From e1a09e48c45d3198ab84a76ff6373c3e462a6c4c Mon Sep 17 00:00:00 2001
From: Artem Pavlenko <artem@mapnik.org>
Date: Thu, 9 Mar 2023 21:06:55 +0000
Subject: [PATCH] c++11 style singleton implementation - singleton_cxx11<T>

---
 include/mapnik/datasource_cache.hpp          |  7 +++----
 include/mapnik/debug.hpp                     |  2 +-
 include/mapnik/factory.hpp                   |  2 +-
 include/mapnik/font_engine_freetype.hpp      |  6 +++---
 include/mapnik/mapped_memory_cache.hpp       |  6 +++---
 include/mapnik/marker_cache.hpp              |  4 ++--
 include/mapnik/text/formatting/registry.hpp  |  2 +-
 include/mapnik/text/placements/registry.hpp  |  2 +-
 include/mapnik/util/singleton.hpp            | 18 ++++++++++++++++++
 plugins/input/postgis/connection_manager.hpp |  7 +++----
 src/datasource_cache.cpp                     |  2 +-
 src/font_engine_freetype.cpp                 |  2 +-
 src/mapped_memory_cache.cpp                  |  2 +-
 13 files changed, 39 insertions(+), 23 deletions(-)

diff --git a/include/mapnik/datasource_cache.hpp b/include/mapnik/datasource_cache.hpp
index 4e321c9ad..38a5ad918 100644
--- a/include/mapnik/datasource_cache.hpp
+++ b/include/mapnik/datasource_cache.hpp
@@ -41,11 +41,10 @@ class datasource;
 class parameters;
 class PluginInfo;
 
-class MAPNIK_DECL datasource_cache : public singleton<datasource_cache, CreateStatic>,
+class MAPNIK_DECL datasource_cache : public singleton_cxx11<datasource_cache>,
                                      private util::noncopyable
 {
-    friend class CreateStatic<datasource_cache>;
-
+    friend class singleton_cxx11<datasource_cache>;
   public:
     bool plugin_registered(const std::string& plugin_name) const;
     std::vector<std::string> plugin_names() const;
@@ -66,7 +65,7 @@ class MAPNIK_DECL datasource_cache : public singleton<datasource_cache, CreateSt
     mutable std::recursive_mutex instance_mutex_;
 };
 
-extern template class MAPNIK_DECL singleton<datasource_cache, CreateStatic>;
+extern template class MAPNIK_DECL singleton_cxx11<datasource_cache>;
 
 } // namespace mapnik
 
diff --git a/include/mapnik/debug.hpp b/include/mapnik/debug.hpp
index 161bb8298..4ce37f081 100644
--- a/include/mapnik/debug.hpp
+++ b/include/mapnik/debug.hpp
@@ -45,7 +45,7 @@ namespace mapnik {
 // Global logger class that holds the configuration of severity, format
 // and file/console redirection.
 
-class MAPNIK_DECL logger : public singleton<logger, CreateStatic>,
+class MAPNIK_DECL logger : public singleton_cxx11<logger>,
                            private util::noncopyable
 {
   public:
diff --git a/include/mapnik/factory.hpp b/include/mapnik/factory.hpp
index 680b5dbe0..c9751c9cb 100644
--- a/include/mapnik/factory.hpp
+++ b/include/mapnik/factory.hpp
@@ -33,7 +33,7 @@
 namespace mapnik {
 
 template<typename product_type, typename key_type, typename... Args>
-class factory : public singleton<factory<product_type, key_type, Args...>>
+class factory : public singleton_cxx11<factory<product_type, key_type, Args...>>
 {
   private:
     using product_creator = product_type* (*)(Args...);
diff --git a/include/mapnik/font_engine_freetype.hpp b/include/mapnik/font_engine_freetype.hpp
index d2c0d034c..033b8bcc1 100644
--- a/include/mapnik/font_engine_freetype.hpp
+++ b/include/mapnik/font_engine_freetype.hpp
@@ -50,10 +50,10 @@ using face_set_ptr = std::unique_ptr<font_face_set>;
 class font_face;
 using face_ptr = std::shared_ptr<font_face>;
 
