// Copyright (c) 2012, 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.

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

#include <memory>

#include "bin/builtin.h"
#include "bin/console.h"
#include "bin/crashpad.h"
#include "bin/dartdev_isolate.h"
#include "bin/dartutils.h"
#include "bin/dfe.h"
#include "bin/error_exit.h"
#include "bin/eventhandler.h"
#include "bin/file.h"
#include "bin/gzip.h"
#include "bin/isolate_data.h"
#include "bin/loader.h"
#include "bin/main_options.h"
#include "bin/platform.h"
#include "bin/process.h"
#include "bin/snapshot_utils.h"
#include "bin/thread.h"
#include "bin/utils.h"
#include "bin/vmservice_impl.h"
#include "include/bin/dart_io_api.h"
#include "include/dart_api.h"
#include "include/dart_embedder_api.h"
#include "include/dart_tools_api.h"
#include "platform/globals.h"
#include "platform/growable_array.h"
#include "platform/hashmap.h"
#include "platform/syslog.h"
#include "platform/text_buffer.h"
#include "platform/utils.h"

extern "C" {
extern const uint8_t kDartVmSnapshotData[];
extern const uint8_t kDartVmSnapshotInstructions[];
extern const uint8_t kDartCoreIsolateSnapshotData[];
extern const uint8_t kDartCoreIsolateSnapshotInstructions[];
}

namespace dart {
namespace bin {

// Snapshot pieces we link in a snapshot.
const uint8_t* vm_snapshot_data = kDartVmSnapshotData;
const uint8_t* vm_snapshot_instructions = kDartVmSnapshotInstructions;
const uint8_t* core_isolate_snapshot_data = kDartCoreIsolateSnapshotData;
const uint8_t* core_isolate_snapshot_instructions =
    kDartCoreIsolateSnapshotInstructions;

/**
 * Global state used to control and store generation of application snapshots.
 * An application snapshot can be generated and run using the following
 * command
 *   dart --snapshot-kind=app-jit --snapshot=<app_snapshot_filename>
 *       <script_uri> [<script_options>]
 * To Run the application snapshot generated above, use :
 *   dart <app_snapshot_filename> [<script_options>]
 */
static bool vm_run_app_snapshot = false;
static char* app_script_uri = NULL;
static const uint8_t* app_isolate_snapshot_data = NULL;
static const uint8_t* app_isolate_snapshot_instructions = NULL;
static bool kernel_isolate_is_running = false;

static Dart_Isolate main_isolate = NULL;

#define SAVE_ERROR_AND_EXIT(result)                                            \
  *error = Utils::StrDup(Dart_GetError(result));                               \
  if (Dart_IsCompilationError(result)) {                                       \
    *exit_code = kCompilationErrorExitCode;                                    \
  } else if (Dart_IsApiError(result)) {                                        \
    *exit_code = kApiErrorExitCode;                                            \
  } else {                                                                     \
    *exit_code = kErrorExitCode;                                               \
  }                                                                            \
  Dart_ExitScope();                                                            \
  Dart_ShutdownIsolate();                                                      \
  return NULL;

#define CHECK_RESULT(result)                                                   \
  if (Dart_IsError(result)) {                                                  \
    SAVE_ERROR_AND_EXIT(result);                                               \
  }

#define CHECK_RESULT_CLEANUP(result, cleanup)                                  \
  if (Dart_IsError(result)) {                                                  \
    delete (cleanup);                                                          \
    SAVE_ERROR_AND_EXIT(result);                                               \
  }

static void WriteDepsFile(Dart_Isolate isolate) {
  if (Options::depfile() == NULL) {
    return;
  }
  File* file = File::Open(NULL, Options::depfile(), File::kWriteTruncate);
  if (file == NULL) {
    ErrorExit(kErrorExitCode, "Error: Unable to open snapshot depfile: %s\n\n",
              Options::depfile());
  }
  bool success = true;
  if (Options::depfile_output_filename() != NULL) {
    success &= file->Print("%s: ", Options::depfile_output_filename());
  } else {
    success &= file->Print("%s: ", Options::snapshot_filename());
  }
  if (kernel_isolate_is_running) {
    Dart_KernelCompilationResult result = Dart_KernelListDependencies();
    if (result.status != Dart_KernelCompilationStatus_Ok) {
      ErrorExit(
          kErrorExitCode,
          "Error: Failed to fetch dependencies from kernel service: %s\n\n",
          result.error);
    }
    success &= file->WriteFully(result.kernel, result.kernel_size);
    free(result.kernel);
  }
  success &= file->Print("\n");
  if (!success) {
    ErrorExit(kErrorExitCode, "Error: Unable to write snapshot depfile: %s\n\n",
              Options::depfile());
  }
  file->Release();
}

static void OnExitHook(int64_t exit_code) {
  if (Dart_CurrentIsolate() != main_isolate) {
    Syslog::PrintErr(
        "A snapshot was requested, but a secondary isolate "
        "performed a hard exit (%" Pd64 ").\n",
        exit_code);
    Platform::Exit(kErrorExitCode);
  }
  if (exit_code == 0) {
    if (Options::gen_snapshot_kind() == kAppJIT) {
      Snapshot::GenerateAppJIT(Options::snapshot_filename());
    }
    WriteDepsFile(main_isolate);
  }
}

static Dart_Handle SetupCoreLibraries(Dart_Isolate isolate,
                                      IsolateData* isolate_data,
                                      bool is_isolate_group_start,
                                      const char** resolved_packages_config) {
  auto isolate_group_data = isolate_data->isolate_group_data();
  const auto packages_file = isolate_data->packages_file();
  const auto script_uri = isolate_group_data->script_url;

  Dart_Handle result;

  // Prepare builtin and other core libraries for use to resolve URIs.
  // Set up various closures, e.g: printing, timers etc.
  // Set up package configuration for URI resolution.
  result = DartUtils::PrepareForScriptLoading(false, Options::trace_loading());
  if (Dart_IsError(result)) return result;

  // Setup packages config if specified.
  result = DartUtils::SetupPackageConfig(packages_file);
  if (Dart_IsError(result)) return result;
  if (!Dart_IsNull(result) && resolved_packages_config != nullptr) {
    result = Dart_StringToCString(result, resolved_packages_config);
    if (Dart_IsError(result)) return result;
    ASSERT(*resolved_packages_config != nullptr);
#if !defined(DART_PRECOMPILED_RUNTIME)
    if (is_isolate_group_start) {
      isolate_group_data->set_resolved_packages_config(
          *resolved_packages_config);
    } else {
      ASSERT(strcmp(isolate_group_data->resolved_packages_config(),
                    *resolved_packages_config) == 0);
    }
#endif
  }

  result = Dart_SetEnvironmentCallback(DartUtils::EnvironmentCallback);
  if (Dart_IsError(result)) return result;

