Fix null-termination bug in Stacktrace::ToCString.

runtime/vm/object.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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
@@ skipping 13018 matching lines @@
     total_len += len;
     chars = isolate->current_zone()->Alloc<char>(len + 1);
     OS::SNPrint(chars, (len + 1), kFormat,
                 i,
                 function_name.ToCString(),
                 url.ToCString(),
                 line, column);
     frame_strings.Add(chars);
   }
 
-  // Now concatentate the frame descriptions into a single C string.
+  // Now concatenate the frame descriptions into a single C string.
   chars = isolate->current_zone()->Alloc<char>(total_len + 1);
   intptr_t index = 0;
   for (intptr_t i = 0; i < frame_strings.length(); i++) {
     index += OS::SNPrint((chars + index),
                          (total_len + 1 - index),
                          "%s",
                          frame_strings[i]);
   }
+  chars[total_len] = '\0';
   return chars;
 }
 
 
 void JSRegExp::set_pattern(const String& pattern) const {
   StorePointer(&raw_ptr()->pattern_, pattern.raw());
 }
 
 
 void JSRegExp::set_num_bracket_expressions(intptr_t value) const {
@@ skipping 102 matching lines @@
   }
   return result.raw();
 }
 
 
 const char* WeakProperty::ToCString() const {
   return "_WeakProperty";
 }
 
 }  // namespace dart