VM: Fix memory leaks during isolate spawning

runtime/vm/snapshot.h

 // 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.
 
 #ifndef RUNTIME_VM_SNAPSHOT_H_
 #define RUNTIME_VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 642 matching lines @@
     // Make room for recording snapshot buffer size.
     stream_.set_current(stream_.buffer() + Snapshot::kHeaderSize);
   }
 
   void FillHeader(Snapshot::Kind kind) {
     int64_t* data = reinterpret_cast<int64_t*>(stream_.buffer());
     data[Snapshot::kLengthIndex] = stream_.bytes_written();
     data[Snapshot::kSnapshotFlagIndex] = kind;
   }
 
-  void FreeBuffer() { dealloc_(stream_.buffer()); }
+  void FreeBuffer() {
+    dealloc_(stream_.buffer());
+    stream_.set_buffer(NULL);
+  }
 
  private:
   WriteStream stream_;
   DeAlloc dealloc_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(BaseWriter);
 };
 
 
 class ForwardList {
@@ skipping 295 matching lines @@
   // Writes a partial snapshot of the script.
   void WriteScriptSnapshot(const Library& lib);
 
  private:
   ForwardList forward_list_;
 
   DISALLOW_COPY_AND_ASSIGN(ScriptSnapshotWriter);
 };
 
 
+class SerializedObjectBuffer : public StackResource {
+ public:
+  SerializedObjectBuffer()
+      : StackResource(Thread::Current()),
+        object_data_(NULL),
+        object_length_(0) {}
+
+  virtual ~SerializedObjectBuffer() { free(object_data_); }
+
+  void TakeBuffer(uint8_t** out_data, intptr_t* out_length) {

[rmacnak, 2017/01/24 03:54:53]

Similar existing methods in the VM are called StealBuffer.

[kustermann, 2017/01/24 09:02:00]

Done.

+    *out_data = object_data_;
+    *out_length = object_length_;
+
+    object_data_ = NULL;
+    object_length_ = 0;
+  }
+
+  uint8_t** data_buffer() { return &object_data_; }
+  intptr_t* data_length() { return &object_length_; }
+
+ private:
+  uint8_t* object_data_;
+  intptr_t object_length_;
+};
+
+
 class MessageWriter : public SnapshotWriter {
  public:
   static const intptr_t kInitialSize = 512;
   MessageWriter(uint8_t** buffer,
                 ReAlloc alloc,
                 DeAlloc dealloc,
-                bool can_send_any_object);
+                bool can_send_any_object,
+                intptr_t* buffer_len = NULL);
   ~MessageWriter() {}
 
   void WriteMessage(const Object& obj);
 
  private:
   ForwardList forward_list_;
+  intptr_t* buffer_len_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageWriter);
 };
 
 
 // An object pointer visitor implementation which writes out
 // objects to a snap shot.
 class SnapshotWriterVisitor : public ObjectPointerVisitor {
  public:
   SnapshotWriterVisitor(SnapshotWriter* writer, bool as_references)
       : ObjectPointerVisitor(Isolate::Current()),
         writer_(writer),
         as_references_(as_references) {}
 
   virtual void VisitPointers(RawObject** first, RawObject** last);
 
  private:
   SnapshotWriter* writer_;
   bool as_references_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_SNAPSHOT_H_