  // Setup the native resolver as the snapshot does not carry it.
  Builtin::SetNativeResolver(Builtin::kBuiltinLibrary);
  Builtin::SetNativeResolver(Builtin::kIOLibrary);
  Builtin::SetNativeResolver(Builtin::kCLILibrary);
  VmService::SetNativeResolver();

  const char* namespc =
      Dart_IsKernelIsolate(isolate) ? NULL : Options::namespc();
  result =
      DartUtils::SetupIOLibrary(namespc, script_uri, Options::exit_disabled());
  if (Dart_IsError(result)) return result;

  return Dart_Null();
}

static bool OnIsolateInitialize(void** child_callback_data, char** error) {
  Dart_Isolate isolate = Dart_CurrentIsolate();
  ASSERT(isolate != nullptr);

  auto isolate_group_data =
      reinterpret_cast<IsolateGroupData*>(Dart_CurrentIsolateGroupData());

  auto isolate_data = new IsolateData(isolate_group_data);
  *child_callback_data = isolate_data;

  Dart_EnterScope();
  const auto script_uri = isolate_group_data->script_url;
  const bool isolate_run_app_snapshot =
      isolate_group_data->RunFromAppSnapshot();
  Dart_Handle result = SetupCoreLibraries(isolate, isolate_data,
                                          /*group_start=*/false,
                                          /*resolved_packages_config=*/nullptr);
  if (Dart_IsError(result)) goto failed;

  if (isolate_run_app_snapshot) {
    result = Loader::InitForSnapshot(script_uri, isolate_data);
    if (Dart_IsError(result)) goto failed;
  } else {
    result = DartUtils::ResolveScript(Dart_NewStringFromCString(script_uri));
    if (Dart_IsError(result)) return result != nullptr;

    if (isolate_group_data->kernel_buffer().get() != nullptr) {
      // Various core-library parts will send requests to the Loader to resolve
      // relative URIs and perform other related tasks. We need Loader to be
      // initialized for this to work because loading from Kernel binary
      // bypasses normal source code loading paths that initialize it.
      const char* resolved_script_uri = NULL;
      result = Dart_StringToCString(result, &resolved_script_uri);
      if (Dart_IsError(result)) goto failed;
      result = Loader::InitForSnapshot(resolved_script_uri, isolate_data);
      if (Dart_IsError(result)) goto failed;
    }
  }

  Dart_ExitScope();
  return true;

failed:
  *error = Utils::StrDup(Dart_GetError(result));
  Dart_ExitScope();
  return false;
}

static Dart_Isolate IsolateSetupHelper(Dart_Isolate isolate,
                                       bool is_main_isolate,
                                       const char* script_uri,
                                       const char* packages_config,
                                       bool isolate_run_app_snapshot,
                                       Dart_IsolateFlags* flags,
                                       char** error,
                                       int* exit_code) {
  Dart_EnterScope();

  // Set up the library tag handler for the isolate group shared by all
  // isolates in the group.
  Dart_Handle result = Dart_SetLibraryTagHandler(Loader::LibraryTagHandler);
  CHECK_RESULT(result);
  result = Dart_SetDeferredLoadHandler(Loader::DeferredLoadHandler);
  CHECK_RESULT(result);

  auto isolate_data = reinterpret_cast<IsolateData*>(Dart_IsolateData(isolate));

  const char* resolved_packages_config = nullptr;
  result = SetupCoreLibraries(isolate, isolate_data,
                              /*is_isolate_group_start=*/true,
                              &resolved_packages_config);
  CHECK_RESULT(result);

#if !defined(DART_PRECOMPILED_RUNTIME)
  auto isolate_group_data = isolate_data->isolate_group_data();
  const uint8_t* kernel_buffer = isolate_group_data->kernel_buffer().get();
  intptr_t kernel_buffer_size = isolate_group_data->kernel_buffer_size();
  if (!isolate_run_app_snapshot && kernel_buffer == NULL &&
      !Dart_IsKernelIsolate(isolate)) {
    if (!dfe.CanUseDartFrontend()) {
      const char* format = "Dart frontend unavailable to compile script %s.";
      intptr_t len = snprintf(NULL, 0, format, script_uri) + 1;
      *error = reinterpret_cast<char*>(malloc(len));
      ASSERT(error != NULL);
      snprintf(*error, len, format, script_uri);
      *exit_code = kErrorExitCode;
      Dart_ExitScope();
      Dart_ShutdownIsolate();
      return NULL;
    }
    uint8_t* application_kernel_buffer = NULL;
    intptr_t application_kernel_buffer_size = 0;
    // Only pass snapshot = true when generating an AppJIT snapshot to avoid
    // duplicate null-safety info messages from the frontend when generating
    // a kernel snapshot (this flag is instead set in
    // Snapshot::GenerateKernel()).
    const bool snapshot = Options::gen_snapshot_kind() == kAppJIT;
    dfe.CompileAndReadScript(script_uri, &application_kernel_buffer,
                             &application_kernel_buffer_size, error, exit_code,
                             resolved_packages_config, snapshot);
    if (application_kernel_buffer == NULL) {
      Dart_ExitScope();
      Dart_ShutdownIsolate();
      return NULL;
    }
    isolate_group_data->SetKernelBufferNewlyOwned(
        application_kernel_buffer, application_kernel_buffer_size);
    kernel_buffer = application_kernel_buffer;
    kernel_buffer_size = application_kernel_buffer_size;
  }
  if (kernel_buffer != NULL) {
    Dart_Handle uri = Dart_NewStringFromCString(script_uri);
    CHECK_RESULT(uri);
    Dart_Handle resolved_script_uri = DartUtils::ResolveScript(uri);
    CHECK_RESULT(resolved_script_uri);
    result = Dart_LoadScriptFromKernel(kernel_buffer, kernel_buffer_size);
    CHECK_RESULT(result);
  }
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

  if (isolate_run_app_snapshot) {
    Dart_Handle result = Loader::InitForSnapshot(script_uri, isolate_data);
    CHECK_RESULT(result);
#if !defined(DART_PRECOMPILED_RUNTIME)
    if (is_main_isolate) {
      // Find the canonical uri of the app snapshot. We'll use this to decide if
      // other isolates should use the app snapshot or the core snapshot.
      const char* resolved_script_uri = NULL;
      result = Dart_StringToCString(
          DartUtils::ResolveScript(Dart_NewStringFromCString(script_uri)),
          &resolved_script_uri);
      CHECK_RESULT(result);
      ASSERT(app_script_uri == NULL);
      app_script_uri = Utils::StrDup(resolved_script_uri);
    }
#endif  // !defined(DART_PRECOMPILED_RUNTIME)
  } else {
#if !defined(DART_PRECOMPILED_RUNTIME)
    // Load the specified application script into the newly created isolate.
    Dart_Handle uri =
        DartUtils::ResolveScript(Dart_NewStringFromCString(script_uri));
    CHECK_RESULT(uri);
    if (kernel_buffer != NULL) {
      // relative URIs and perform other related tasks. We need Loader to be
      // initialized for this to work because loading from Kernel binary
      // bypasses normal source code loading paths that initialize it.
      const char* resolved_script_uri = NULL;
      result = Dart_StringToCString(uri, &resolved_script_uri);
      CHECK_RESULT(result);
      result = Loader::InitForSnapshot(resolved_script_uri, isolate_data);
      CHECK_RESULT(result);
    }
    Dart_TimelineEvent("LoadScript", Dart_TimelineGetMicros(),
                       Dart_GetMainPortId(), Dart_Timeline_Event_Async_End, 0,
                       NULL, NULL);
#else
    UNREACHABLE();
#endif  // !defined(DART_PRECOMPILED_RUNTIME)
  }

  if (Options::gen_snapshot_kind() == kAppJIT && !isolate_run_app_snapshot) {
    // If we sort, we must do it for all isolates, not just the main isolate,
    // otherwise isolates related by spawnFunction will disagree on CIDs and
    // cannot correctly send each other messages. If we run from an app
    // snapshot, things are already sorted, and other isolate created by
    // spawnFunction will also load from the same snapshot. Sorting such isolate
    // is counter-productive because it invalidates their code.
    // After we switch to always using isolate groups, this be changed to
    // `generating-app-jit && is_main_isolate`.
    result = Dart_SortClasses();
    CHECK_RESULT(result);
  }

