Replaces LongJump with LongJumpScope.

runtime/vm/longjump.h

 // 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.
 
 #ifndef VM_LONGJUMP_H_
 #define VM_LONGJUMP_H_
 
 #include <setjmp.h>
 
 #include "vm/allocation.h"
+#include "vm/isolate.h"
 
 namespace dart {
 
 class Error;
 
-class LongJump : public ValueObject {
+class LongJumpScope : public ValueObject {
  public:
-  LongJump() : top_(NULL) { }
+  LongJumpScope() : top_(NULL), base_(Isolate::Current()->long_jump_base()) {
+    Isolate::Current()->set_long_jump_base(this);
+  }
+
+  ~LongJumpScope() {
+    Isolate::Current()->set_long_jump_base(base_);
+  }
 
   jmp_buf* Set();
   void Jump(int value, const Error& error);
 
   // Would it be safe to use this longjump?
   //
   // Checks to make sure that the jump would not cross Dart frames.
   bool IsSafeToJump();
 
  private:
   jmp_buf environment_;
   StackResource* top_;
+  LongJumpScope* base_;
 
-  DISALLOW_COPY_AND_ASSIGN(LongJump);
+  DISALLOW_COPY_AND_ASSIGN(LongJumpScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_LONGJUMP_H_