Fix bug 6467:

runtime/vm/dart.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 "vm/dart.h"
 
 #include "vm/dart_api_state.h"
 #include "vm/flags.h"
 #include "vm/freelist.h"
 #include "vm/handles.h"
@@ skipping 30 matching lines @@
   void VisitObject(RawObject* obj) {
     // RawInstruction objects are premarked on allocation.
     if (!obj->IsMarked()) {
       obj->SetMarkBit();
     }
   }
 };
 
 
 // TODO(turnidge): We should add a corresponding Dart::Cleanup.
-bool Dart::InitOnce(Dart_IsolateCreateCallback create,
+const char* Dart::InitOnce(Dart_IsolateCreateCallback create,
                     Dart_IsolateInterruptCallback interrupt,
                     Dart_IsolateShutdownCallback shutdown) {
   // TODO(iposva): Fix race condition here.
   if (vm_isolate_ != NULL || !Flags::Initialized()) {
-    return false;
+    return "VM already initialized.";
   }
   OS::InitOnce();
   VirtualMemory::InitOnce();
   Isolate::InitOnce();
   PortMap::InitOnce();
   FreeListElement::InitOnce();
   Api::InitOnce();
   // Create the VM isolate and finish the VM initialization.
   ASSERT(thread_pool_ == NULL);
   thread_pool_ = new ThreadPool();
   {
     ASSERT(vm_isolate_ == NULL);
     ASSERT(Flags::Initialized());
     vm_isolate_ = Isolate::Init("vm-isolate");
     StackZone zone(vm_isolate_);
     HandleScope handle_scope(vm_isolate_);
     Heap::Init(vm_isolate_);
     ObjectStore::Init(vm_isolate_);
     Object::InitOnce();
     StubCode::InitOnce();
     Scanner::InitOnce();
     Symbols::InitOnce(vm_isolate_);
     CPUFeatures::InitOnce();
 #if defined(TARGET_ARCH_IA32) || defined(TARGET_ARCH_X64)
     // Dart VM requires at least SSE3.
-    if (!CPUFeatures::sse3_supported()) return false;
+    if (!CPUFeatures::sse3_supported()) {
+      return "SSE3 is required.";
+    }
 #endif
     PremarkingVisitor premarker(vm_isolate_);
     vm_isolate_->heap()->IterateOldObjects(&premarker);
     vm_isolate_->heap()->WriteProtect(true);
   }
   Isolate::SetCurrent(NULL);  // Unregister the VM isolate from this thread.
   Isolate::SetCreateCallback(create);
   Isolate::SetInterruptCallback(interrupt);
   Isolate::SetShutdownCallback(shutdown);
-  return true;
+  return NULL;
 }
 
 
 Isolate* Dart::CreateIsolate(const char* name_prefix) {
   // Create a new isolate.
   Isolate* isolate = Isolate::Init(name_prefix);
   ASSERT(isolate != NULL);
   return isolate;
 }
 
@@ skipping 80 matching lines @@
   isolate->Shutdown();
   delete isolate;
 
   Dart_IsolateShutdownCallback callback = Isolate::ShutdownCallback();
   if (callback != NULL) {
     (callback)(callback_data);
   }
 }
 
 }  // namespace dart