  // Disable pausing the DartDev isolate on start and exit.
  const char* isolate_name = nullptr;
  result = Dart_StringToCString(Dart_DebugName(), &isolate_name);
  CHECK_RESULT(result);
#if !defined(DART_PRECOMPILED_RUNTIME)
  if (strstr(isolate_name, DART_DEV_ISOLATE_NAME) != nullptr) {
    Dart_SetShouldPauseOnStart(false);
    Dart_SetShouldPauseOnExit(false);
  }
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

  // Make the isolate runnable so that it is ready to handle messages.
  Dart_ExitScope();
  Dart_ExitIsolate();
  *error = Dart_IsolateMakeRunnable(isolate);
  if (*error != NULL) {
    Dart_EnterIsolate(isolate);
    Dart_ShutdownIsolate();
    return NULL;
  }

  return isolate;
}

#if !defined(EXCLUDE_CFE_AND_KERNEL_PLATFORM)
// Returns newly created Kernel Isolate on success, NULL on failure.
// For now we only support the kernel isolate coming up from an
// application snapshot or from a .dill file.
static Dart_Isolate CreateAndSetupKernelIsolate(const char* script_uri,
                                                const char* packages_config,
                                                Dart_IsolateFlags* flags,
                                                char** error,
                                                int* exit_code) {
  // Do not start a kernel isolate if we are doing a training run
  // to create an app JIT snapshot and a kernel file is specified
  // as the application to run.
  if (Options::gen_snapshot_kind() == kAppJIT) {
    const uint8_t* kernel_buffer = NULL;
    intptr_t kernel_buffer_size = 0;
    dfe.application_kernel_buffer(&kernel_buffer, &kernel_buffer_size);
    if (kernel_buffer_size != 0) {
      return NULL;
    }
  }
  // Create and Start the kernel isolate.
  const char* kernel_snapshot_uri = dfe.frontend_filename();
  const char* uri =
      kernel_snapshot_uri != NULL ? kernel_snapshot_uri : script_uri;

  if (packages_config == NULL) {
    packages_config = Options::packages_file();
  }

  Dart_Isolate isolate = NULL;
  IsolateGroupData* isolate_group_data = nullptr;
  IsolateData* isolate_data = nullptr;
  bool isolate_run_app_snapshot = false;
  AppSnapshot* app_snapshot = NULL;
  // Kernel isolate uses an app snapshot or uses the dill file.
  if ((kernel_snapshot_uri != NULL) &&
      (app_snapshot = Snapshot::TryReadAppSnapshot(
           kernel_snapshot_uri, /*force_load_elf_from_memory=*/false,
           /*decode_uri=*/false)) != nullptr) {
    const uint8_t* isolate_snapshot_data = NULL;
    const uint8_t* isolate_snapshot_instructions = NULL;
    const uint8_t* ignore_vm_snapshot_data;
    const uint8_t* ignore_vm_snapshot_instructions;
    isolate_run_app_snapshot = true;
    app_snapshot->SetBuffers(
        &ignore_vm_snapshot_data, &ignore_vm_snapshot_instructions,
        &isolate_snapshot_data, &isolate_snapshot_instructions);
    isolate_group_data = new IsolateGroupData(
        uri, packages_config, app_snapshot, isolate_run_app_snapshot);
    isolate_data = new IsolateData(isolate_group_data);
    isolate = Dart_CreateIsolateGroup(
        DART_KERNEL_ISOLATE_NAME, DART_KERNEL_ISOLATE_NAME,
        isolate_snapshot_data, isolate_snapshot_instructions, flags,
        isolate_group_data, isolate_data, error);
  }
  if (isolate == NULL) {
    // Clear error from app snapshot and re-trying from kernel file.
    free(*error);
    *error = NULL;
    delete isolate_data;
    delete isolate_group_data;

    const uint8_t* kernel_service_buffer = NULL;
    intptr_t kernel_service_buffer_size = 0;
    dfe.LoadKernelService(&kernel_service_buffer, &kernel_service_buffer_size);
    ASSERT(kernel_service_buffer != NULL);
    isolate_group_data = new IsolateGroupData(uri, packages_config, nullptr,
                                              isolate_run_app_snapshot);
    isolate_group_data->SetKernelBufferUnowned(
        const_cast<uint8_t*>(kernel_service_buffer),
        kernel_service_buffer_size);
    isolate_data = new IsolateData(isolate_group_data);
    isolate = Dart_CreateIsolateGroupFromKernel(
        DART_KERNEL_ISOLATE_NAME, DART_KERNEL_ISOLATE_NAME,
        kernel_service_buffer, kernel_service_buffer_size, flags,
        isolate_group_data, isolate_data, error);
  }

  if (isolate == NULL) {
    Syslog::PrintErr("%s\n", *error);
    delete isolate_data;
    delete isolate_group_data;
    return NULL;
  }
  kernel_isolate_is_running = true;

  return IsolateSetupHelper(isolate, false, uri, packages_config,
                            isolate_run_app_snapshot, flags, error, exit_code);
}
#endif  // !defined(EXCLUDE_CFE_AND_KERNEL_PLATFORM)

// Returns newly created Service Isolate on success, NULL on failure.
// For now we only support the service isolate coming up from sources
// which are compiled by the VM parser.
static Dart_Isolate CreateAndSetupServiceIsolate(const char* script_uri,
                                                 const char* packages_config,
                                                 Dart_IsolateFlags* flags,
                                                 char** error,
                                                 int* exit_code) {
#if !defined(PRODUCT)
  ASSERT(script_uri != nullptr);
  Dart_Isolate isolate = nullptr;
  auto isolate_group_data =
      new IsolateGroupData(script_uri, packages_config, nullptr, false);
  ASSERT(flags != nullptr);

#if defined(DART_PRECOMPILED_RUNTIME)
  // AOT: All isolates start from the app snapshot.
  const uint8_t* isolate_snapshot_data = app_isolate_snapshot_data;
  const uint8_t* isolate_snapshot_instructions =
      app_isolate_snapshot_instructions;
  flags->null_safety =
      Dart_DetectNullSafety(nullptr, nullptr, nullptr, isolate_snapshot_data,
                            isolate_snapshot_instructions, nullptr, -1);
  isolate = Dart_CreateIsolateGroup(
      script_uri, DART_VM_SERVICE_ISOLATE_NAME, isolate_snapshot_data,
      isolate_snapshot_instructions, flags, isolate_group_data,
      /*isolate_data=*/nullptr, error);
#else
  // JIT: Service isolate uses the core libraries snapshot.

