sdk/runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

// This file contains test functions for the dart:ffi test cases.

#include <stddef.h>
#include <stdlib.h>
#include <sys/types.h>
#include <csignal>
#include <cstdio>
#include <cstdlib>
#include <cstring>

#include "platform/globals.h"
#include "platform/memory_sanitizer.h"
#if defined(DART_HOST_OS_WINDOWS)
#include <psapi.h>
#include <windows.h>
#else
#include <unistd.h>
#endif

// Only OK to use here because this is test code.
#include <condition_variable>  // NOLINT(build/c++11)
#include <functional>          // NOLINT(build/c++11)
#include <mutex>               // NOLINT(build/c++11)
#include <queue>               // NOLINT(build/c++11)
#include <thread>              // NOLINT(build/c++11)

#include <setjmp.h>  // NOLINT
#include <signal.h>  // NOLINT
#include <iostream>
#include <limits>

// TODO(dartbug.com/40579): This requires static linking to either link
// dart.exe or dartaotruntime.exe on Windows.
// The sample currently fails on Windows in AOT mode.
#include "include/dart_api.h"
#include "include/dart_native_api.h"

#include "include/dart_api_dl.h"

namespace dart {

#define CHECK(X)                                                               \
  if (!(X)) {                                                                  \
    fprintf(stderr, "%s\n", "Check failed: " #X);                              \
    return 1;                                                                  \
  }

#define CHECK_EQ(X, Y) CHECK((X) == (Y))

#define ENSURE(X)                                                              \
  if (!(X)) {                                                                  \
    fprintf(stderr, "%s:%d: %s\n", __FILE__, __LINE__, "Check failed: " #X);   \
    exit(1);                                                                   \
  }

////////////////////////////////////////////////////////////////////////////////
// Functions for stress-testing.

DART_EXPORT int64_t MinInt64() {
  Dart_ExecuteInternalCommand("gc-on-nth-allocation",
                              reinterpret_cast<void*>(1));
  return 0x8000000000000000;
}

DART_EXPORT int64_t MinInt32() {
  Dart_ExecuteInternalCommand("gc-on-nth-allocation",
                              reinterpret_cast<void*>(1));
  return 0x80000000;
}

DART_EXPORT double SmallDouble() {
  Dart_ExecuteInternalCommand("gc-on-nth-allocation",
                              reinterpret_cast<void*>(1));
  return 0x80000000 * -1.0;
}

// Requires boxing on 32-bit and 64-bit systems, even if the top 32-bits are
// truncated.
DART_EXPORT void* LargePointer() {
  Dart_ExecuteInternalCommand("gc-on-nth-allocation",
                              reinterpret_cast<void*>(1));
  uint64_t origin = 0x8100000082000000;
  return reinterpret_cast<void*>(origin);
}

DART_EXPORT void TriggerGC(uint64_t count) {
  Dart_ExecuteInternalCommand("gc-now", nullptr);
}

DART_EXPORT void CollectOnNthAllocation(intptr_t num_allocations) {
  Dart_ExecuteInternalCommand("gc-on-nth-allocation",
                              reinterpret_cast<void*>(num_allocations));
}

// Triggers GC. Has 11 dummy arguments as unboxed odd integers which should be
// ignored by GC.
DART_EXPORT void Regress37069(uint64_t a,
                              uint64_t b,
                              uint64_t c,
                              uint64_t d,
                              uint64_t e,
                              uint64_t f,
                              uint64_t g,
                              uint64_t h,
                              uint64_t i,
                              uint64_t j,
                              uint64_t k) {
  Dart_ExecuteInternalCommand("gc-now", nullptr);
}

DART_EXPORT uint8_t IsThreadInGenerated() {
  return Dart_ExecuteInternalCommand("is-thread-in-generated", nullptr) !=
                 nullptr
             ? 1
             : 0;
}

#if !defined(DART_HOST_OS_WINDOWS)
DART_EXPORT void* UnprotectCodeOtherThread(void* isolate,
                                           std::condition_variable* var,
                                           std::mutex* mut) {
  std::function<void()> callback = [&]() {
    mut->lock();
    var->notify_all();
    mut->unlock();

    // Wait for mutator thread to continue (and block) before leaving the
    // safepoint.
    while (Dart_ExecuteInternalCommand("is-mutator-in-native", isolate) !=
           nullptr) {
      usleep(10 * 1000 /*10 ms*/);
    }
  };

  struct {
    void* isolate;
    std::function<void()>* callback;
  } args = {.isolate = isolate, .callback = &callback};

  Dart_ExecuteInternalCommand("run-in-safepoint-and-rw-code", &args);
  return nullptr;
}

struct HelperThreadState {
  std::mutex mutex;
  std::condition_variable cvar;
  std::unique_ptr<std::thread> helper;
};

DART_EXPORT void* TestUnprotectCode(void (*fn)(void*)) {
  HelperThreadState* state = new HelperThreadState;

  {
    std::unique_lock<std::mutex> lock(state->mutex);  // locks the mutex
    state->helper.reset(new std::thread(UnprotectCodeOtherThread,
                                        Dart_CurrentIsolate(), &state->cvar,
                                        &state->mutex));

    state->cvar.wait(lock);
  }

  if (fn != nullptr) {
    fn(state);
    return nullptr;
  } else {
    return state;
  }
}

DART_EXPORT void WaitForHelper(HelperThreadState* helper) {
  helper->helper->join();
  delete helper;
}
#else
// Our version of VSC++ doesn't support std::thread yet.
DART_EXPORT void WaitForHelper(void* helper) {}
DART_EXPORT void* TestUnprotectCode(void (*fn)(void)) {
  return nullptr;
}
#endif

// Defined in ffi_test_functions.S.
//
// Clobbers some registers with special meaning in Dart before re-entry, for
// stress-testing. Not used on 32-bit Windows due to complications with Windows
// "safeseh".
// TODO(47824): Figure out how ARM/ARM64 syntax is different on Windows.
#if defined(DART_TARGET_OS_WINDOWS) &&                                         \
    (defined(HOST_ARCH_IA32) || defined(HOST_ARCH_ARM) ||                      \
     defined(HOST_ARCH_ARM64))
void ClobberAndCall(void (*fn)()) {
  fn();
}
#else
extern "C" void ClobberAndCall(void (*fn)());
#endif

DART_EXPORT intptr_t TestGC(void (*do_gc)()) {
  ClobberAndCall(do_gc);
  return 0;
}

struct CallbackTestData {
  intptr_t success;
  void (*callback)();
};

