Noissue - [emscripten] Replace sprintf() usage by safe alternatives

compiled/filter/ActiveFilter.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include <cstdio>
 
 #include "ActiveFilter.h"
 #include "../StringScanner.h"
 
 namespace
 {
   const DependentString DEFAULT_DOMAIN(u""_str);
 
   OwnedString to_string(unsigned int i)
   {
-    char buffer[11];
-    int len = sprintf(buffer, "%u", i);
+    const std::size_t BUFFER_SIZE = 11;
+    char buffer[BUFFER_SIZE];
+    int len = snprintf(buffer, BUFFER_SIZE, "%u", i);
 
     OwnedString result(len);

[hub, 2017/04/06 10:31:23]

From `man snprintf`
So we shouldn't use len to initialise result that way.
Nor as a counter for iterating through the buffer.

[Wladimir Palant, 2017/04/06 15:14:40]

We have the same issue in the subscription classes. I think we should just avoid
unnecessary buffers by writing our own conversion function that can deal with
wide chars.

     for (String::size_type i = 0; i < len; i++)
       result[i] = buffer[i];
     return result;
   }
 }
 
 ActiveFilter::ActiveFilter(Type type, const String& text, bool ignoreTrailingDot)
     : Filter(type, text), mDisabled(false), mHitCount(0), mLastHit(0),
       mIgnoreTrailingDot(ignoreTrailingDot)
 {
@@ skipping 155 matching lines @@
     result.append(u'\n');
   }
   if (mLastHit)
   {
     result.append(u"lastHit="_str);
     result.append(to_string(mLastHit));
     result.append(u'\n');
   }
   return result;
 }