Verify the symbol table contents before and after all...

src/objects.h

 // Copyright 2006-2008 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 423 matching lines @@
 // If bit 7 is clear, the low-order 2 bits indicate the representation
 // of the string.
 const uint32_t kStringRepresentationMask = 0x03;
 enum StringRepresentationTag {
   kSeqStringTag = 0x0,
   kConsStringTag = 0x1,
   kSlicedStringTag = 0x2,
   kExternalStringTag = 0x3
 };
 
+
+// A ConsString with an empty string as the right side is a candidate
+// for being shortcut by the garbage collector unless it is a
+// symbol. It's not common to have non-flat symbols, so we do not
+// shortcut them thereby avoiding turning symbols into strings. See
+// heap.cc and mark-compact.cc.
+STATIC_ASSERT(kNotStringTag != 0 && kSymbolTag != 0);
+const uint32_t kShortcutTypeMask =
+    kIsNotStringMask |
+    kIsSymbolMask |
+    kStringRepresentationMask;
+const uint32_t kShortcutTypeTag = kConsStringTag;
+
+
 enum InstanceType {
   SHORT_SYMBOL_TYPE = kShortStringTag | kSymbolTag | kSeqStringTag,
   MEDIUM_SYMBOL_TYPE = kMediumStringTag | kSymbolTag | kSeqStringTag,
   LONG_SYMBOL_TYPE = kLongStringTag | kSymbolTag | kSeqStringTag,
   SHORT_ASCII_SYMBOL_TYPE =
       kShortStringTag | kAsciiStringTag | kSymbolTag | kSeqStringTag,
   MEDIUM_ASCII_SYMBOL_TYPE =
       kMediumStringTag | kAsciiStringTag | kSymbolTag | kSeqStringTag,
   LONG_ASCII_SYMBOL_TYPE =
       kLongStringTag | kAsciiStringTag | kSymbolTag | kSeqStringTag,
@@ skipping 3861 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_