  // Set flag to load and retain the vmservice library.
  flags->load_vmservice_library = true;
  const uint8_t* isolate_snapshot_data = core_isolate_snapshot_data;
  const uint8_t* isolate_snapshot_instructions =
      core_isolate_snapshot_instructions;
  isolate = Dart_CreateIsolateGroup(
      script_uri, DART_VM_SERVICE_ISOLATE_NAME, isolate_snapshot_data,
      isolate_snapshot_instructions, flags, isolate_group_data,
      /*isolate_data=*/nullptr, error);
#endif  // !defined(DART_PRECOMPILED_RUNTIME)
  if (isolate == NULL) {
    delete isolate_group_data;
    return NULL;
  }

  Dart_EnterScope();

  Dart_Handle result = Dart_SetLibraryTagHandler(Loader::LibraryTagHandler);
  CHECK_RESULT(result);
  result = Dart_SetDeferredLoadHandler(Loader::DeferredLoadHandler);
  CHECK_RESULT(result);

  int vm_service_server_port = INVALID_VM_SERVICE_SERVER_PORT;
  if (Options::disable_dart_dev() || Options::disable_dds()) {
    vm_service_server_port = Options::vm_service_server_port();
  } else if (Options::vm_service_server_port() !=
             INVALID_VM_SERVICE_SERVER_PORT) {
    vm_service_server_port = 0;
  }

  // We do not want to wait for DDS to advertise availability of VM service in
  // the following scenarios:
  // - The DartDev CLI is disabled (CLI isolate starts DDS) and VM service is
  //   enabled.
  // - DDS is disabled.
  // TODO(bkonyi): do we want to tie DevTools / DDS to the CLI in the long run?
  bool wait_for_dds_to_advertise_service =
      !(Options::disable_dart_dev() || Options::disable_dds());
  // Load embedder specific bits and return.
  if (!VmService::Setup(
          !wait_for_dds_to_advertise_service ? Options::vm_service_server_ip()
                                             : DEFAULT_VM_SERVICE_SERVER_IP,
          vm_service_server_port, Options::vm_service_dev_mode(),
          Options::vm_service_auth_disabled(),
          Options::vm_write_service_info_filename(), Options::trace_loading(),
          Options::deterministic(), Options::enable_service_port_fallback(),
          wait_for_dds_to_advertise_service)) {
    *error = Utils::StrDup(VmService::GetErrorMessage());
    return NULL;
  }
  if (Options::compile_all()) {
    result = Dart_CompileAll();
    CHECK_RESULT(result);
  }
  result = Dart_SetEnvironmentCallback(DartUtils::EnvironmentCallback);
  CHECK_RESULT(result);
  Dart_ExitScope();
  Dart_ExitIsolate();
  return isolate;
#else   // !defined(PRODUCT)
  return NULL;
#endif  // !defined(PRODUCT)
}

#if !defined(DART_PRECOMPILED_RUNTIME)

static Dart_Isolate CreateAndSetupDartDevIsolate(const char* script_uri,
                                                 const char* packages_config,
                                                 Dart_IsolateFlags* flags,
                                                 char** error,
                                                 int* exit_code) {
  int64_t start = Dart_TimelineGetMicros();

  auto dartdev_path = DartDevIsolate::TryResolveDartDevSnapshotPath();

  Dart_Isolate isolate = nullptr;
  const uint8_t* isolate_snapshot_data = core_isolate_snapshot_data;
  const uint8_t* isolate_snapshot_instructions =
      core_isolate_snapshot_instructions;
  IsolateGroupData* isolate_group_data = nullptr;
  IsolateData* isolate_data = nullptr;

  if (error != nullptr) {
    *error = nullptr;
  }
  AppSnapshot* app_snapshot = nullptr;
  bool isolate_run_app_snapshot = true;
  if (dartdev_path.get() != nullptr &&
      (app_snapshot = Snapshot::TryReadAppSnapshot(
           dartdev_path.get(), /*force_load_elf_from_memory=*/false,
           /*decode_uri=*/false)) != nullptr) {
    const uint8_t* isolate_snapshot_data = NULL;
    const uint8_t* isolate_snapshot_instructions = NULL;
    const uint8_t* ignore_vm_snapshot_data;
    const uint8_t* ignore_vm_snapshot_instructions;
    app_snapshot->SetBuffers(
        &ignore_vm_snapshot_data, &ignore_vm_snapshot_instructions,
        &isolate_snapshot_data, &isolate_snapshot_instructions);
    isolate_group_data =
        new IsolateGroupData(DART_DEV_ISOLATE_NAME, packages_config,
                             app_snapshot, isolate_run_app_snapshot);
    isolate_data = new IsolateData(isolate_group_data);
    isolate = Dart_CreateIsolateGroup(
        DART_DEV_ISOLATE_NAME, DART_DEV_ISOLATE_NAME, isolate_snapshot_data,
        isolate_snapshot_instructions, flags, isolate_group_data, isolate_data,
        error);
  }

  if (isolate == nullptr) {
    isolate_run_app_snapshot = false;
    dartdev_path = DartDevIsolate::TryResolveDartDevKernelPath();
    // Clear error from app snapshot and retry from kernel.
    if (error != nullptr && *error != nullptr) {
      free(*error);
      *error = nullptr;
    }

    if (app_snapshot != nullptr) {
      delete app_snapshot;
    }

    if (dartdev_path.get() != nullptr) {
      isolate_group_data =
          new IsolateGroupData(DART_DEV_ISOLATE_NAME, packages_config, nullptr,
                               isolate_run_app_snapshot);
      uint8_t* application_kernel_buffer = NULL;
      intptr_t application_kernel_buffer_size = 0;
      dfe.ReadScript(dartdev_path.get(), &application_kernel_buffer,
                     &application_kernel_buffer_size, /*decode_uri=*/false);
      isolate_group_data->SetKernelBufferNewlyOwned(
          application_kernel_buffer, application_kernel_buffer_size);

      isolate_data = new IsolateData(isolate_group_data);
      isolate = Dart_CreateIsolateGroup(
          DART_DEV_ISOLATE_NAME, DART_DEV_ISOLATE_NAME, isolate_snapshot_data,
          isolate_snapshot_instructions, flags, isolate_group_data,
          isolate_data, error);
    }
  }

  Dart_Isolate created_isolate = nullptr;
  if (isolate == nullptr) {
    Syslog::PrintErr("Failed to start the Dart CLI isolate\n");
    delete isolate_data;
    delete isolate_group_data;
    return nullptr;
  } else {
    created_isolate = IsolateSetupHelper(
        isolate, false, DART_DEV_ISOLATE_NAME, packages_config,
        isolate_run_app_snapshot, flags, error, exit_code);
  }
  int64_t end = Dart_TimelineGetMicros();
  Dart_TimelineEvent("CreateAndSetupDartDevIsolate", start, end,
                     Dart_Timeline_Event_Duration, 0, NULL, NULL);
  return created_isolate;
}

