Do not allow external strings in old pointer space.

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5912 matching lines @@
 
 
 i::Handle<i::String> NewExternalAsciiStringHandle(i::Isolate* isolate,
       v8::String::ExternalAsciiStringResource* resource) {
   i::Handle<i::String> result =
       isolate->factory()->NewExternalStringFromAscii(resource);
   return result;
 }
 
 
+bool RedirectToExternalString(i::Isolate* isolate,
+                              i::Handle<i::String> parent,
+                              i::Handle<i::String> external) {
+  if (parent->IsConsString()) {
+    i::Handle<i::ConsString> cons = i::Handle<i::ConsString>::cast(parent);
+    cons->set_first(*external);
+    cons->set_second(isolate->heap()->empty_string());
+  } else {
+    ASSERT(parent->IsSlicedString());
+    i::Handle<i::SlicedString> slice = i::Handle<i::SlicedString>::cast(parent);
+    slice->set_parent(*external);
+    slice->set_offset(0);
+  }
+  return true;
+}
+
+
 Local<String> v8::String::NewExternal(
       v8::String::ExternalStringResource* resource) {
   i::Isolate* isolate = i::Isolate::Current();
   EnsureInitializedForIsolate(isolate, "v8::String::NewExternal()");
   LOG_API(isolate, "String::NewExternal");
   ENTER_V8(isolate);
   CHECK(resource && resource->data());
   i::Handle<i::String> result = NewExternalStringHandle(isolate, resource);
   isolate->heap()->external_string_table()->AddString(*result);
   return Utils::ToLocal(result);
 }
 
 
 bool v8::String::MakeExternal(v8::String::ExternalStringResource* resource) {
   i::Handle<i::String> obj = Utils::OpenHandle(this);
   i::Isolate* isolate = obj->GetIsolate();
   if (IsDeadCheck(isolate, "v8::String::MakeExternal()")) return false;
   if (i::StringShape(*obj).IsExternalTwoByte()) {
     return false;  // Already an external string.
   }
   ENTER_V8(isolate);
   if (isolate->string_tracker()->IsFreshUnusedString(obj)) {
     return false;
   }
   if (isolate->heap()->IsInGCPostProcessing()) {
     return false;
   }
   CHECK(resource && resource->data());
-  bool result = obj->MakeExternal(resource);
-  if (result && !obj->IsInternalizedString()) {
-    isolate->heap()->external_string_table()->AddString(*obj);
+
+  bool result;
+  i::Handle<i::String> external;
+  if (isolate->heap()->old_pointer_space()->Contains(*obj)) {
+    // We do not allow external strings in the old pointer space.  Instead of
+    // converting the string in-place, we keep the cons/sliced string and
+    // point it to a newly-allocated external string.
+    external = NewExternalStringHandle(isolate, resource);
+    result = RedirectToExternalString(isolate, obj, external);
+  } else {
+    result = obj->MakeExternal(resource);
+    external = obj;
+  }
+
+  ASSERT(external->IsExternalString());
+  if (result && !external->IsInternalizedString()) {
+    isolate->heap()->external_string_table()->AddString(*external);
   }
   return result;
 }
 
 
 Local<String> v8::String::NewExternal(
       v8::String::ExternalAsciiStringResource* resource) {
   i::Isolate* isolate = i::Isolate::Current();
   EnsureInitializedForIsolate(isolate, "v8::String::NewExternal()");
   LOG_API(isolate, "String::NewExternal");
@@ skipping 14 matching lines @@
     return false;  // Already an external string.
   }
   ENTER_V8(isolate);
   if (isolate->string_tracker()->IsFreshUnusedString(obj)) {
     return false;
   }
   if (isolate->heap()->IsInGCPostProcessing()) {
     return false;
   }
   CHECK(resource && resource->data());
-  bool result = obj->MakeExternal(resource);
-  if (result && !obj->IsInternalizedString()) {
-    isolate->heap()->external_string_table()->AddString(*obj);
+
+  bool result;
+  i::Handle<i::String> external;
+  if (isolate->heap()->old_pointer_space()->Contains(*obj)) {
+    // We do not allow external strings in the old pointer space.  Instead of
+    // converting the string in-place, we keep the cons/sliced string and
+    // point it to a newly-allocated external string.
+    external = NewExternalAsciiStringHandle(isolate, resource);
+    result = RedirectToExternalString(isolate, obj, external);
+  } else {
+    result = obj->MakeExternal(resource);
+    external = obj;
+  }
+
+  ASSERT(external->IsExternalString());
+  if (result && !external->IsInternalizedString()) {
+    isolate->heap()->external_string_table()->AddString(*external);
   }
   return result;
 }
 
 
 bool v8::String::CanMakeExternal() {
   if (!internal::FLAG_clever_optimizations) return false;
   i::Handle<i::String> obj = Utils::OpenHandle(this);
   i::Isolate* isolate = obj->GetIsolate();
   if (IsDeadCheck(isolate, "v8::String::CanMakeExternal()")) return false;
@@ skipping 2041 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   return callback(info);
 }
 
 
 } }  // namespace v8::internal