Issue 5552 - use strict mode for all JS in libadblocklus

src/JsEngine.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
@@ skipping 30 matching lines @@
 
   void CheckTryCatch(const v8::TryCatch& tryCatch)
   {
     if (tryCatch.HasCaught())
       throw AdblockPlus::JsError(tryCatch.Exception(), tryCatch.Message());
   }
 
   class V8Initializer
   {
     V8Initializer()
-      : platform(v8::platform::CreateDefaultPlatform())
-    {
+      : platform{nullptr}
+    {
+      std::string cmd = "--use_strict";
+      v8::V8::SetFlagsFromString(cmd.c_str(), cmd.length());
+      platform = v8::platform::CreateDefaultPlatform();
       v8::V8::InitializePlatform(platform);
       v8::V8::Initialize();

[anton, 2017/08/22 08:22:33]

in v8_initiliazer.cc in chromium `v8::V8::Initialize();` is invoked after flags
set:
  v8::V8::InitializePlatform(vp);

  ...
  if (IsolateHolder::kStrictMode == mode) {
    static const char use_strict[] = "--use_strict";
    v8::V8::SetFlagsFromString(use_strict, sizeof(use_strict) - 1);
  }
  ...
  v8::V8::Initialize();

did/can you make sure the order you've used is not important here?

[sergei, 2017/08/22 10:52:18]

Good catch! Actually this particular flag is used only when a compilation of a
script is called, namely for us it's when JsEngine::Evaluate is called, so the
current order is fine. Actually I have taken the order from
https://github.com/v8/v8/blob/master/src/d8.cc. However, in both d8.cc (call of
Shell::SetOptions) and in the code of v8 I see that some flags should be set
before v8::V8::Initialize();. So, to simplify the catching of potential bugs
when we decide to add new flags I have moved setting of the flags even before
creation of a platform, as it's done in d8.cc.

-      std::string cmd = "--use_strict";
-      v8::V8::SetFlagsFromString(cmd.c_str(), cmd.length());
     }
 
     ~V8Initializer()
     {
       v8::V8::Dispose();
       v8::V8::ShutdownPlatform();
       delete platform;
     }
     v8::Platform* platform;
   public:
@@ skipping 232 matching lines @@
     list.push_back(JsValue(shared_from_this(), arguments[i]));
   return list;
 }
 
 void AdblockPlus::JsEngine::SetGlobalProperty(const std::string& name,
                                               const AdblockPlus::JsValue& value)
 {
   auto global = GetGlobalObject();
   global.SetProperty(name, value);
 }