#endif  // !defined(DART_PRECOMPILED_RUNTIME)

// Returns newly created Isolate on success, NULL on failure.
static Dart_Isolate CreateIsolateGroupAndSetupHelper(
    bool is_main_isolate,
    const char* script_uri,
    const char* name,
    const char* packages_config,
    Dart_IsolateFlags* flags,
    void* callback_data,
    char** error,
    int* exit_code) {
  int64_t start = Dart_TimelineGetMicros();
  ASSERT(script_uri != NULL);
  uint8_t* kernel_buffer = NULL;
  std::shared_ptr<uint8_t> parent_kernel_buffer;
  intptr_t kernel_buffer_size = 0;
  AppSnapshot* app_snapshot = NULL;

#if defined(DART_PRECOMPILED_RUNTIME)
  // AOT: All isolates start from the app snapshot.
  bool isolate_run_app_snapshot = true;
  const uint8_t* isolate_snapshot_data = app_isolate_snapshot_data;
  const uint8_t* isolate_snapshot_instructions =
      app_isolate_snapshot_instructions;
  flags->null_safety =
      Dart_DetectNullSafety(nullptr, nullptr, nullptr, isolate_snapshot_data,
                            isolate_snapshot_instructions, nullptr, -1);
#else
  // JIT: Main isolate starts from the app snapshot, if any. Other isolates
  // use the core libraries snapshot.
  bool isolate_run_app_snapshot = false;
  const uint8_t* isolate_snapshot_data = core_isolate_snapshot_data;
  const uint8_t* isolate_snapshot_instructions =
      core_isolate_snapshot_instructions;
  if ((app_isolate_snapshot_data != NULL) &&
      (is_main_isolate || ((app_script_uri != NULL) &&
                           (strcmp(script_uri, app_script_uri) == 0)))) {
    isolate_run_app_snapshot = true;
    isolate_snapshot_data = app_isolate_snapshot_data;
    isolate_snapshot_instructions = app_isolate_snapshot_instructions;
  } else if (!is_main_isolate) {
    app_snapshot = Snapshot::TryReadAppSnapshot(script_uri);
    if (app_snapshot != NULL) {
      isolate_run_app_snapshot = true;
      const uint8_t* ignore_vm_snapshot_data;
      const uint8_t* ignore_vm_snapshot_instructions;
      app_snapshot->SetBuffers(
          &ignore_vm_snapshot_data, &ignore_vm_snapshot_instructions,
          &isolate_snapshot_data, &isolate_snapshot_instructions);
    }
  }

  if (flags->copy_parent_code && callback_data != nullptr) {
    auto parent_isolate_group_data =
        reinterpret_cast<IsolateData*>(callback_data)->isolate_group_data();
    parent_kernel_buffer = parent_isolate_group_data->kernel_buffer();
    kernel_buffer = parent_kernel_buffer.get();
    kernel_buffer_size = parent_isolate_group_data->kernel_buffer_size();
  }

  if (kernel_buffer == NULL && !isolate_run_app_snapshot) {
    dfe.ReadScript(script_uri, &kernel_buffer, &kernel_buffer_size);
  }
  PathSanitizer script_uri_sanitizer(script_uri);
  PathSanitizer packages_config_sanitizer(packages_config);
  flags->null_safety = Dart_DetectNullSafety(
      script_uri_sanitizer.sanitized_uri(),
      packages_config_sanitizer.sanitized_uri(),
      DartUtils::original_working_directory, isolate_snapshot_data,
      isolate_snapshot_instructions, kernel_buffer, kernel_buffer_size);
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

  auto isolate_group_data = new IsolateGroupData(
      script_uri, packages_config, app_snapshot, isolate_run_app_snapshot);
  if (kernel_buffer != NULL) {
    if (parent_kernel_buffer) {
      isolate_group_data->SetKernelBufferAlreadyOwned(
          std::move(parent_kernel_buffer), kernel_buffer_size);
    } else {
      isolate_group_data->SetKernelBufferNewlyOwned(kernel_buffer,
                                                    kernel_buffer_size);
    }
  }

  Dart_Isolate isolate = NULL;

  IsolateData* isolate_data = nullptr;
#if !defined(DART_PRECOMPILED_RUNTIME)
  if (!isolate_run_app_snapshot && (isolate_snapshot_data == NULL)) {
    const uint8_t* platform_kernel_buffer = NULL;
    intptr_t platform_kernel_buffer_size = 0;
    dfe.LoadPlatform(&platform_kernel_buffer, &platform_kernel_buffer_size);
    if (platform_kernel_buffer == NULL) {
      platform_kernel_buffer = kernel_buffer;
      platform_kernel_buffer_size = kernel_buffer_size;
    }
    if (platform_kernel_buffer == NULL) {
#if defined(EXCLUDE_CFE_AND_KERNEL_PLATFORM)
      FATAL(
          "Binary built with --exclude-kernel-service. Cannot run"
          " from source.");
#else
      FATAL("platform_program cannot be NULL.");
#endif  // defined(EXCLUDE_CFE_AND_KERNEL_PLATFORM)
    }
    // TODO(sivachandra): When the platform program is unavailable, check if
    // application kernel binary is self contained or an incremental binary.
    // Isolate should be created only if it is a self contained kernel binary.
    isolate_data = new IsolateData(isolate_group_data);
    isolate = Dart_CreateIsolateGroupFromKernel(
        script_uri, name, platform_kernel_buffer, platform_kernel_buffer_size,
        flags, isolate_group_data, isolate_data, error);
  } else {
    isolate_data = new IsolateData(isolate_group_data);
    isolate = Dart_CreateIsolateGroup(script_uri, name, isolate_snapshot_data,
                                      isolate_snapshot_instructions, flags,
                                      isolate_group_data, isolate_data, error);
  }
#else
  isolate_data = new IsolateData(isolate_group_data);
  isolate = Dart_CreateIsolateGroup(script_uri, name, isolate_snapshot_data,
                                    isolate_snapshot_instructions, flags,
                                    isolate_group_data, isolate_data, error);
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

  Dart_Isolate created_isolate = NULL;
  if (isolate == NULL) {
    delete isolate_data;
    delete isolate_group_data;
  } else {
    created_isolate = IsolateSetupHelper(
        isolate, is_main_isolate, script_uri, packages_config,
        isolate_run_app_snapshot, flags, error, exit_code);
  }
  int64_t end = Dart_TimelineGetMicros();
  Dart_TimelineEvent("CreateIsolateGroupAndSetupHelper", start, end,
                     Dart_Timeline_Event_Duration, 0, NULL, NULL);
  return created_isolate;
}