-class MAPNIK_DECL freetype_engine : public singleton<freetype_engine, CreateUsingNew>,
+class MAPNIK_DECL freetype_engine : public singleton_cxx11<freetype_engine>,
                                     private util::noncopyable
 {
-    friend class CreateUsingNew<freetype_engine>;
+    friend class singleton_cxx11<freetype_engine>;
     friend class Map;
 
   public:
@@ -132,7 +132,7 @@ class MAPNIK_DECL face_manager
 };
 
 using face_manager_freetype = face_manager;
-extern template class MAPNIK_DECL singleton<freetype_engine, CreateUsingNew>;
+extern template class MAPNIK_DECL singleton_cxx11<freetype_engine>;
 } // namespace mapnik
 
 #endif // MAPNIK_FONT_ENGINE_FREETYPE_HPP
diff --git a/include/mapnik/mapped_memory_cache.hpp b/include/mapnik/mapped_memory_cache.hpp
index 4b3e01797..3ab74425d 100644
--- a/include/mapnik/mapped_memory_cache.hpp
+++ b/include/mapnik/mapped_memory_cache.hpp
@@ -48,10 +48,10 @@ namespace mapnik {
 
 using mapped_region_ptr = std::shared_ptr<boost::interprocess::mapped_region>;
 
-class MAPNIK_DECL mapped_memory_cache : public singleton<mapped_memory_cache, CreateStatic>,
+class MAPNIK_DECL mapped_memory_cache : public singleton_cxx11<mapped_memory_cache>,
                                         private util::noncopyable
 {
-    friend class CreateStatic<mapped_memory_cache>;
+    friend class singleton_cxx11<mapped_memory_cache>;
     std::unordered_map<std::string, mapped_region_ptr> cache_;
 
   public:
@@ -68,7 +68,7 @@ class MAPNIK_DECL mapped_memory_cache : public singleton<mapped_memory_cache, Cr
     void clear();
 };
 
-extern template class MAPNIK_DECL singleton<mapped_memory_cache, CreateStatic>;
+extern template class MAPNIK_DECL singleton_cxx11<mapped_memory_cache>;
 
 } // namespace mapnik
 
diff --git a/include/mapnik/marker_cache.hpp b/include/mapnik/marker_cache.hpp
index 5fb2c929f..7b9ba89cb 100644
--- a/include/mapnik/marker_cache.hpp
+++ b/include/mapnik/marker_cache.hpp
@@ -36,10 +36,10 @@ namespace mapnik {
 
 struct marker;
 
-class MAPNIK_DECL marker_cache : public singleton<marker_cache, CreateUsingNew>,
+class MAPNIK_DECL marker_cache : public singleton_cxx11<marker_cache>,
                                  private util::noncopyable
 {
-    friend class CreateUsingNew<marker_cache>;
+    friend class singleton_cxx11<marker_cache>;
 
   private:
     marker_cache();
diff --git a/include/mapnik/text/formatting/registry.hpp b/include/mapnik/text/formatting/registry.hpp
index c7b5dfdaa..423967915 100644
--- a/include/mapnik/text/formatting/registry.hpp
+++ b/include/mapnik/text/formatting/registry.hpp
@@ -37,7 +37,7 @@ namespace formatting {
 
 using from_xml_function_ptr = node_ptr (*)(xml_node const&, fontset_map const&);
 
-class registry : public singleton<registry, CreateStatic>,
+class registry : public singleton_cxx11<registry>,
                  private util::noncopyable
 {
   public:
diff --git a/include/mapnik/text/placements/registry.hpp b/include/mapnik/text/placements/registry.hpp
index 1967a923b..918d903ce 100644
--- a/include/mapnik/text/placements/registry.hpp
+++ b/include/mapnik/text/placements/registry.hpp
@@ -36,7 +36,7 @@ namespace placements {
 
 using from_xml_function_ptr = text_placements_ptr (*)(xml_node const&, fontset_map const&, bool);
 
