exception &e) {
  longjmp(env, e.code);
}

int main() {
  jmp_buf env;
  setjmp(env);

  try {
    // Do something that might throw an exception
  } catch (const exception &e) {
    // Handle the exception
    printf("Exception occurred: %s\n", e.message);
  }

  return 0;
}
```

**22. Cooperative Multi-Tasking**

```cpp
struct task {
  jmp_buf env;
  void (*func)(void *);
  void *arg;
};

void task_main(task *t) {
  t->func(t->arg);
  longjmp(t->env, 1);  // Exit from the task
}

int main() {
  task t1, t2;

  t1.func = task1_func;
  t1.arg = (void *)1;
  t2.func = task2_func;
  t2.arg = (void *)2;

  while (true) {
    task_main(&t1);
    task_main(&t2);
  }

  return 0;
}
```

**23. Error Handling in Multi-Threaded Applications**

```cpp
void thread_function(void *arg) {
  jmp_buf env;
  setjmp(env);

  // Do something that might throw an error
  longjmp(env, 1);
}

int main() {
  jmp_buf env;
  setjmp(env);

  pthread_t thread;
  pthread_create(&thread, NULL, thread_function, NULL);

  int ret = pthread_join(thread, NULL);
  if (ret != 0) {
    // Handle the error
  }

  return 0;
}
```

**24. Dynamic Code Execution**

```cpp
int main() {
  jmp_buf env;
  setjmp(env);

  char code[] = "printf(\"Hello, world!\n\");";

  void (*func)() = NULL;
  func = (void (*)())dlopen(code, RTLD_NOW);  // Dynamically load the code

  func();  // Execute the code
  dlclose(func);  // Unload the code

  return 0;
}
```

**25. Memory Protection**

```cpp
void protected_function() {
  jmp_buf env;
  setjmp(env);

  // Do something that might access invalid memory
  longjmp(env, 1);
}

int main() {
  jmp_buf env;
  setjmp(env);
  protected_function();

  return 0;
}
```

**26. Deadlock Recovery**

```cpp
void thread1_function(void *arg) {
  jmp_buf env;
  setjmp(env);

  // Acquire lock 1
  if (setjmp(env) != 0) {
    // Deadlock occurred, recover from it
  }

  // Acquire lock 2

  // Release lock 1
  // Release lock 2
}

void thread2_function(void *arg) {
  jmp_buf env;
  setjmp(env);

  // Acquire lock 2
  if (setjmp(env) != 0) {
    // Deadlock occurred, recover from it
  }

  // Acquire lock 1

  // Release lock 2
  // Release lock 1
}

int main() {
  jmp_buf env;
  setjmp(env);

  pthread_t thread1, thread2;
  pthread_create(&thread1, NULL, thread1_function, NULL);
  pthread_create(&thread2, NULL, thread2_function, NULL);

  int ret1 = pthread_join(thread1, NULL);
  int ret2 = pthread_join(thread2, NULL);

  if (ret1 != 0 || ret2 != 0) {
    // Deadlock occurred, handle it
  }

  return 0;
}
```

**27. Error Propagation**

```cpp
int foo() {
  jmp_buf env;
  int ret = setjmp(env);
  if (ret == 0) {
    // Do something that might throw an error
    longjmp(env, 1);
  } else {
    // Error occurred, handle it
    return -1;
  }
}

int main() {
  int ret = foo();
  if (ret != 0) {
    // Handle the error
  }

  return 0;
}
```

**28. Lightweight Threading**

```cpp
struct thread {
  jmp_buf env;
  void (*func)(void *);
  void *arg;
};

void thread_main(thread *t) {
  t->func(t->arg);
  longjmp(t->env, 1);  // Exit from the thread
}

int main() {
  thread t;

  t.func = thread_function;
  t.arg = (void *)1;

  while (true) {
    thread_main(&t);
  }

  return 0;
}
```

**29. Thread Synchronization**

```cpp
struct mutex {
  jmp_buf env;
  int locked;
};

void mutex_lock(mutex *m) {
  if (setjmp(m->env) == 0) {
    // Acquire the mutex
    m->locked = 1;
  } else {
    // The mutex is already locked, wait for it to be unlocked
  }
}

void mutex_unlock(mutex *m) {
  m->locked = 0;
  longjmp(m->env, 1);  // Unblock any waiting threads
}

int main() {
  mutex m;
  m.locked = 0;

  // Thread 1: Acquire and release the mutex
  mutex_lock(&m);
  // Do something
  mutex_unlock(&m);

  // Thread 2: Acquire and release the mutex
  mutex_lock(&m);
  // Do something
  mutex_unlock(&m);

  return 0;
}
```

**30. Failure Injection**

```cpp
void test_function() {
  jmp_buf env;
  setjmp(env);

  // Do something that might fail
  longjmp(env, 1);  // Inject a failure
}

int main() {
  jmp_buf env;
  setjmp(env);

  test_function();

  return 0;
}
```

**31. Rollback Transactions**

```cpp
struct transaction {
  jmp_buf env;
  int state;
};

void transaction_start(transaction *t) {
  if (setjmp(t->env) == 0) {
    // Start the transaction
    t->state = 1;
  } else {
    // The transaction has already started, abort it
  }
}

void transaction_commit(transaction *t) {
  t->state = 2;
  longjmp(t->env, 1);  // Commit the transaction
}

void transaction_abort(transaction *t) {
  t->state = 3;
  longjmp(t->env, 1);  // Abort the transaction
}

int main() {
  transaction t;
  t.state = 0;

  transaction_start(&t);
  // Do something in the transaction
  transaction_commit(&t);

  return 0;
}
```

**32. Lazy Evaluation**

```cpp
void lazy_function() {
  jmp_buf env;
  setjmp(env);

  // Do something that is not essential
  longjmp(env, 1);  // Mark the function as evaluated
}

int main() {
  jmp_buf env;
  setjmp(env);

  // Call the lazy function if it has not been evaluated yet
  if (setjmp(env) == 0) {
    lazy_function();
  }

  return 0;
}
```

**33. Profiling**

```cpp
void profiled_function() {
  jmp_buf env;
  setjmp(env);

  // Do something that needs to be profiled
  longjmp(env, 1);  // Mark the function as profiled
}

int main() {
  jmp_buf env;
  setjmp(env);

  // Call the profiled function
  profil

```