#undef CHECK_RESULT

static Dart_Isolate CreateIsolateGroupAndSetup(const char* script_uri,
                                               const char* main,
                                               const char* package_root,
                                               const char* package_config,
                                               Dart_IsolateFlags* flags,
                                               void* callback_data,
                                               char** error) {
  // The VM should never call the isolate helper with a NULL flags.
  ASSERT(flags != NULL);
  ASSERT(flags->version == DART_FLAGS_CURRENT_VERSION);
  ASSERT(package_root == nullptr);

  bool dontneed_safe = true;
#if defined(DART_HOST_OS_LINUX)
  // This would also be true in Linux, except that Google3 overrides the default
  // ELF interpreter to one that apparently doesn't create proper mappings.
  dontneed_safe = false;
#elif defined(DEBUG)
  // If the snapshot isn't file-backed, madvise(DONT_NEED) is destructive.
  if (Options::force_load_elf_from_memory()) {
    dontneed_safe = false;
  }
#endif
  flags->snapshot_is_dontneed_safe = dontneed_safe;

  int exit_code = 0;
#if !defined(EXCLUDE_CFE_AND_KERNEL_PLATFORM)
  if (strcmp(script_uri, DART_KERNEL_ISOLATE_NAME) == 0) {
    return CreateAndSetupKernelIsolate(script_uri, package_config, flags, error,
                                       &exit_code);
  }
#endif  // !defined(EXCLUDE_CFE_AND_KERNEL_PLATFORM)

#if !defined(DART_PRECOMPILED_RUNTIME)
  if (strcmp(script_uri, DART_DEV_ISOLATE_NAME) == 0) {
    return CreateAndSetupDartDevIsolate(script_uri, package_config, flags,
                                        error, &exit_code);
  }
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

  if (strcmp(script_uri, DART_VM_SERVICE_ISOLATE_NAME) == 0) {
    return CreateAndSetupServiceIsolate(script_uri, package_config, flags,
                                        error, &exit_code);
  }

  bool is_main_isolate = false;
  return CreateIsolateGroupAndSetupHelper(is_main_isolate, script_uri, main,
                                          package_config, flags, callback_data,
                                          error, &exit_code);
}

static void OnIsolateShutdown(void* isolate_group_data, void* isolate_data) {
  Dart_EnterScope();
  Dart_Handle sticky_error = Dart_GetStickyError();
  if (!Dart_IsNull(sticky_error) && !Dart_IsFatalError(sticky_error)) {
    Syslog::PrintErr("%s\n", Dart_GetError(sticky_error));
  }
  Dart_ExitScope();
}

static void DeleteIsolateData(void* isolate_group_data, void* callback_data) {
  auto isolate_data = reinterpret_cast<IsolateData*>(callback_data);
  delete isolate_data;
}

static void DeleteIsolateGroupData(void* callback_data) {
  auto isolate_group_data = reinterpret_cast<IsolateGroupData*>(callback_data);
  delete isolate_group_data;
}

static const char* kStdoutStreamId = "Stdout";
static const char* kStderrStreamId = "Stderr";

static bool ServiceStreamListenCallback(const char* stream_id) {
  if (strcmp(stream_id, kStdoutStreamId) == 0) {
    SetCaptureStdout(true);
    return true;
  } else if (strcmp(stream_id, kStderrStreamId) == 0) {
    SetCaptureStderr(true);
    return true;
  }
  return false;
}

static void ServiceStreamCancelCallback(const char* stream_id) {
  if (strcmp(stream_id, kStdoutStreamId) == 0) {
    SetCaptureStdout(false);
  } else if (strcmp(stream_id, kStderrStreamId) == 0) {
    SetCaptureStderr(false);
  }
}

static bool FileModifiedCallback(const char* url, int64_t since) {
  if (strncmp(url, "file:///", 8) != 0) {
    // If it isn't a file on local disk, we don't know if it has been
    // modified.
    return true;
  }
  int64_t data[File::kStatSize];
  File::Stat(NULL, url + 7, data);
  if (data[File::kType] == File::kDoesNotExist) {
    return true;
  }
  bool modified = data[File::kModifiedTime] > since;
  return modified;
}

static void EmbedderInformationCallback(Dart_EmbedderInformation* info) {
  info->version = DART_EMBEDDER_INFORMATION_CURRENT_VERSION;
  info->name = "Dart VM";
  Process::GetRSSInformation(&(info->max_rss), &(info->current_rss));
}

#define CHECK_RESULT(result)                                                   \
  if (Dart_IsError(result)) {                                                  \
    const int exit_code = Dart_IsCompilationError(result)                      \
                              ? kCompilationErrorExitCode                      \
                              : kErrorExitCode;                                \
    ErrorExit(exit_code, "%s\n", Dart_GetError(result));                       \
  }

void RunMainIsolate(const char* script_name,
                    const char* package_config_override,
                    CommandLineOptions* dart_options) {
  if (script_name != NULL) {
    const char* base_name = strrchr(script_name, '/');
    if (base_name == NULL) {
      base_name = script_name;
    } else {
      base_name++;  // Skip '/'.
    }
    const intptr_t kMaxNameLength = 64;
    char name[kMaxNameLength];
    Utils::SNPrint(name, kMaxNameLength, "dart:%s", base_name);
    Platform::SetProcessName(name);
  }

  // Call CreateIsolateGroupAndSetup which creates an isolate and loads up
  // the specified application script.
  char* error = NULL;
  int exit_code = 0;
  Dart_IsolateFlags flags;
  Dart_IsolateFlagsInitialize(&flags);
  flags.is_system_isolate = Options::mark_main_isolate_as_system_isolate();
  bool dontneed_safe = true;
#if defined(DART_HOST_OS_LINUX)
  // This would also be true in Linux, except that Google3 overrides the default
  // ELF interpreter to one that apparently doesn't create proper mappings.
  dontneed_safe = false;
#elif defined(DEBUG)
  // If the snapshot isn't file-backed, madvise(DONT_NEED) is destructive.
  if (Options::force_load_elf_from_memory()) {
    dontneed_safe = false;
  }
#endif
  flags.snapshot_is_dontneed_safe = dontneed_safe;

  Dart_Isolate isolate = CreateIsolateGroupAndSetupHelper(
      /* is_main_isolate */ true, script_name, "main",
      Options::packages_file() == nullptr ? package_config_override
                                          : Options::packages_file(),
      &flags, NULL /* callback_data */, &error, &exit_code);

  if (isolate == NULL) {
    Syslog::PrintErr("%s\n", error);
    free(error);
    error = NULL;
    Process::TerminateExitCodeHandler();
    error = Dart_Cleanup();
    if (error != NULL) {
      Syslog::PrintErr("VM cleanup failed: %s\n", error);
      free(error);
    }
    dart::embedder::Cleanup();
    Platform::Exit((exit_code != 0) ? exit_code : kErrorExitCode);
  }
  main_isolate = isolate;

  Dart_EnterIsolate(isolate);
  ASSERT(isolate == Dart_CurrentIsolate());
  ASSERT(isolate != NULL);
  Dart_Handle result;

  Dart_EnterScope();

  auto isolate_group_data =
      reinterpret_cast<IsolateGroupData*>(Dart_IsolateGroupData(isolate));
  if (Options::gen_snapshot_kind() == kKernel) {
    if (vm_run_app_snapshot) {
      Syslog::PrintErr(
          "Cannot create a script snapshot from an app snapshot.\n");
      // The snapshot would contain references to the app snapshot instead of
      // the core snapshot.
      Platform::Exit(kErrorExitCode);
    }
    Snapshot::GenerateKernel(Options::snapshot_filename(), script_name,
                             isolate_group_data->resolved_packages_config());
  } else {
    // Lookup the library of the root script.
    Dart_Handle root_lib = Dart_RootLibrary();