-class registry : public singleton<registry, CreateStatic>,
+class registry : public singleton_cxx11<registry>,
                  private util::noncopyable
 {
   public:
diff --git a/include/mapnik/util/singleton.hpp b/include/mapnik/util/singleton.hpp
index 897fcee69..7e920c8e1 100644
--- a/include/mapnik/util/singleton.hpp
+++ b/include/mapnik/util/singleton.hpp
@@ -62,6 +62,22 @@ class CreateStatic
     static void destroy(volatile T* obj) { obj->~T(); }
 };
 
+template<typename T>
+class singleton_cxx11
+{
+public:
+    static T& instance()
+    {
+        static T instance;
+        return instance;
+    }
+protected:
+#ifdef MAPNIK_THREADSAFE
+    static std::mutex mutex_;
+#endif
+};
+
+
 #ifdef __GNUC__
 template<typename T, template<typename U> class CreatePolicy = CreateStatic>
 class MAPNIK_DECL singleton
@@ -130,6 +146,8 @@ class singleton
 #ifdef MAPNIK_THREADSAFE
 template<typename T, template<typename U> class CreatePolicy>
 std::mutex singleton<T, CreatePolicy>::mutex_;
+template<typename T>
+std::mutex singleton_cxx11<T>::mutex_;
 #endif
 template<typename T, template<typename U> class CreatePolicy>
 std::atomic<T*> singleton<T, CreatePolicy>::pInstance_;
diff --git a/plugins/input/postgis/connection_manager.hpp b/plugins/input/postgis/connection_manager.hpp
index d8014d0bf..a5b005d28 100644
--- a/plugins/input/postgis/connection_manager.hpp
+++ b/plugins/input/postgis/connection_manager.hpp
@@ -37,9 +37,8 @@
 #include <string>
 #include <memory>
 
-using mapnik::CreateStatic;
 using mapnik::Pool;
-using mapnik::singleton;
+using mapnik::singleton_cxx11;
 
 template<typename T>
 class ConnectionCreator
@@ -110,13 +109,13 @@ class ConnectionCreator
     boost::optional<std::string> application_name_;
 };
 
-class ConnectionManager : public singleton<ConnectionManager, CreateStatic>
+class ConnectionManager : public singleton_cxx11<ConnectionManager>
 {
   public:
     using PoolType = Pool<Connection, ConnectionCreator>;
 
   private:
-    friend class CreateStatic<ConnectionManager>;
+    friend class singleton_cxx11<ConnectionManager>;
 
     using ContType = std::map<std::string, std::shared_ptr<PoolType>>;
     using HolderType = std::shared_ptr<Connection>;
diff --git a/src/datasource_cache.cpp b/src/datasource_cache.cpp
index 5539e3fc6..5857bfcd7 100644
--- a/src/datasource_cache.cpp
+++ b/src/datasource_cache.cpp
@@ -44,7 +44,7 @@ MAPNIK_DISABLE_WARNING_POP
 
 namespace mapnik {
 
-template class singleton<datasource_cache, CreateStatic>;
+template class singleton_cxx11<datasource_cache>;
 
 extern datasource_ptr create_static_datasource(parameters const& params);
 extern std::vector<std::string> get_static_datasource_names();
diff --git a/src/font_engine_freetype.cpp b/src/font_engine_freetype.cpp
index c905aaedd..05411893b 100644
--- a/src/font_engine_freetype.cpp
+++ b/src/font_engine_freetype.cpp
@@ -48,7 +48,7 @@ MAPNIK_DISABLE_WARNING_POP
 #include <stdexcept>
 
 namespace mapnik {
-template class MAPNIK_DECL singleton<freetype_engine, CreateUsingNew>;
+template class MAPNIK_DECL singleton_cxx11<freetype_engine>;
 
 bool freetype_engine::is_font_file(std::string const& file_name)
 {
diff --git a/src/mapped_memory_cache.cpp b/src/mapped_memory_cache.cpp
index 8da68a1c5..828c1b3e5 100644
--- a/src/mapped_memory_cache.cpp
+++ b/src/mapped_memory_cache.cpp
@@ -37,7 +37,7 @@ MAPNIK_DISABLE_WARNING_POP
 
 namespace mapnik {
 
-template class singleton<mapped_memory_cache, CreateStatic>;
+template class singleton_cxx11<mapped_memory_cache>;
 
 void mapped_memory_cache::clear()
 {