#if defined(DART_TARGET_OS_LINUX)

thread_local sigjmp_buf buf;
void CallbackTestSignalHandler(int) {
  siglongjmp(buf, 1);
}

intptr_t ExpectAbort(void (*fn)()) {
  fprintf(stderr, "**** EXPECT STACKTRACE TO FOLLOW. THIS IS OK. ****\n");

  struct sigaction old_action = {};
  intptr_t result = sigsetjmp(buf, /*savesigs=*/1);
  if (result == 0) {
    // Install signal handler.
    struct sigaction handler = {};
    handler.sa_handler = CallbackTestSignalHandler;
    sigemptyset(&handler.sa_mask);
    handler.sa_flags = 0;

    sigaction(SIGABRT, &handler, &old_action);

    fn();
  } else {
    // Caught the setjmp.
    sigaction(SIGABRT, &old_action, nullptr);
    exit(0);
  }
  fprintf(stderr, "Expected abort!!!\n");
  exit(1);
}

void* TestCallbackOnThreadOutsideIsolate(void* parameter) {
  CallbackTestData* data = reinterpret_cast<CallbackTestData*>(parameter);
  data->success = ExpectAbort(data->callback);
  return nullptr;
}

intptr_t TestCallbackOtherThreadHelper(void* (*tester)(void*), void (*fn)()) {
  CallbackTestData data = {1, fn};
  pthread_attr_t attr;
  intptr_t result = pthread_attr_init(&attr);
  CHECK_EQ(result, 0);

  pthread_t tid;
  result = pthread_create(&tid, &attr, tester, &data);
  CHECK_EQ(result, 0);

  result = pthread_attr_destroy(&attr);
  CHECK_EQ(result, 0);

  void* retval;
  result = pthread_join(tid, &retval);

  // Doesn't actually return because the other thread will exit when the test is
  // finished.
  return 1;
}

// Run a callback on another thread and verify that it triggers SIGABRT.
DART_EXPORT intptr_t TestCallbackWrongThread(void (*fn)()) {
  return TestCallbackOtherThreadHelper(&TestCallbackOnThreadOutsideIsolate, fn);
}

// Verify that we get SIGABRT when invoking a native callback outside an
// isolate.
DART_EXPORT intptr_t TestCallbackOutsideIsolate(void (*fn)()) {
  Dart_Isolate current = Dart_CurrentIsolate();

  Dart_ExitIsolate();
  CallbackTestData data = {1, fn};
  TestCallbackOnThreadOutsideIsolate(&data);
  Dart_EnterIsolate(current);

  return data.success;
}

DART_EXPORT intptr_t TestCallbackWrongIsolate(void (*fn)()) {
  return ExpectAbort(fn);
}

DART_EXPORT intptr_t TestCallbackLeaf(void (*fn)()) {
#if defined(DEBUG)
  // Calling a callback from a leaf call will crash when trying to leave the
  // safepoint.
  return ExpectAbort(fn);
#else
  // The above will only crash in debug as ASSERTS are disabled in all other
  // build modes.
  return 0;
#endif
}

void CallDebugName() {
  Dart_DebugName();
}

DART_EXPORT intptr_t TestLeafCallApi(void (*fn)()) {
  // This should be fine since it's a simple function that returns a const
  // string. Though any API call should be considered unsafe from leaf calls.
  Dart_VersionString();
#if defined(DEBUG)
  // This will fail because it requires running in DARTSCOPE.
  return ExpectAbort(&CallDebugName);
#else
  // The above will only crash in debug as ASSERTS are disabled in all other
  // build modes.
  return 0;
#endif
}

#endif  // defined(DART_TARGET_OS_LINUX)

// Restore default SIGPIPE handler, which is only needed on mac
// since that is the only platform we explicitly ignore it.
// See Platform::Initialize() in platform_macos.cc.
DART_EXPORT void RestoreSIGPIPEHandler() {
#if defined(DART_HOST_OS_MACOS)
  signal(SIGPIPE, SIG_DFL);
#endif
}

DART_EXPORT void IGH_MsanUnpoison(void* start, intptr_t length) {
  MSAN_UNPOISON(start, length);
}

DART_EXPORT Dart_Isolate IGH_CreateIsolate(const char* name, void* peer) {
  struct Helper {
    static void ShutdownCallback(void* ig_data, void* isolate_data) {
      char* string = reinterpret_cast<char*>(isolate_data);
      ENSURE(string[0] == 'a');
      string[0] = 'x';
    }
    static void CleanupCallback(void* ig_data, void* isolate_data) {
      char* string = reinterpret_cast<char*>(isolate_data);
      ENSURE(string[2] == 'c');
      string[2] = 'z';
    }
  };

  Dart_Isolate parent = Dart_CurrentIsolate();
  Dart_ExitIsolate();

  char* error = nullptr;
  Dart_Isolate child =
      Dart_CreateIsolateInGroup(parent, name, &Helper::ShutdownCallback,
                                &Helper::CleanupCallback, peer, &error);
  if (child == nullptr) {
    Dart_EnterIsolate(parent);
    Dart_Handle error_obj = Dart_NewStringFromCString(error);
    free(error);
    Dart_ThrowException(error_obj);
    return nullptr;
  }
  Dart_ExitIsolate();
  Dart_EnterIsolate(parent);
  return child;
}

DART_EXPORT void IGH_StartIsolate(Dart_Isolate child_isolate,
                                  int64_t main_isolate_port,
                                  const char* library_uri,
                                  const char* function_name,
                                  bool errors_are_fatal,
                                  Dart_Port on_error_port,
                                  Dart_Port on_exit_port) {
  Dart_Isolate parent = Dart_CurrentIsolate();
  Dart_ExitIsolate();
  Dart_EnterIsolate(child_isolate);
  {
    Dart_EnterScope();

    Dart_Handle library_name = Dart_NewStringFromCString(library_uri);
    ENSURE(!Dart_IsError(library_name));

    Dart_Handle library = Dart_LookupLibrary(library_name);
    ENSURE(!Dart_IsError(library));

    Dart_Handle fun = Dart_NewStringFromCString(function_name);
    ENSURE(!Dart_IsError(fun));

    Dart_Handle port = Dart_NewInteger(main_isolate_port);
    ENSURE(!Dart_IsError(port));

    Dart_Handle args[] = {
        port,
    };

    Dart_Handle result = Dart_Invoke(library, fun, 1, args);
    if (Dart_IsError(result)) {
      fprintf(stderr, "Failed to invoke %s/%s in child isolate: %s\n",
              library_uri, function_name, Dart_GetError(result));
    }
    ENSURE(!Dart_IsError(result));

