FIx crash in disassembler: check that an addrs is tagged before testing it to be part of the heap.

runtime/vm/disassembler_x64.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/disassembler.h"
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_IA32.
 #if defined(TARGET_ARCH_X64)
 #include "platform/utils.h"
 #include "vm/allocation.h"
@@ skipping 781 matching lines @@
   OS::SNPrint(chars, len, format, full_class_name);
   return chars;
 }
 
 
 void DisassemblerX64::AppendAddressToBuffer(uint8_t* addr_byte_ptr) {
   NoGCScope no_gc;
   uword addr = reinterpret_cast<uword>(addr_byte_ptr);
   AppendToBuffer("%#"Px"", addr);
   // Try to print as heap object or stub name
-  if (!Isolate::Current()->heap()->CodeContains(addr) &&
+  if (((addr & kSmiTagMask) == kHeapObjectTag) &&
+      !Isolate::Current()->heap()->CodeContains(addr) &&
       Isolate::Current()->heap()->Contains(addr - kHeapObjectTag)) {
     Object& obj = Object::Handle(reinterpret_cast<RawObject*>(addr));
     if (obj.IsArray()) {
       const Array& arr = Array::CheckedHandle(obj.raw());
       intptr_t len = arr.Length();
       if (len > 5) len = 5;  // Print a max of 5 elements.
       AppendToBuffer("  Array[");
       int i = 0;
       while (i < len) {
         obj = arr.At(i);
@@ skipping 1045 matching lines @@
                                   human_buffer,
                                   sizeof(human_buffer),
                                   pc);
     pc += instruction_length;
   }
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64