#if !defined(DART_PRECOMPILED_RUNTIME)
    if (Options::compile_all()) {
      result = Dart_CompileAll();
      CHECK_RESULT(result);
    }
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

    if (Dart_IsNull(root_lib)) {
      ErrorExit(kErrorExitCode, "Unable to find root library for '%s'\n",
                script_name);
    }

    // Create a closure for the main entry point which is in the exported
    // namespace of the root library or invoke a getter of the same name
    // in the exported namespace and return the resulting closure.
    Dart_Handle main_closure =
        Dart_GetField(root_lib, Dart_NewStringFromCString("main"));
    CHECK_RESULT(main_closure);
    if (!Dart_IsClosure(main_closure)) {
      ErrorExit(kErrorExitCode, "Unable to find 'main' in root library '%s'\n",
                script_name);
    }

    // Call _startIsolate in the isolate library to enable dispatching the
    // initial startup message.
    const intptr_t kNumIsolateArgs = 2;
    Dart_Handle isolate_args[kNumIsolateArgs];
    isolate_args[0] = main_closure;                          // entryPoint
    isolate_args[1] = dart_options->CreateRuntimeOptions();  // args

    Dart_Handle isolate_lib =
        Dart_LookupLibrary(Dart_NewStringFromCString("dart:isolate"));
    result =
        Dart_Invoke(isolate_lib, Dart_NewStringFromCString("_startMainIsolate"),
                    kNumIsolateArgs, isolate_args);
    CHECK_RESULT(result);

    // Keep handling messages until the last active receive port is closed.
    result = Dart_RunLoop();
    // Generate an app snapshot after execution if specified.
    if (Options::gen_snapshot_kind() == kAppJIT) {
      if (!Dart_IsCompilationError(result)) {
        Snapshot::GenerateAppJIT(Options::snapshot_filename());
      }
    }
    CHECK_RESULT(result);
  }

  WriteDepsFile(isolate);

  Dart_ExitScope();

  // Shutdown the isolate.
  Dart_ShutdownIsolate();
}

#undef CHECK_RESULT

static bool CheckForInvalidPath(const char* path) {
  // TODO(zichangguo): "\\?\" is a prefix for paths on Windows.
  // Arguments passed are parsed as an URI. "\\?\" causes problems as a part
  // of URIs. This is a temporary workaround to prevent VM from crashing.
  // Issue: https://github.com/dart-lang/sdk/issues/42779
  if (strncmp(path, "\\\\?\\", 4) == 0) {
    Syslog::PrintErr("\\\\?\\ prefix is not supported");
    return false;
  }
  return true;
}

// Observatory assets are not included in a product build.
#if !defined(PRODUCT)
extern unsigned int observatory_assets_archive_len;
extern const uint8_t* observatory_assets_archive;

Dart_Handle GetVMServiceAssetsArchiveCallback() {
  uint8_t* decompressed = NULL;
  intptr_t decompressed_len = 0;
  Decompress(observatory_assets_archive, observatory_assets_archive_len,
             &decompressed, &decompressed_len);
  Dart_Handle tar_file =
      DartUtils::MakeUint8Array(decompressed, decompressed_len);
  // Free decompressed memory as it has been copied into a Dart array.
  free(decompressed);
  return tar_file;
}
#else   // !defined(PRODUCT)
static Dart_GetVMServiceAssetsArchive GetVMServiceAssetsArchiveCallback = NULL;
#endif  // !defined(PRODUCT)

void main(int argc, char** argv) {
  char* script_name = nullptr;
  // Allows the dartdev process to point to the desired package_config.
  char* package_config_override = nullptr;
  const int EXTRA_VM_ARGUMENTS = 10;
  CommandLineOptions vm_options(argc + EXTRA_VM_ARGUMENTS);
  CommandLineOptions dart_options(argc + EXTRA_VM_ARGUMENTS);
  bool print_flags_seen = false;
  bool verbose_debug_seen = false;

  // Perform platform specific initialization.
  if (!Platform::Initialize()) {
    Syslog::PrintErr("Initialization failed\n");
    Platform::Exit(kErrorExitCode);
  }

  // Save the console state so we can restore it at shutdown.
  Console::SaveConfig();

  // On Windows, the argv strings are code page encoded and not
  // utf8. We need to convert them to utf8.
  bool argv_converted = ShellUtils::GetUtf8Argv(argc, argv);

#if !defined(DART_PRECOMPILED_RUNTIME)
  // Processing of some command line flags directly manipulates dfe.
  Options::set_dfe(&dfe);
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

  // When running from the command line we assume that we are optimizing for
  // throughput, and therefore use a larger new gen semi space size and a faster
  // new gen growth factor unless others have been specified.
  if (kWordSize <= 4) {
    vm_options.AddArgument("--new_gen_semi_max_size=16");
  } else {
    vm_options.AddArgument("--new_gen_semi_max_size=32");
  }
  vm_options.AddArgument("--new_gen_growth_factor=4");

  AppSnapshot* app_snapshot = nullptr;
#if defined(DART_PRECOMPILED_RUNTIME)
  // If the executable binary contains the runtime together with an appended
  // snapshot, load and run that.
  // Any arguments passed to such an executable are meant for the actual
  // application so skip all Dart VM flag parsing.

  const size_t kPathBufSize = PATH_MAX + 1;
  char executable_path[kPathBufSize];
  if (Platform::ResolveExecutablePathInto(executable_path, kPathBufSize) > 0) {
    app_snapshot = Snapshot::TryReadAppendedAppSnapshotElf(executable_path);
    if (app_snapshot != nullptr) {
      script_name = argv[0];

      // Store the executable name.
      Platform::SetExecutableName(argv[0]);

      // Parse out options to be passed to dart main.
      for (int i = 1; i < argc; i++) {
        dart_options.AddArgument(argv[i]);
      }
    }
  }
#endif

  // Parse command line arguments.
  if (app_snapshot == nullptr) {
    bool success = Options::ParseArguments(
        argc, argv, vm_run_app_snapshot, &vm_options, &script_name,
        &dart_options, &print_flags_seen, &verbose_debug_seen);
    if (!success) {
      if (Options::help_option()) {
        Options::PrintUsage();
        Platform::Exit(0);
      } else if (Options::version_option()) {
        Options::PrintVersion();
        Platform::Exit(0);
      } else if (print_flags_seen) {
        // Will set the VM flags, print them out and then we exit as no
        // script was specified on the command line.
        char* error =
            Dart_SetVMFlags(vm_options.count(), vm_options.arguments());
        if (error != NULL) {
          Syslog::PrintErr("Setting VM flags failed: %s\n", error);
          free(error);
          Platform::Exit(kErrorExitCode);
        }
        Platform::Exit(0);
      } else {
        // This usage error case will only be invoked when
        // Options::disable_dart_dev() is false.
        Options::PrintUsage();
        Platform::Exit(kErrorExitCode);
      }
    }
  }

