text: // RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
  // UNSUPPORTED: tvos, watchos
  // XFAIL: ios && !iossim
  #include "sanitizer_common/sanitizer_ucontext.h"
  #include "test.h"
  
  char stack[64 * 1024] __attribute__((aligned(16)));
  
  ucontext_t uc, orig_uc[2];
  void *fiber, *orig_fiber[2];
  
  const unsigned N = 1000;
  
  __attribute__((noinline))
  void switch0() {
    __tsan_switch_to_fiber(orig_fiber[0], 0);
    swapcontext(&uc, &orig_uc[0]);
  }
  
  void func() {
    for (;;) {
      switch0();
      __tsan_switch_to_fiber(orig_fiber[1], 0);
      swapcontext(&uc, &orig_uc[1]);
    }
  }
  
  void *Thread(void *x) {
    orig_fiber[1] = __tsan_get_current_fiber();
    for (unsigned i = 0; i < N; i++) {
      barrier_wait(&barrier);
      __tsan_switch_to_fiber(fiber, 0);
      swapcontext(&orig_uc[1], &uc);
      barrier_wait(&barrier);
    }
    return 0;
  }
  
  int main() {
    fiber = __tsan_create_fiber(0);
    barrier_init(&barrier, 2);
    pthread_t t;
    pthread_create(&t, 0, Thread, 0);
    orig_fiber[0] = __tsan_get_current_fiber();
    getcontext(&uc);
    uc.uc_stack.ss_sp = stack;
    uc.uc_stack.ss_size = sizeof(stack);
    uc.uc_link = 0;
    makecontext(&uc, func, 0);
    for (unsigned i = 0; i < N; i++) {
      __tsan_switch_to_fiber(fiber, 0);
      swapcontext(&orig_uc[0], &uc);
      barrier_wait(&barrier);
      barrier_wait(&barrier);
    }
    pthread_join(t, 0);
    __tsan_destroy_fiber(fiber);
    fprintf(stderr, "PASS\n");
    return 0;
  }
  
  // CHECK-NOT: WARNING: ThreadSanitizer:
  // CHECK: PASS
  