    Dart_ExitScope();
  }

  char* error = nullptr;
  ENSURE(
      Dart_RunLoopAsync(errors_are_fatal, on_error_port, on_exit_port, &error));

  Dart_EnterIsolate(parent);
}

////////////////////////////////////////////////////////////////////////////////
// Initialize `dart_api_dl.h`
DART_EXPORT intptr_t InitDartApiDL(void* data) {
  return Dart_InitializeApiDL(data);
}

////////////////////////////////////////////////////////////////////////////////
// Functions for async callbacks example.
//
// sample_async_callback.dart

void Fatal(char const* file, int line, char const* error) {
  printf("FATAL %s:%i\n", file, line);
  printf("%s\n", error);
  Dart_DumpNativeStackTrace(nullptr);
  Dart_PrepareToAbort();
  abort();
}

#define FATAL(error) Fatal(__FILE__, __LINE__, error)

DART_EXPORT void SleepOnAnyOS(intptr_t seconds) {
#if defined(DART_HOST_OS_WINDOWS)
  Sleep(1000 * seconds);
#else
  sleep(seconds);
#endif
}

intptr_t (*my_callback_blocking_fp_)(intptr_t);
Dart_Port my_callback_blocking_send_port_;

void (*my_callback_non_blocking_fp_)(intptr_t);
Dart_Port my_callback_non_blocking_send_port_;

typedef std::function<void()> Work;

// Notify Dart through a port that the C lib has pending async callbacks.
//
// Expects heap allocated `work` so delete can be called on it.
//
// The `send_port` should be from the isolate which registered the callback.
void NotifyDart(Dart_Port send_port, const Work* work) {
  const intptr_t work_addr = reinterpret_cast<intptr_t>(work);
  printf("C   :  Posting message (port: %" Px64 ", work: %" Px ").\n",
         send_port, work_addr);

  Dart_CObject dart_object;
  dart_object.type = Dart_CObject_kInt64;
  dart_object.value.as_int64 = work_addr;

  const bool result = Dart_PostCObject_DL(send_port, &dart_object);
  if (!result) {
    FATAL("C   :  Posting message to port failed.");
  }
}

// Do a callback to Dart in a blocking way, being interested in the result.
//
// Dart returns `a + 3`.
intptr_t MyCallbackBlocking(intptr_t a) {
  std::mutex mutex;
  std::unique_lock<std::mutex> lock(mutex);
  intptr_t result;
  auto callback = my_callback_blocking_fp_;  // Define storage duration.
  std::condition_variable cv;
  bool notified = false;
  const Work work = [a, &result, callback, &mutex, &cv, &notified]() {
    result = callback(a);
    printf("C Da:     Notify result ready.\n");
    std::unique_lock<std::mutex> lock(mutex);
    notified = true;
    cv.notify_one();
  };
  const Work* work_ptr = new Work(work);  // Copy to heap.
  NotifyDart(my_callback_blocking_send_port_, work_ptr);
  printf("C   :  Waiting for result.\n");
  while (!notified) {
    cv.wait(lock);
  }
  printf("C   :  Received result.\n");
  return result;
}

// Do a callback to Dart in a non-blocking way.
//
// Dart sums all numbers posted to it.
void MyCallbackNonBlocking(intptr_t a) {
  auto callback = my_callback_non_blocking_fp_;  // Define storage duration.
  const Work work = [a, callback]() { callback(a); };
  // Copy to heap to make it outlive the function scope.
  const Work* work_ptr = new Work(work);
  NotifyDart(my_callback_non_blocking_send_port_, work_ptr);
}

// Simulated work for Thread #1.
//
// Simulates heavy work with sleeps.
void Work1() {
  printf("C T1: Work1 Start.\n");
  SleepOnAnyOS(1);
  const intptr_t val1 = 3;
  printf("C T1: MyCallbackBlocking(%" Pd ").\n", val1);
  const intptr_t val2 = MyCallbackBlocking(val1);  // val2 = 6.
  printf("C T1: MyCallbackBlocking returned %" Pd ".\n", val2);
  SleepOnAnyOS(1);
  const intptr_t val3 = val2 - 1;  // val3 = 5.
  printf("C T1: MyCallbackNonBlocking(%" Pd ").\n", val3);
  MyCallbackNonBlocking(val3);  // Post 5 to Dart.
  printf("C T1: Work1 Done.\n");
}

// Simulated work for Thread #2.
//
// Simulates lighter work, no sleeps.
void Work2() {
  printf("C T2: Work2 Start.\n");
  const intptr_t val1 = 5;
  printf("C T2: MyCallbackNonBlocking(%" Pd ").\n", val1);
  MyCallbackNonBlocking(val1);  // Post 5 to Dart.
  const intptr_t val2 = 1;
  printf("C T2: MyCallbackBlocking(%" Pd ").\n", val2);
  const intptr_t val3 = MyCallbackBlocking(val2);  // val3 = 4.
  printf("C T2: MyCallbackBlocking returned %" Pd ".\n", val3);
  printf("C T2: MyCallbackNonBlocking(%" Pd ").\n", val3);
  MyCallbackNonBlocking(val3);  // Post 4 to Dart.
  printf("C T2: Work2 Done.\n");
}

// Simulator that simulates concurrent work with multiple threads.
class SimulateWork {
 public:
  static void StartWorkSimulator() {
    running_work_simulator_ = new SimulateWork();
    running_work_simulator_->Start();
  }

  static void StopWorkSimulator() {
    running_work_simulator_->Stop();
    delete running_work_simulator_;
    running_work_simulator_ = nullptr;
  }

 private:
  static SimulateWork* running_work_simulator_;

  void Start() {
    printf("C Da:  Starting SimulateWork.\n");
    printf("C Da:   Starting worker threads.\n");
    thread1 = new std::thread(Work1);
    thread2 = new std::thread(Work2);
    printf("C Da:  Started SimulateWork.\n");
  }

  void Stop() {
    printf("C Da:  Stopping SimulateWork.\n");
    printf("C Da:   Waiting for worker threads to finish.\n");
    thread1->join();
    thread2->join();
    delete thread1;
    delete thread2;
    printf("C Da:  Stopped SimulateWork.\n");
  }

  std::thread* thread1;
  std::thread* thread2;
};
SimulateWork* SimulateWork::running_work_simulator_ = 0;

DART_EXPORT void RegisterMyCallbackBlocking(Dart_Port send_port,
                                            intptr_t (*callback1)(intptr_t)) {
  my_callback_blocking_fp_ = callback1;
  my_callback_blocking_send_port_ = send_port;
}

