Do checks when receiving external string resources through the API.

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 4772 matching lines @@
   return result;
 }
 
 
 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->IsSymbol()) {
     isolate->heap()->external_string_table()->AddString(*obj);
   }
   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");
   ENTER_V8(isolate);
+  CHECK(resource && resource->data());
   i::Handle<i::String> result = NewExternalAsciiStringHandle(isolate, resource);
   isolate->heap()->external_string_table()->AddString(*result);
   return Utils::ToLocal(result);
 }
 
 
 bool v8::String::MakeExternal(
     v8::String::ExternalAsciiStringResource* 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->IsSymbol()) {
     isolate->heap()->external_string_table()->AddString(*obj);
   }
   return result;
 }
 
 
 bool v8::String::CanMakeExternal() {
   if (!internal::FLAG_clever_optimizations) return false;
@@ skipping 1664 matching lines @@
 
   v->VisitPointers(blocks_.first(), first_block_limit_);
 
   for (int i = 1; i < blocks_.length(); i++) {
     v->VisitPointers(blocks_[i], &blocks_[i][kHandleBlockSize]);
   }
 }
 
 
 } }  // namespace v8::internal