Capturing for loop variables correctly

runtime/vm/code_generator.cc

 // Copyright (c) 2011, 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/code_index_table.h"
 #include "vm/code_patcher.h"
 #include "vm/compiler.h"
 #include "vm/dart_api_impl.h"
@@ skipping 273 matching lines @@
 // Arg0: number of variables.
 // Return value: newly allocated context.
 DEFINE_RUNTIME_ENTRY(AllocateContext, 1) {
   CHECK_STACK_ALIGNMENT;
   ASSERT(arguments.Count() == kAllocateContextRuntimeEntry.argument_count());
   const Smi& num_variables = Smi::CheckedHandle(arguments.At(0));
   arguments.SetReturn(Context::Handle(Context::New(num_variables.Value())));
 }
 
 
+// Make a copy of the given context, including the values of the captured
+// variables.
+// Arg0: the context to be cloned.
+// Return value: newly allocated context.
+DEFINE_RUNTIME_ENTRY(CloneContext, 1) {
+  CHECK_STACK_ALIGNMENT;
+  ASSERT(arguments.Count() == kCloneContextRuntimeEntry.argument_count());
+  const Context& ctx = Context::CheckedHandle(arguments.At(0));
+  Context& cloned_ctx = Context::Handle(Context::New(ctx.num_variables()));
+  cloned_ctx.set_parent(Context::Handle(ctx.parent()));
+  for (int i = 0; i < ctx.num_variables(); i++) {
+    cloned_ctx.SetAt(i, Instance::Handle(ctx.At(i)));
+  }
+  arguments.SetReturn(cloned_ctx);
+}
+
+
 // Check that the given instance is an instance of the given type.
 // Tested instance may not be null, because the null test is inlined.
 // Arg0: instance being checked.
 // Arg1: type.
 // Arg2: type arguments of the instantiator of the type.
 // Return value: true or false.
 DEFINE_RUNTIME_ENTRY(Instanceof, 3) {
   ASSERT(arguments.Count() == kInstanceofRuntimeEntry.argument_count());
   const Instance& instance = Instance::CheckedHandle(arguments.At(0));
   const Type& type = Type::CheckedHandle(arguments.At(1));
@@ skipping 660 matching lines @@
       }
     }
   }
   // The cache is null terminated, therefore the loop above should never
   // terminate by itself.
   UNREACHABLE();
   return Code::null();
 }
 
 }  // namespace dart