DART_EXPORT void RegisterMyCallbackNonBlocking(Dart_Port send_port,
                                               void (*callback)(intptr_t)) {
  my_callback_non_blocking_fp_ = callback;
  my_callback_non_blocking_send_port_ = send_port;
}

DART_EXPORT void StartWorkSimulator() {
  SimulateWork::StartWorkSimulator();
}

DART_EXPORT void StopWorkSimulator() {
  SimulateWork::StopWorkSimulator();
}

DART_EXPORT void ExecuteCallback(Work* work_ptr) {
  printf("C Da:    ExecuteCallback(%" Pp ").\n",
         reinterpret_cast<intptr_t>(work_ptr));
  const Work work = *work_ptr;
  work();
  delete work_ptr;
  printf("C Da:    ExecuteCallback done.\n");
}

////////////////////////////////////////////////////////////////////////////////
// Functions for async callbacks example.
//
// sample_native_port_call.dart

Dart_Port send_port_;

DART_EXPORT void* Calloc(size_t count, size_t size) {
  return calloc(count, size);
}

DART_EXPORT void FreeFinalizer(void*, void* value) {
  free(value);
}

class PendingCall {
 public:
  PendingCall(void** buffer, size_t* length)
      : response_buffer_(buffer), response_length_(length) {
    receive_port_ =
        Dart_NewNativePort_DL("cpp-response", &PendingCall::HandleResponse,
                              /*handle_concurrently=*/false);
  }
  ~PendingCall() { Dart_CloseNativePort_DL(receive_port_); }

  Dart_Port port() const { return receive_port_; }

  void PostAndWait(Dart_Port port, Dart_CObject* object) {
    std::unique_lock<std::mutex> lock(mutex);
    const bool success = Dart_PostCObject_DL(port, object);
    if (!success) FATAL("Failed to send message, invalid port or isolate died");

    printf("C   :  Waiting for result.\n");
    while (!notified) {
      cv.wait(lock);
    }
  }

  static void HandleResponse(Dart_Port p, Dart_CObject* message) {
    if (message->type != Dart_CObject_kArray) {
      FATAL("C   :   Wrong Data: message->type != Dart_CObject_kArray.\n");
    }
    Dart_CObject** c_response_args = message->value.as_array.values;
    Dart_CObject* c_pending_call = c_response_args[0];
    Dart_CObject* c_message = c_response_args[1];
    printf("C   :   HandleResponse (call: %" Px ", message: %" Px ").\n",
           reinterpret_cast<intptr_t>(c_pending_call),
           reinterpret_cast<intptr_t>(c_message));

    auto pending_call = reinterpret_cast<PendingCall*>(
        c_pending_call->type == Dart_CObject_kInt64
            ? c_pending_call->value.as_int64
            : c_pending_call->value.as_int32);

    pending_call->ResolveCall(c_message);
  }

 private:
  static bool NonEmptyBuffer(void** value) { return *value != nullptr; }

  void ResolveCall(Dart_CObject* bytes) {
    assert(bytes->type == Dart_CObject_kTypedData);
    if (bytes->type != Dart_CObject_kTypedData) {
      FATAL("C   :   Wrong Data: bytes->type != Dart_CObject_kTypedData.\n");
    }
    const intptr_t response_length = bytes->value.as_typed_data.length;
    const uint8_t* response_buffer = bytes->value.as_typed_data.values;
    printf("C   :    ResolveCall(length: %" Pd ", buffer: %" Px ").\n",
           response_length, reinterpret_cast<intptr_t>(response_buffer));

    void* buffer = malloc(response_length);
    memmove(buffer, response_buffer, response_length);

    *response_buffer_ = buffer;
    *response_length_ = response_length;

    printf("C   :     Notify result ready.\n");
    std::unique_lock<std::mutex> lock(mutex);
    notified = true;
    cv.notify_one();
  }

  std::mutex mutex;
  std::condition_variable cv;
  bool notified = false;

  Dart_Port receive_port_;
  void** response_buffer_;
  size_t* response_length_;
};

// Do a callback to Dart in a blocking way, being interested in the result.
//
// Dart returns `a + 3`.
uint8_t MyCallback1(uint8_t a) {
  const char* methodname = "myCallback1";
  size_t request_length = sizeof(uint8_t) * 1;
  void* request_buffer = malloc(request_length);      // FreeFinalizer.
  reinterpret_cast<uint8_t*>(request_buffer)[0] = a;  // Populate buffer.
  void* response_buffer = nullptr;
  size_t response_length = 0;

  PendingCall pending_call(&response_buffer, &response_length);

  Dart_CObject c_send_port;
  c_send_port.type = Dart_CObject_kSendPort;
  c_send_port.value.as_send_port.id = pending_call.port();
  c_send_port.value.as_send_port.origin_id = ILLEGAL_PORT;

  Dart_CObject c_pending_call;
  c_pending_call.type = Dart_CObject_kInt64;
  c_pending_call.value.as_int64 = reinterpret_cast<int64_t>(&pending_call);

  Dart_CObject c_method_name;
  c_method_name.type = Dart_CObject_kString;
  c_method_name.value.as_string = const_cast<char*>(methodname);

  Dart_CObject c_request_data;
  c_request_data.type = Dart_CObject_kExternalTypedData;
  c_request_data.value.as_external_typed_data.type = Dart_TypedData_kUint8;
  c_request_data.value.as_external_typed_data.length = request_length;
  c_request_data.value.as_external_typed_data.data =
      static_cast<uint8_t*>(request_buffer);
  c_request_data.value.as_external_typed_data.peer = request_buffer;
  c_request_data.value.as_external_typed_data.callback = FreeFinalizer;

  Dart_CObject* c_request_arr[] = {&c_send_port, &c_pending_call,
                                   &c_method_name, &c_request_data};
  Dart_CObject c_request;
  c_request.type = Dart_CObject_kArray;
  c_request.value.as_array.values = c_request_arr;
  c_request.value.as_array.length =
      sizeof(c_request_arr) / sizeof(c_request_arr[0]);

  printf("C   :  Dart_PostCObject_(request: %" Px ", call: %" Px ").\n",
         reinterpret_cast<intptr_t>(&c_request),
         reinterpret_cast<intptr_t>(&c_pending_call));
  pending_call.PostAndWait(send_port_, &c_request);
  printf("C   :  Received result.\n");

  const intptr_t result = reinterpret_cast<uint8_t*>(response_buffer)[0];
  free(response_buffer);

  return result;
}

// Do a callback to Dart in a non-blocking way.
//
// Dart sums all numbers posted to it.
void MyCallback2(uint8_t a) {
  const char* methodname = "myCallback2";
  void* request_buffer = malloc(sizeof(uint8_t) * 1);  // FreeFinalizer.
  reinterpret_cast<uint8_t*>(request_buffer)[0] = a;   // Populate buffer.
  const size_t request_length = sizeof(uint8_t) * 1;

