1 files changed, 13 insertions, 11 deletions

diff --git a/src/google/protobuf/dynamic_message.cc b/src/google/protobuf/dynamic_message.cc
index d6bde495..ee8113e3 100644
--- a/src/google/protobuf/dynamic_message.cc
+++ b/src/google/protobuf/dynamic_message.cc
@@ -77,13 +77,14 @@
 #include <google/protobuf/generated_message_util.h>
 #include <google/protobuf/generated_message_reflection.h>
 #include <google/protobuf/arenastring.h>
+#include <google/protobuf/extension_set.h>
+#include <google/protobuf/map_field.h>
 #include <google/protobuf/map_field_inl.h>
+#include <google/protobuf/map_type_handler.h>
 #include <google/protobuf/reflection_ops.h>
 #include <google/protobuf/repeated_field.h>
-#include <google/protobuf/map_type_handler.h>
-#include <google/protobuf/extension_set.h>
 #include <google/protobuf/wire_format.h>
-#include <google/protobuf/map_field.h>
+
 
 namespace google {
 namespace protobuf {
@@ -239,6 +240,7 @@ class DynamicMessage : public Message {
     // looking back at this field. This would assume details about the
     // implementation of scoped_ptr.
     const DynamicMessage* prototype;
+    int weak_field_map_offset;  // The offset for the weak_field_map;
 
     TypeInfo() : prototype(NULL) {}
 
@@ -323,7 +325,6 @@ void DynamicMessage::SharedCtor() {
   // constructor.)
 
   const Descriptor* descriptor = type_info_->type;
-
   // Initialize oneof cases.
   for (int i = 0 ; i < descriptor->oneof_decl_count(); ++i) {
     new (OffsetToPointer(type_info_->oneof_case_offset + sizeof(uint32) * i))
@@ -336,7 +337,6 @@ void DynamicMessage::SharedCtor() {
   if (type_info_->extensions_offset != -1) {
     new (OffsetToPointer(type_info_->extensions_offset)) ExtensionSet;
   }
-
   for (int i = 0; i < descriptor->field_count(); i++) {
     const FieldDescriptor* field = descriptor->field(i);
     void* field_ptr = OffsetToPointer(type_info_->offsets[i]);
@@ -537,7 +537,6 @@ void DynamicMessage::CrossLinkPrototypes() {
   for (int i = 0; i < descriptor->field_count(); i++) {
     const FieldDescriptor* field = descriptor->field(i);
     void* field_ptr = OffsetToPointer(type_info_->offsets[i]);
-
     if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
         !field->is_repeated()) {
       // For fields with message types, we need to cross-link with the
@@ -694,6 +693,7 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
   // All the fields.
   //
   // TODO(b/31226269):  Optimize the order of fields to minimize padding.
+  int num_weak_fields = 0;
   for (int i = 0; i < type->field_count(); i++) {
     // Make sure field is aligned to avoid bus errors.
     // Oneof fields do not use any space.
@@ -717,6 +717,8 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
   type_info->internal_metadata_offset = size;
   size += sizeof(InternalMetadataWithArena);
 
+  type_info->weak_field_map_offset = -1;
+
   // Align the final size to make sure no clever allocators think that
   // alignment is not necessary.
   type_info->size = size;
@@ -738,7 +740,6 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
     }
   }
   size = AlignOffset(size);
-
   // Allocate the prototype + oneof fields.
   void* base = operator new(size);
   memset(base, 0, size);
@@ -752,7 +753,7 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
   type_info->prototype = static_cast<DynamicMessage*>(base);
   DynamicMessage* prototype = new(base) DynamicMessage(type_info);
 
-  if (type->oneof_decl_count() > 0) {
+  if (type->oneof_decl_count() > 0 || num_weak_fields > 0) {
     // Construct default oneof instance.
     ConstructDefaultOneofInstance(type_info->type,
                                   type_info->offsets.get(),
@@ -767,7 +768,8 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
       type_info->internal_metadata_offset,
       type_info->extensions_offset,
       type_info->oneof_case_offset,
-      type_info->size};
+      type_info->size,
+      type_info->weak_field_map_offset};
 
   type_info->reflection.reset(new GeneratedMessageReflection(
       type_info->type, schema, type_info->pool, this));
@@ -781,12 +783,12 @@ const Message* DynamicMessageFactory::GetPrototypeNoLock(
 void DynamicMessageFactory::ConstructDefaultOneofInstance(
     const Descriptor* type,
     const uint32 offsets[],
-    void* default_oneof_instance) {
+    void* default_oneof_or_weak_instance) {
   for (int i = 0; i < type->oneof_decl_count(); i++) {
     for (int j = 0; j < type->oneof_decl(i)->field_count(); j++) {
       const FieldDescriptor* field = type->oneof_decl(i)->field(j);
       void* field_ptr = reinterpret_cast<uint8*>(
-          default_oneof_instance) + offsets[field->index()];
+          default_oneof_or_weak_instance) + offsets[field->index()];
       switch (field->cpp_type()) {
 #define HANDLE_TYPE(CPPTYPE, TYPE)                                      \
         case FieldDescriptor::CPPTYPE_##CPPTYPE:                        \