From f1aa0df4c3bb90faba7d9203312f043fd59dec9d Mon Sep 17 00:00:00 2001
From: Vlad Zolotarov <vladz@cloudius-systems.com>
Date: Mon, 1 Jun 2015 11:31:49 +0300
Subject: [PATCH] class_registrator: ensure the static member initialization
 order

There was a possibility for initialization disorder of static member _classes
and its usage in another static class.

Defining the _classes inside the static method that is called when it's accessed ensures
the proper initialization (aka "standard trick", quoting Avi ;)).

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
---
 utils/class_registrator.hh | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/utils/class_registrator.hh b/utils/class_registrator.hh
index 31c4ed1e85..a6158fab7b 100644
--- a/utils/class_registrator.hh
+++ b/utils/class_registrator.hh
@@ -14,20 +14,22 @@ public:
 template<typename BaseType, typename... Args>
 class class_registry {
     using creator_type = std::function<std::unique_ptr<BaseType>(Args...)>;
-    static std::unordered_map<sstring, creator_type> _classes;
 public:
     static void register_class(sstring name, creator_type creator);
     template<typename T>
     static void register_class(sstring name);
     static std::unique_ptr<BaseType> create(const sstring& name, Args...);
+
+    static std::unordered_map<sstring, creator_type>& classes() {
+        static std::unordered_map<sstring, creator_type> _classes;
+
+        return _classes;
+    }
 };
 
-template<typename BaseType, typename... Args>
-std::unordered_map<sstring, typename class_registry<BaseType, Args...>::creator_type> class_registry<BaseType, Args...>::_classes;
-
 template<typename BaseType, typename... Args>
 void class_registry<BaseType, Args...>::register_class(sstring name, class_registry<BaseType, Args...>::creator_type creator) {
-    _classes.emplace(name, std::move(creator));
+    classes().emplace(name, std::move(creator));
 }
 
 template<typename BaseType, typename... Args>
@@ -50,8 +52,8 @@ struct class_registrator {
 
 template<typename BaseType, typename... Args>
 std::unique_ptr<BaseType> class_registry<BaseType, Args...>::create(const sstring& name, Args... args) {
-    auto it = _classes.find(name);
-    if (it == _classes.end()) {
+    auto it = classes().find(name);
+    if (it == classes().end()) {
         throw no_such_class(sstring("unable to find class '") + name + sstring("'"));
     }
     return it->second(args...);