  Dart_CObject c_send_port;
  c_send_port.type = Dart_CObject_kNull;

  Dart_CObject c_pending_call;
  c_pending_call.type = Dart_CObject_kNull;

  Dart_CObject c_method_name;
  c_method_name.type = Dart_CObject_kString;
  c_method_name.value.as_string = const_cast<char*>(methodname);

  Dart_CObject c_request_data;
  c_request_data.type = Dart_CObject_kExternalTypedData;
  c_request_data.value.as_external_typed_data.type = Dart_TypedData_kUint8;
  c_request_data.value.as_external_typed_data.length = request_length;
  c_request_data.value.as_external_typed_data.data =
      static_cast<uint8_t*>(request_buffer);
  c_request_data.value.as_external_typed_data.peer = request_buffer;
  c_request_data.value.as_external_typed_data.callback = FreeFinalizer;

  Dart_CObject* c_request_arr[] = {&c_send_port, &c_pending_call,
                                   &c_method_name, &c_request_data};
  Dart_CObject c_request;
  c_request.type = Dart_CObject_kArray;
  c_request.value.as_array.values = c_request_arr;
  c_request.value.as_array.length =
      sizeof(c_request_arr) / sizeof(c_request_arr[0]);

  printf("C   :  Dart_PostCObject_(request: %" Px ", call: %" Px ").\n",
         reinterpret_cast<intptr_t>(&c_request),
         reinterpret_cast<intptr_t>(&c_pending_call));
  Dart_PostCObject_DL(send_port_, &c_request);
}

// Simulated work for Thread #1.
//
// Simulates heavy work with sleeps.
void Work1_2() {
  printf("C T1: Work1 Start.\n");
  SleepOnAnyOS(1);
  const intptr_t val1 = 3;
  printf("C T1: MyCallback1(%" Pd ").\n", val1);
  const intptr_t val2 = MyCallback1(val1);  // val2 = 6.
  printf("C T1: MyCallback1 returned %" Pd ".\n", val2);
  SleepOnAnyOS(1);
  const intptr_t val3 = val2 - 1;  // val3 = 5.
  printf("C T1: MyCallback2(%" Pd ").\n", val3);
  MyCallback2(val3);  // Post 5 to Dart.
  printf("C T1: Work1 Done.\n");
}

// Simulated work for Thread #2.
//
// Simulates lighter work, no sleeps.
void Work2_2() {
  printf("C T2: Work2 Start.\n");
  const intptr_t val1 = 5;
  printf("C T2: MyCallback2(%" Pd ").\n", val1);
  MyCallback2(val1);  // Post 5 to Dart.
  const intptr_t val2 = 1;
  printf("C T2: MyCallback1(%" Pd ").\n", val2);
  const intptr_t val3 = MyCallback1(val2);  // val3 = 4.
  printf("C T2: MyCallback1 returned %" Pd ".\n", val3);
  printf("C T2: MyCallback2(%" Pd ").\n", val3);
  MyCallback2(val3);  // Post 4 to Dart.
  printf("C T2: Work2 Done.\n");
}

// Simulator that simulates concurrent work with multiple threads.
class SimulateWork2 {
 public:
  static void StartWorkSimulator() {
    running_work_simulator_ = new SimulateWork2();
    running_work_simulator_->Start();
  }

  static void StopWorkSimulator() {
    running_work_simulator_->Stop();
    delete running_work_simulator_;
    running_work_simulator_ = nullptr;
  }

 private:
  static SimulateWork2* running_work_simulator_;

  void Start() {
    printf("C Da:  Starting SimulateWork.\n");
    printf("C Da:   Starting worker threads.\n");
    thread1 = new std::thread(Work1_2);
    thread2 = new std::thread(Work2_2);
    printf("C Da:  Started SimulateWork.\n");
  }

  void Stop() {
    printf("C Da:  Stopping SimulateWork.\n");
    printf("C Da:   Waiting for worker threads to finish.\n");
    thread1->join();
    thread2->join();
    delete thread1;
    delete thread2;
    printf("C Da:  Stopped SimulateWork.\n");
  }

  std::thread* thread1;
  std::thread* thread2;
};
SimulateWork2* SimulateWork2::running_work_simulator_ = 0;

DART_EXPORT void RegisterSendPort(Dart_Port send_port) {
  send_port_ = send_port;
}

DART_EXPORT void StartWorkSimulator2() {
  SimulateWork2::StartWorkSimulator();
}

DART_EXPORT void StopWorkSimulator2() {
  SimulateWork2::StopWorkSimulator();
}

////////////////////////////////////////////////////////////////////////////////
// Helpers used for lightweight isolate tests.
////////////////////////////////////////////////////////////////////////////////

DART_EXPORT void ThreadPoolTest_BarrierSync(
    Dart_Isolate (*dart_current_isolate)(),
    void (*dart_enter_isolate)(Dart_Isolate),
    void (*dart_exit_isolate)(),
    intptr_t num_threads) {
  // Guaranteed to be initialized exactly once (no race between multiple
  // threads).
  static std::mutex mutex;
  static std::condition_variable cvar;
  static intptr_t thread_count = 0;

  const Dart_Isolate isolate = dart_current_isolate();
  dart_exit_isolate();
  {
    std::unique_lock<std::mutex> lock(mutex);
    ++thread_count;
    while (thread_count < num_threads) {
      cvar.wait(lock);
    }
    cvar.notify_all();
  }
  dart_enter_isolate(isolate);
}

////////////////////////////////////////////////////////////////////////////////
// Helpers used for isolate exit tests.
////////////////////////////////////////////////////////////////////////////////

