flutter_flutter/engine/src/flutter/runtime/dart_vm_initializer.cc

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "flutter/runtime/dart_vm_initializer.h"

#include <atomic>

#include "flutter/fml/logging.h"
#include "flutter/fml/synchronization/shared_mutex.h"
#include "flutter/fml/trace_event.h"
#include "flutter/lib/ui/ui_dart_state.h"
#include "flutter/lib/ui/window/platform_configuration.h"
#include "third_party/tonic/converter/dart_converter.h"
#include "third_party/tonic/logging/dart_error.h"

#include "dart_timestamp_provider.h"

namespace {
// Tracks whether Dart has been initialized and if it is safe to call Dart
// APIs.
static std::atomic<bool> gDartInitialized;

void LogUnhandledException(Dart_Handle exception_handle,
                           Dart_Handle stack_trace_handle) {
  const std::string error =
      tonic::StdStringFromDart(Dart_ToString(exception_handle));
  const std::string stack_trace =
      tonic::StdStringFromDart(Dart_ToString(stack_trace_handle));

  auto state = flutter::UIDartState::Current();
  if (state && state->unhandled_exception_callback()) {
    auto callback = state->unhandled_exception_callback();
    if (callback(error, stack_trace)) {
      return;
    }
  }

  // Either the exception handler was not set or it could not handle the
  // error, just log the exception.
  FML_LOG(ERROR) << "Unhandled Exception: " << error << std::endl
                 << stack_trace;
}

void ReportUnhandledException(Dart_Handle exception_handle,
                              Dart_Handle stack_trace_handle) {
  // Hooks.dart will call the error handler on PlatformDispatcher if it is
  // not null. If it is null, returns false, fall into the !handled branch
  // below and log.
  // If it is not null, defer to the return value of that closure
  // to determine whether to report via logging.
  bool handled = false;
  auto state = flutter::UIDartState::Current();
  if (!state || !state->platform_configuration()) {
    LogUnhandledException(exception_handle, stack_trace_handle);
    return;
  }
  auto on_error = state->platform_configuration()->on_error();
  if (on_error) {
    FML_DCHECK(!Dart_IsNull(on_error));
    Dart_Handle args[2];
    args[0] = exception_handle;
    args[1] = stack_trace_handle;
    Dart_Handle on_error_result = Dart_InvokeClosure(on_error, 2, args);

    // An exception was thrown by the exception handler.
    if (Dart_IsError(on_error_result)) {
      LogUnhandledException(Dart_ErrorGetException(on_error_result),
                            Dart_ErrorGetStackTrace(on_error_result));

      handled = false;
    } else {
      handled = tonic::DartConverter<bool>::FromDart(on_error_result);
    }
    if (!handled) {
      LogUnhandledException(exception_handle, stack_trace_handle);
    }
  }
}
}  // namespace

void DartVMInitializer::Initialize(Dart_InitializeParams* params,
                                   bool enable_timeline_event_handler,
                                   bool trace_systrace) {
  FML_DCHECK(!gDartInitialized);

  char* error = Dart_Initialize(params);
  if (error) {
    FML_LOG(FATAL) << "Error while initializing the Dart VM: " << error;
    ::free(error);
  } else {
    gDartInitialized = true;
  }

  if (enable_timeline_event_handler) {
    if (!trace_systrace) {
      // Systrace on all platforms except Fuchsia ignores the timestamp provided
      // here. On Android in particular, calls to get the system clock show up
      // in profiles.
      // Fuchsia does not use the TraceSetTimelineMicrosSource.
      fml::tracing::TraceSetTimelineMicrosSource(Dart_TimelineGetMicros);
    } else {
      fml::tracing::TraceSetTimelineMicrosSource(
          []() -> int64_t { return -1; });
    }
    fml::tracing::TraceSetTimelineEventHandler(LogDartTimelineEvent);
  }

  fml::TimePoint::SetClockSource(flutter::DartTimelineTicksSinceEpoch);
  tonic::SetUnhandledExceptionReporter(&ReportUnhandledException);
}

void DartVMInitializer::Cleanup() {
  FML_DCHECK(gDartInitialized);

  // Dart_TimelineEvent is unsafe during a concurrent call to Dart_Cleanup
  // because Dart_Cleanup will destroy the timeline recorder.  Clear the
  // initialized flag so that future calls to LogDartTimelineEvent will not
  // call Dart_TimelineEvent.
  //
  // Note that this is inherently racy.  If a thread sees that gDartInitialized
  // is set and proceeds to call Dart_TimelineEvent shortly before another
  // thread calls Dart_Cleanup, then the Dart_TimelineEvent call may crash
  // if Dart_Cleanup deletes the timeline before Dart_TimelineEvent completes.
  // In practice this is unlikely because Dart_Cleanup does significant other
  // work before deleting the timeline.
  //
  // The engine can not safely guard Dart_Cleanup and LogDartTimelineEvent with
  // a lock due to the risk of deadlocks.  Dart_Cleanup waits for various
  // Dart-owned threads to shut down.  If one of those threads invokes an engine
  // callback that calls LogDartTimelineEvent while the Dart_Cleanup thread owns
  // the lock, then Dart_Cleanup would deadlock.
  gDartInitialized = false;

  char* error = Dart_Cleanup();
  if (error) {
    FML_LOG(FATAL) << "Error while cleaning up the Dart VM: " << error;
    ::free(error);
  }
}

void DartVMInitializer::LogDartTimelineEvent(const char* label,
                                             int64_t timestamp0,
                                             int64_t timestamp1_or_async_id,
                                             Dart_Timeline_Event_Type type,
                                             intptr_t argument_count,
                                             const char** argument_names,
                                             const char** argument_values) {
  if (gDartInitialized) {
    Dart_TimelineEvent(label, timestamp0, timestamp1_or_async_id, type,
                       argument_count, argument_names, argument_values);
  }
}