  DartUtils::SetEnvironment(Options::environment());

  if (Options::suppress_core_dump()) {
    Platform::SetCoreDumpResourceLimit(0);
  } else {
    InitializeCrashpadClient();
  }

  Loader::InitOnce();

  auto try_load_snapshots_lambda = [&](void) -> void {
    if (app_snapshot == nullptr) {
      // For testing purposes we add a flag to debug-mode to use the
      // in-memory ELF loader.
      const bool force_load_elf_from_memory =
          false DEBUG_ONLY(|| Options::force_load_elf_from_memory());
      app_snapshot =
          Snapshot::TryReadAppSnapshot(script_name, force_load_elf_from_memory);
    }
    if (app_snapshot != nullptr) {
      vm_run_app_snapshot = true;
      app_snapshot->SetBuffers(&vm_snapshot_data, &vm_snapshot_instructions,
                               &app_isolate_snapshot_data,
                               &app_isolate_snapshot_instructions);
    }
  };

  // At this point, script_name now points to a script if DartDev is disabled
  // or a valid file path was provided as the first non-flag argument.
  // Otherwise, script_name can be NULL if DartDev should be run.
  if (script_name != nullptr) {
    if (!CheckForInvalidPath(script_name)) {
      Platform::Exit(0);
    }
    try_load_snapshots_lambda();
  }

#if defined(DART_PRECOMPILED_RUNTIME)
  vm_options.AddArgument("--precompilation");
#endif
  // If we need to write an app-jit snapshot or a depfile, then add an exit
  // hook that writes the snapshot and/or depfile as appropriate.
  if ((Options::gen_snapshot_kind() == kAppJIT) ||
      (Options::depfile() != NULL)) {
    Process::SetExitHook(OnExitHook);
  }

  char* error = nullptr;
  if (!dart::embedder::InitOnce(&error)) {
    Syslog::PrintErr("Standalone embedder initialization failed: %s\n", error);
    free(error);
    Platform::Exit(kErrorExitCode);
  }

  error = Dart_SetVMFlags(vm_options.count(), vm_options.arguments());
  if (error != NULL) {
    Syslog::PrintErr("Setting VM flags failed: %s\n", error);
    free(error);
    Platform::Exit(kErrorExitCode);
  }

// Note: must read platform only *after* VM flags are parsed because
// they might affect how the platform is loaded.
#if !defined(DART_PRECOMPILED_RUNTIME)
  // Load vm_platform_strong.dill for dart:* source support.
  dfe.Init();
  dfe.set_verbosity(Options::verbosity_level());
  if (script_name != nullptr) {
    uint8_t* application_kernel_buffer = NULL;
    intptr_t application_kernel_buffer_size = 0;
    dfe.ReadScript(script_name, &application_kernel_buffer,
                   &application_kernel_buffer_size);
    if (application_kernel_buffer != NULL) {
      // Since we loaded the script anyway, save it.
      dfe.set_application_kernel_buffer(application_kernel_buffer,
                                        application_kernel_buffer_size);
      Options::dfe()->set_use_dfe();
    }
  }
#endif

  // Initialize the Dart VM.
  Dart_InitializeParams init_params;
  memset(&init_params, 0, sizeof(init_params));
  init_params.version = DART_INITIALIZE_PARAMS_CURRENT_VERSION;
  init_params.vm_snapshot_data = vm_snapshot_data;
  init_params.vm_snapshot_instructions = vm_snapshot_instructions;
  init_params.create_group = CreateIsolateGroupAndSetup;
  init_params.initialize_isolate = OnIsolateInitialize;
  init_params.shutdown_isolate = OnIsolateShutdown;
  init_params.cleanup_isolate = DeleteIsolateData;
  init_params.cleanup_group = DeleteIsolateGroupData;
  init_params.file_open = DartUtils::OpenFile;
  init_params.file_read = DartUtils::ReadFile;
  init_params.file_write = DartUtils::WriteFile;
  init_params.file_close = DartUtils::CloseFile;
  init_params.entropy_source = DartUtils::EntropySource;
  init_params.get_service_assets = GetVMServiceAssetsArchiveCallback;
#if !defined(DART_PRECOMPILED_RUNTIME)
  init_params.start_kernel_isolate =
      dfe.UseDartFrontend() && dfe.CanUseDartFrontend();
#else
  init_params.start_kernel_isolate = false;
#endif

  error = Dart_Initialize(&init_params);
  if (error != NULL) {
    dart::embedder::Cleanup();
    Syslog::PrintErr("VM initialization failed: %s\n", error);
    free(error);
    Platform::Exit(kErrorExitCode);
  }

  Dart_SetServiceStreamCallbacks(&ServiceStreamListenCallback,
                                 &ServiceStreamCancelCallback);
  Dart_SetFileModifiedCallback(&FileModifiedCallback);
  Dart_SetEmbedderInformationCallback(&EmbedderInformationCallback);
  bool ran_dart_dev = false;
  bool should_run_user_program = true;
#if !defined(DART_PRECOMPILED_RUNTIME)
  if (DartDevIsolate::should_run_dart_dev() && !Options::disable_dart_dev() &&
      Options::gen_snapshot_kind() == SnapshotKind::kNone) {
    DartDevIsolate::DartDev_Result dartdev_result = DartDevIsolate::RunDartDev(
        CreateIsolateGroupAndSetup, &package_config_override, &script_name,
        &dart_options);
    ASSERT(dartdev_result != DartDevIsolate::DartDev_Result_Unknown);
    ran_dart_dev = true;
    should_run_user_program =
        (dartdev_result == DartDevIsolate::DartDev_Result_Run);
    if (should_run_user_program) {
      try_load_snapshots_lambda();
    }
  }
#endif  // !defined(DART_PRECOMPILED_RUNTIME)

  if (should_run_user_program) {
    if (!Dart_IsPrecompiledRuntime() && Snapshot::IsAOTSnapshot(script_name)) {
      Syslog::PrintErr(
          "%s is an AOT snapshot and should be run with 'dartaotruntime'\n",
          script_name);
      Platform::Exit(kErrorExitCode);
    } else {
      // Run the main isolate until we aren't told to restart.
      RunMainIsolate(script_name, package_config_override, &dart_options);
    }
  }

  // Terminate process exit-code handler.
  Process::TerminateExitCodeHandler();

  error = Dart_Cleanup();
  if (error != NULL) {
    Syslog::PrintErr("VM cleanup failed: %s\n", error);
    free(error);
  }
  const intptr_t global_exit_code = Process::GlobalExitCode();
  dart::embedder::Cleanup();

  delete app_snapshot;
  free(app_script_uri);
  if (ran_dart_dev && script_name != nullptr) {
    free(script_name);
  }

  // Free copied argument strings if converted.
  if (argv_converted) {
    for (int i = 0; i < argc; i++) {
      free(argv[i]);
    }
  }

  // Free environment if any.
  Options::DestroyEnvironment();

  Platform::Exit(global_exit_code);
}

}  // namespace bin
}  // namespace dart

int main(int argc, char** argv) {
  dart::bin::main(argc, argv);
  UNREACHABLE();
}