// This method consumes and ignores unwind error raised by `Isolate.exit` called
// by dart `callIsolateExit` method.
DART_EXPORT void IsolateExitTest_LookupAndCallIsolateExit(int i) {
  Dart_Handle root_lib = Dart_RootLibrary();
  fprintf(stderr, "IsolateExitTest_LookupAndCallIsolateExit i:%d\n", i);
  if (i > 0) {
    Dart_Handle method_name =
        Dart_NewStringFromCString("recurseLookupAndCallWorker");
    Dart_Handle dart_args[1];
    dart_args[0] = Dart_NewInteger(i - 1);
    Dart_Handle result = Dart_Invoke(root_lib, method_name, 1, dart_args);
    ENSURE(Dart_IsError(result));
  } else {
    Dart_Handle method_name = Dart_NewStringFromCString("callIsolateExit");
    Dart_Handle result = Dart_Invoke(root_lib, method_name, 0, nullptr);
    if (Dart_IsError(result)) {
      fprintf(stderr,
              "%d failed to invoke %s in child isolate: %s, carrying on..\n", i,
              "callIsolateExit", Dart_GetError(result));
    }
    ENSURE(Dart_IsError(result));
  }
}

////////////////////////////////////////////////////////////////////////////////
// Functions for handle tests.
//
// vmspecific_handle_test.dart (statically linked).
// vmspecific_handle_dynamically_linked_test.dart (dynamically linked).

static void RunFinalizer(void* isolate_callback_data, void* peer) {
  printf("Running finalizer for weak handle.\n");
}

// Tests that passing handles through FFI calls works, and that the FFI call
// sets up the VM state etc. correctly so that the handle API calls work.
DART_EXPORT Dart_Handle PassObjectToC(Dart_Handle h) {
  // Can use "h" until this function returns.

  // A persistent handle which outlives this call. Lifetime managed in C.
  auto persistent_handle = Dart_NewPersistentHandle(h);

  Dart_Handle handle_2 = Dart_HandleFromPersistent(persistent_handle);
  Dart_DeletePersistentHandle(persistent_handle);
  if (Dart_IsError(handle_2)) {
    Dart_PropagateError(handle_2);
  }

  Dart_Handle return_value;
  if (!Dart_IsNull(h) && !Dart_IsInteger(h)) {
    // A weak handle which outlives this call. Lifetime managed in C.
    auto weak_handle = Dart_NewWeakPersistentHandle(
        h, reinterpret_cast<void*>(0x1234), 64, RunFinalizer);
    return_value = Dart_HandleFromWeakPersistent(weak_handle);

    // Deleting a weak handle is not required, it deletes itself on
    // finalization.
    // Deleting a weak handle cancels the finalizer.
    Dart_DeleteWeakPersistentHandle(weak_handle);
  } else {
    return_value = h;
  }

  return return_value;
}

DART_EXPORT void ClosureCallbackThroughHandle(void (*callback)(Dart_Handle),
                                              Dart_Handle closureHandle) {
  printf("ClosureCallbackThroughHandle %p %p\n", callback, closureHandle);
  callback(closureHandle);
}

DART_EXPORT Dart_Handle ReturnHandleInCallback(Dart_Handle (*callback)()) {
  printf("ReturnHandleInCallback %p\n", callback);
  Dart_Handle handle = callback();
  if (Dart_IsError(handle)) {
    printf("callback() returned an error, propagating error\n");
    // Do C/C++ resource cleanup if needed, before propagating error.
    Dart_PropagateError(handle);
  }
  return handle;
}

// Recurses til `i` reaches 0. Throws some Dart_Invoke in there as well.
DART_EXPORT Dart_Handle HandleRecursion(Dart_Handle object,
                                        Dart_Handle (*callback)(int64_t),
                                        int64_t i) {
  printf("HandleRecursion %" Pd64 "\n", i);
  const bool do_invoke = i % 3 == 0;
  const bool do_gc = i % 7 == 3;
  if (do_gc) {
    Dart_ExecuteInternalCommand("gc-now", nullptr);
  }
  Dart_Handle result;
  if (do_invoke) {
    Dart_Handle method_name = Dart_NewStringFromCString("a");
    if (Dart_IsError(method_name)) {
      Dart_PropagateError(method_name);
    }
    Dart_Handle arg = Dart_NewInteger(i - 1);
    if (Dart_IsError(arg)) {
      Dart_PropagateError(arg);
    }
    printf("Dart_Invoke\n");
    result = Dart_Invoke(object, method_name, 1, &arg);
  } else {
    printf("callback\n");
    result = callback(i - 1);
  }
  if (do_gc) {
    Dart_ExecuteInternalCommand("gc-now", nullptr);
  }
  if (Dart_IsError(result)) {
    // Do C/C++ resource cleanup if needed, before propagating error.
    printf("Dart_PropagateError %" Pd64 "\n", i);
    Dart_PropagateError(result);
  }
  printf("return %" Pd64 "\n", i);
  return result;
}

DART_EXPORT int64_t HandleReadFieldValue(Dart_Handle handle) {
  printf("HandleReadFieldValue\n");
  Dart_Handle field_name = Dart_NewStringFromCString("a");
  if (Dart_IsError(field_name)) {
    printf("Dart_PropagateError(field_name)\n");
    Dart_PropagateError(field_name);
  }
  Dart_Handle field_value = Dart_GetField(handle, field_name);
  if (Dart_IsError(field_value)) {
    printf("Dart_PropagateError(field_value)\n");
    Dart_PropagateError(field_value);
  }
  int64_t value;
  Dart_Handle err = Dart_IntegerToInt64(field_value, &value);
  if (Dart_IsError(err)) {
    Dart_PropagateError(err);
  }
  return value;
}

// Does not have a handle in it's own signature, so does not enter and exit
// scope in the trampoline.
DART_EXPORT int64_t PropagateErrorWithoutHandle(Dart_Handle (*callback)()) {
  Dart_EnterScope();
  Dart_Handle result = callback();
  if (Dart_IsError(result)) {
    Dart_PropagateError(result);
  }
  Dart_ExitScope();
  return 0;
}

DART_EXPORT Dart_Handle ThrowOnReturnOfError(Dart_Handle (*callback)()) {
  Dart_Handle result = callback();
  const bool is_error = Dart_IsError(result);
  printf("ThrowOnReturnOfError is_error %s\n", is_error ? "true" : "false");
  return result;
}

DART_EXPORT Dart_Handle TrueHandle() {
  return Dart_True();
}

DART_EXPORT Dart_Handle PassObjectToCUseDynamicLinking(Dart_Handle h) {
  auto persistent_handle = Dart_NewPersistentHandle_DL(h);

  Dart_Handle handle_2 = Dart_HandleFromPersistent_DL(persistent_handle);
  Dart_SetPersistentHandle_DL(persistent_handle, h);
  Dart_DeletePersistentHandle_DL(persistent_handle);

  auto weak_handle = Dart_NewWeakPersistentHandle_DL(
      handle_2, reinterpret_cast<void*>(0x1234), 64, RunFinalizer);
  Dart_Handle return_value = Dart_HandleFromWeakPersistent_DL(weak_handle);

