Ensure deoptimizing frames have a valid pc marker before deferred materialization.

runtime/vm/code_generator.cc

 // Copyright (c) 2013, 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/code_generator.h"
 
 #include "vm/assembler.h"
 #include "vm/ast.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
@@ skipping 1775 matching lines @@
 END_LEAF_RUNTIME_ENTRY
 
 
 // This is the last step in the deoptimization, GC can occur.
 // Returns number of bytes to remove from the expression stack of the
 // bottom-most deoptimized frame. Those arguments were artificially injected
 // under return address to keep them discoverable by GC that can occur during
 // materialization phase.
 DEFINE_RUNTIME_ENTRY(DeoptimizeMaterialize, 0) {
 #if !defined(DART_PRECOMPILED_RUNTIME)
+#if defined(DEBUG)
+  {
+    // We may rendezvous for a safepoint at entry or GC from the allocations
+    // below. Check the stack is walkable.
+    StackFrameIterator frames_iterator(StackFrameIterator::kValidateFrames);
+    StackFrame* frame = frames_iterator.NextFrame();
+    while (frame != NULL) {
+      frame = frames_iterator.NextFrame();
+    }
+  }
+#endif
   DeoptContext* deopt_context = isolate->deopt_context();
   intptr_t deopt_arg_count = deopt_context->MaterializeDeferredObjects();
   isolate->set_deopt_context(NULL);
   delete deopt_context;
 
   // Return value tells deoptimization stub to remove the given number of bytes
   // from the stack.
   arguments.SetReturn(Smi::Handle(Smi::New(deopt_arg_count * kWordSize)));
 #else
   UNREACHABLE();
@@ skipping 68 matching lines @@
   const intptr_t elm_size = old_data.ElementSizeInBytes();
   const TypedData& new_data =
       TypedData::Handle(TypedData::New(cid, new_size, Heap::kOld));
   TypedData::Copy(new_data, 0, old_data, 0, old_size * elm_size);
   typed_data_cell.SetAt(0, new_data);
   arguments.SetReturn(new_data);
 }
 
 
 }  // namespace dart