VM: Fix memory leaks during isolate spawning

runtime/lib/isolate.cc

 // 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 "include/dart_native_api.h"
 #include "platform/assert.h"
 #include "vm/bootstrap_natives.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart.h"
 #include "vm/dart_api_impl.h"
@@ skipping 221 matching lines @@
     func = Closure::Cast(closure).function();
     if (func.IsImplicitClosureFunction() && func.is_static()) {
 #if defined(DEBUG)
       Context& ctx = Context::Handle();
       ctx = Closure::Cast(closure).context();
       ASSERT(ctx.num_variables() == 0);
 #endif
       // Get the parent function so that we get the right function name.
       func = func.parent_function();
 
+      bool fatal_errors = fatalErrors.IsNull() ? true : fatalErrors.value();
+      Dart_Port on_exit_port = onExit.IsNull() ? ILLEGAL_PORT : onExit.Id();
+      Dart_Port on_error_port = onError.IsNull() ? ILLEGAL_PORT : onError.Id();
+
+      // We first try to serialize the message.  In case the message is not
+      // serializable this will throw an exception.
+      SerializedObjectBuffer message_buffer;
+      {
+        MessageWriter writer(message_buffer.data_buffer(), &malloc_allocator,
+                             &malloc_deallocator,
+                             /* can_send_any_object = */ true,
+                             message_buffer.data_length());
+        writer.WriteMessage(message);
+      }
+
       const char* utf8_package_root =
           packageRoot.IsNull() ? NULL : String2UTF8(packageRoot);
       const char* utf8_package_config =
           packageConfig.IsNull() ? NULL : String2UTF8(packageConfig);

[kustermann, 2017/01/23 19:14:55]

These two allocated strings were leaked when the code in [IsolateSpawnState] was
throwing.

 
-      bool fatal_errors = fatalErrors.IsNull() ? true : fatalErrors.value();
-      Dart_Port on_exit_port = onExit.IsNull() ? ILLEGAL_PORT : onExit.Id();
-      Dart_Port on_error_port = onError.IsNull() ? ILLEGAL_PORT : onError.Id();
-
       IsolateSpawnState* state = new IsolateSpawnState(
           port.Id(), isolate->origin_id(), isolate->init_callback_data(),
-          String2UTF8(script_uri), func, message,
+          String2UTF8(script_uri), func, &message_buffer,
           isolate->spawn_count_monitor(), isolate->spawn_count(),
           utf8_package_root, utf8_package_config, paused.value(), fatal_errors,
           on_exit_port, on_error_port);
       ThreadPool::Task* spawn_task = new SpawnIsolateTask(state);
 
       isolate->IncrementSpawnCount();
       if (FLAG_i_like_slow_isolate_spawn) {
         // We block the parent isolate while the child isolate loads.
         Isolate* saved = Isolate::Current();
         Thread::ExitIsolate();
@@ skipping 79 matching lines @@
   if (Dart::vm_snapshot_kind() == Snapshot::kAppAOT) {
     const Array& args = Array::Handle(Array::New(1));
     args.SetAt(
         0,
         String::Handle(String::New(
             "Isolate.spawnUri is not supported when using AOT compilation")));
     Exceptions::ThrowByType(Exceptions::kUnsupported, args);
     UNREACHABLE();
   }
 
+  bool fatal_errors = fatalErrors.IsNull() ? true : fatalErrors.value();
+  Dart_Port on_exit_port = onExit.IsNull() ? ILLEGAL_PORT : onExit.Id();
+  Dart_Port on_error_port = onError.IsNull() ? ILLEGAL_PORT : onError.Id();
+
+  // We first try to serialize the arguments and the message.  In case the
+  // arguments or the message are not serializable this will throw an exception.
+  SerializedObjectBuffer arguments_buffer;
+  SerializedObjectBuffer message_buffer;
+  {
+    MessageWriter writer(
+        arguments_buffer.data_buffer(), &malloc_allocator, &malloc_deallocator,
+        /* can_send_any_object = */ false, arguments_buffer.data_length());
+    writer.WriteMessage(args);
+  }
+  {
+    MessageWriter writer(
+        message_buffer.data_buffer(), &malloc_allocator, &malloc_deallocator,
+        /* can_send_any_object = */ false, arguments_buffer.data_length());
+    writer.WriteMessage(message);
+  }
+
   // Canonicalize the uri with respect to the current isolate.
   const Library& root_lib =
       Library::Handle(isolate->object_store()->root_library());
   char* error = NULL;
   const char* canonical_uri = CanonicalizeUri(thread, root_lib, uri, &error);
   if (canonical_uri == NULL) {
     const String& msg = String::Handle(String::New(error));
     ThrowIsolateSpawnException(msg);
   }
 
   const char* utf8_package_root =
       packageRoot.IsNull() ? NULL : String2UTF8(packageRoot);
   const char* utf8_package_config =
       packageConfig.IsNull() ? NULL : String2UTF8(packageConfig);
 
-  bool fatal_errors = fatalErrors.IsNull() ? true : fatalErrors.value();
-  Dart_Port on_exit_port = onExit.IsNull() ? ILLEGAL_PORT : onExit.Id();
-  Dart_Port on_error_port = onError.IsNull() ? ILLEGAL_PORT : onError.Id();
-
   IsolateSpawnState* state = new IsolateSpawnState(
       port.Id(), isolate->init_callback_data(), canonical_uri,
-      utf8_package_root, utf8_package_config, args, message,
-      isolate->spawn_count_monitor(), isolate->spawn_count(), paused.value(),
-      fatal_errors, on_exit_port, on_error_port);
+      utf8_package_root, utf8_package_config, &arguments_buffer,
+      &message_buffer, isolate->spawn_count_monitor(), isolate->spawn_count(),
+      paused.value(), fatal_errors, on_exit_port, on_error_port);
 
   // If we were passed a value then override the default flags state for
   // checked mode.
   if (!checked.IsNull()) {
     bool val = checked.value();
     Dart_IsolateFlags* flags = state->isolate_flags();
     flags->enable_asserts = val;
     flags->enable_type_checks = val;
   }
 
@@ skipping 48 matching lines @@
   uint8_t* data = NULL;
   MessageWriter writer(&data, &malloc_allocator, &malloc_deallocator, false);
   writer.WriteMessage(msg);
 
   PortMap::PostMessage(new Message(port.Id(), data, writer.BytesWritten(),
                                    Message::kOOBPriority));
   return Object::null();
 }
 
 }  // namespace dart