  Dart_DeleteWeakPersistentHandle_DL(weak_handle);

  return return_value;
}

////////////////////////////////////////////////////////////////////////////////
// Example for doing closure callbacks with help of `dart_api.h`.
//
// sample_ffi_functions_callbacks_closures.dart

void (*callback_)(Dart_Handle);
Dart_PersistentHandle closure_to_callback_;

DART_EXPORT void RegisterClosureCallbackFP(void (*callback)(Dart_Handle)) {
  callback_ = callback;
}

DART_EXPORT void RegisterClosureCallback(Dart_Handle h) {
  closure_to_callback_ = Dart_NewPersistentHandle_DL(h);
}

DART_EXPORT void InvokeClosureCallback() {
  Dart_Handle closure_handle =
      Dart_HandleFromPersistent_DL(closure_to_callback_);
  callback_(closure_handle);
}

DART_EXPORT void ReleaseClosureCallback() {
  Dart_DeletePersistentHandle_DL(closure_to_callback_);
}

////////////////////////////////////////////////////////////////////////////////
// NativeFinalizer tests

DART_EXPORT void SetArgumentTo42(void* token) {
  *reinterpret_cast<intptr_t*>(token) = 42;
}

////////////////////////////////////////////////////////////////////////////////
// Functions for testing @Native.

DART_EXPORT Dart_Handle GetRootLibraryUrl() {
  Dart_Handle root_lib = Dart_RootLibrary();
  Dart_Handle lib_url = Dart_LibraryUrl(root_lib);
  ENSURE(!Dart_IsError(lib_url));
  return lib_url;
}

intptr_t ReturnIntPtr(intptr_t x) {
  return x;
}

intptr_t PassAsHandle(Dart_Handle handle) {
  intptr_t result = 0;
  ENSURE(!Dart_IsError(Dart_GetNativeInstanceField(handle, 0, &result)));
  return result;
}

intptr_t PassAsPointer(void* ptr) {
  return reinterpret_cast<intptr_t>(ptr);
}

intptr_t PassAsPointerAndValue(void* ptr, intptr_t value) {
  return value;
}

intptr_t PassAsValueAndPointer(intptr_t value, void* ptr) {
  return value;
}

intptr_t* AllocateResource(intptr_t value) {
  return new intptr_t(value);
}

void DeleteResource(intptr_t* resource) {
  delete resource;
}

intptr_t GetResourceValue(intptr_t* resource) {
  return *resource;
}

void DummyResourceFinalizer(void* isolate_peer, void* peer) {
  *reinterpret_cast<intptr_t*>(peer) = 0;
}

void SetResourceFinalizer(Dart_Handle handle, intptr_t* resource) {
  Dart_NewFinalizableHandle(handle, resource, sizeof(Dart_FinalizableHandle),
                            DummyResourceFinalizer);
}

intptr_t AddPtrAndInt(void* self, intptr_t x) {
  return reinterpret_cast<intptr_t>(self) + x;
}

intptr_t AddHandleFieldAndInt(Dart_Handle self, intptr_t x) {
  intptr_t field = 0;
  ENSURE(!Dart_IsError(Dart_GetNativeInstanceField(self, 0, &field)));
  return field + x;
}

intptr_t AddPtrAndPtr(void* self, void* other) {
  return reinterpret_cast<intptr_t>(self) + reinterpret_cast<intptr_t>(other);
}

intptr_t AddHandleFieldAndPtr(Dart_Handle self, void* other) {
  intptr_t field = 0;
  ENSURE(!Dart_IsError(Dart_GetNativeInstanceField(self, 0, &field)));
  return field + reinterpret_cast<intptr_t>(other);
}

intptr_t AddHandleFieldAndHandleField(Dart_Handle self, Dart_Handle other) {
  intptr_t field1 = 0;
  ENSURE(!Dart_IsError(Dart_GetNativeInstanceField(self, 0, &field1)));
  intptr_t field2 = 0;
  ENSURE(!Dart_IsError(Dart_GetNativeInstanceField(other, 0, &field2)));
  return field1 + field2;
}

intptr_t AddPtrAndHandleField(void* self, Dart_Handle other) {
  intptr_t field = 0;
  ENSURE(!Dart_IsError(Dart_GetNativeInstanceField(other, 0, &field)));
  return reinterpret_cast<intptr_t>(self) + field;
}

intptr_t ReturnIntPtrMethod(Dart_Handle self, intptr_t value) {
  return value;
}

static void* FfiNativeResolver(const char* name, uintptr_t args_n) {
  if (strcmp(name, "Dart_SetNativeInstanceField") == 0 && args_n == 3) {
    return reinterpret_cast<void*>(Dart_SetNativeInstanceField);
  }
  if (strcmp(name, "IsThreadInGenerated") == 0 && args_n == 0) {
    return reinterpret_cast<void*>(IsThreadInGenerated);
  }
  if (strcmp(name, "ReturnIntPtr") == 0 && args_n == 1) {
    return reinterpret_cast<void*>(ReturnIntPtr);
  }
  if (strcmp(name, "PassAsHandle") == 0 && args_n == 1) {
    return reinterpret_cast<void*>(PassAsHandle);
  }
  if (strcmp(name, "PassAsPointer") == 0 && args_n == 1) {
    return reinterpret_cast<void*>(PassAsPointer);
  }
  if (strcmp(name, "PassAsPointerAndValue") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(PassAsPointerAndValue);
  }
  if (strcmp(name, "PassAsValueAndPointer") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(PassAsValueAndPointer);
  }
  if (strcmp(name, "AllocateResource") == 0 && args_n == 1) {
    return reinterpret_cast<void*>(AllocateResource);
  }
  if (strcmp(name, "DeleteResource") == 0 && args_n == 1) {
    return reinterpret_cast<void*>(DeleteResource);
  }
  if (strcmp(name, "GetResourceValue") == 0 && args_n == 1) {
    return reinterpret_cast<void*>(GetResourceValue);
  }
  if (strcmp(name, "SetResourceFinalizer") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(SetResourceFinalizer);
  }
  if (strcmp(name, "AddPtrAndInt") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(AddPtrAndInt);
  }
  if (strcmp(name, "AddHandleFieldAndInt") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(AddHandleFieldAndInt);
  }
  if (strcmp(name, "AddPtrAndPtr") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(AddPtrAndPtr);
  }
  if (strcmp(name, "AddHandleFieldAndPtr") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(AddHandleFieldAndPtr);
  }
  if (strcmp(name, "AddHandleFieldAndHandleField") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(AddHandleFieldAndHandleField);
  }
  if (strcmp(name, "AddPtrAndHandleField") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(AddPtrAndHandleField);
  }
  if (strcmp(name, "ReturnIntPtrMethod") == 0 && args_n == 2) {
    return reinterpret_cast<void*>(ReturnIntPtrMethod);
  }
  // This should be unreachable in tests.
  ENSURE(false);
}

DART_EXPORT void SetFfiNativeResolverForTest(Dart_Handle url) {
  Dart_Handle library = Dart_LookupLibrary(url);
  ENSURE(!Dart_IsError(library));
  Dart_Handle result = Dart_SetFfiNativeResolver(library, &FfiNativeResolver);
  ENSURE(!Dart_IsError(result));
}

DART_EXPORT void WaitUntilNThreadsEnterBarrier(intptr_t num_threads) {
  ThreadPoolTest_BarrierSync(Dart_CurrentIsolate_DL, Dart_EnterIsolate_DL,
                             Dart_ExitIsolate_DL, num_threads);
}

////////////////////////////////////////////////////////////////////////////////
// Helper for the regression test for b/216834909
////////////////////////////////////////////////////////////////////////////////

#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID) ||            \
    defined(DART_HOST_OS_MACOS)
static bool Regress216834909_hang_at_exit = true;

static void Regress216834909_AtExit() {
  if (Regress216834909_hang_at_exit) {
    while (true) {
      sleep(60 * 60);  // Sleep for 1 hour.
    }
  }
}

DART_EXPORT void Regress216834909_SetAtExit(int64_t install) {
  if (install != 0) {
    // Set and arm atexit routine.
    atexit(&Regress216834909_AtExit);
    Regress216834909_hang_at_exit = true;
  } else {
    // Disarm atexit routine.
    Regress216834909_hang_at_exit = false;
  }
}
#endif

DART_EXPORT bool IsNull(Dart_Handle object) {
  return Dart_IsNull(object);
}

namespace {
struct RefCountedResource {
  void* resource;
  intptr_t refcount;
};
}  // namespace

// We only ever have one ref counted resource in our test, use global lock.
std::mutex ref_counted_resource_mutex;

DART_EXPORT RefCountedResource* AllocateRefcountedResource() {
  auto peer =
      static_cast<RefCountedResource*>(malloc(sizeof(RefCountedResource)));
  auto resource = malloc(128);
  memset(resource, 0, 128);
  peer->resource = resource;
  peer->refcount = 0;  // We're not going to count the reference here.
  return peer;
}

DART_EXPORT void IncreaseRefcount(RefCountedResource* peer) {
  ref_counted_resource_mutex.lock();
  peer->refcount++;
  ref_counted_resource_mutex.unlock();
}

// And delete if zero.
DART_EXPORT void DecreaseRefcount(void* peer) {
  auto* resource = static_cast<RefCountedResource*>(peer);
  ref_counted_resource_mutex.lock();
  resource->refcount--;
  if (resource->refcount <= 0) {
    free(resource->resource);
    free(peer);
  }
  ref_counted_resource_mutex.unlock();
}

DART_EXPORT void TestDeprecatedSymbols() {
  Dart_UpdateExternalSize_DL(nullptr, 0);
  Dart_UpdateFinalizableExternalSize_DL(nullptr, Dart_Null(), 0);
}

DART_EXPORT void SemanticsUpdateBuilderUpdateNode(
    void* this_,
    int id,
    int flags,
    int actions,
    int maxValueLength,
    int currentValueLength,
    int textSelectionBase,
    int textSelectionExtent,
    int platformViewId,
    int scrollChildren,
    int scrollIndex,
    double scrollPosition,
    double scrollExtentMax,
    double scrollExtentMin,
    double left,
    double top,
    double right,
    double bottom,
    double elevation,
    double thickness,
    Dart_Handle label,
    Dart_Handle labelAttributes,
    Dart_Handle value,
    Dart_Handle valueAttributes,
    Dart_Handle increasedValue,
    Dart_Handle increasedValueAttributes,
    Dart_Handle decreasedValue,
    Dart_Handle decreasedValueAttributes,
    Dart_Handle hint,
    Dart_Handle hintAttributes,
    Dart_Handle tooltip,
    int textDirection,
    Dart_Handle transform,
    Dart_Handle childrenInTraversalOrder,
    Dart_Handle childrenInHitTestOrder,
    Dart_Handle localContextActions) {
  if (!Dart_IsString(tooltip)) {
    FATAL("expected Dart_IsString(tooltip)");
  }
  const char* cstr;
  auto to_cstring_result = Dart_StringToCString(tooltip, &cstr);
  if (Dart_IsError(to_cstring_result)) {
    FATAL(Dart_GetError(to_cstring_result));
  }
  if (strcmp(cstr, "tooltip") != 0) {
    printf("cstr %s\n", cstr);
    FATAL("cstr not equal to \"tooltip\"");
  }
}

DART_EXPORT void ManyHandles(Dart_Handle o0,
                             Dart_Handle o1,
                             Dart_Handle o2,
                             Dart_Handle o3,
                             Dart_Handle o4,
                             Dart_Handle o5,
                             Dart_Handle o6,
                             Dart_Handle o7,
                             Dart_Handle o8,
                             Dart_Handle o9,
                             Dart_Handle o10,
                             Dart_Handle o11,
                             Dart_Handle o12,
                             Dart_Handle o13,
                             Dart_Handle o14,
                             Dart_Handle o15,
                             Dart_Handle o16,
                             Dart_Handle o17,
                             Dart_Handle o18,
                             Dart_Handle o19) {
#define CHECK_STRING(o)                                                        \
  if (!Dart_IsString(o)) {                                                     \
    FATAL("expected Dart_IsString");                                           \
  }
  CHECK_STRING(o0);
  CHECK_STRING(o1);
  CHECK_STRING(o2);
  CHECK_STRING(o3);
  CHECK_STRING(o4);
  CHECK_STRING(o5);
  CHECK_STRING(o6);
  CHECK_STRING(o7);
  CHECK_STRING(o8);
  CHECK_STRING(o9);
  CHECK_STRING(o10);
  CHECK_STRING(o11);
  CHECK_STRING(o12);
  CHECK_STRING(o13);
  CHECK_STRING(o14);
  CHECK_STRING(o15);
  CHECK_STRING(o16);
  CHECK_STRING(o17);
  CHECK_STRING(o18);
  CHECK_STRING(o19);
}
#undef CHECK_STRING

}  // namespace dart