Added generic singletons facility

<sigh> yes, I know - but we have them - may as well make them consistent and safer

include/internal/catch_registry_hub.cpp

@@ -14,6 +14,7 @@
 #include "catch_exception_translator_registry.h"
 #include "catch_tag_alias_registry.h"
 #include "catch_startup_exception_registry.h"
+#include "catch_singletons.hpp"
 
 namespace Catch {
 
@@ -84,6 +85,7 @@ namespace Catch {
         return *getTheRegistryHub();
     }
     void cleanUp() {
+        cleanupSingletons();
         delete getTheRegistryHub();
         getTheRegistryHub() = nullptr;
         cleanUpContext();

include/internal/catch_singletons.cpp

@@ -0,0 +1,36 @@
+/*
+ *  Created by Phil Nash on 15/6/2018.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include "catch_singletons.hpp"
+
+#include <vector>
+
+namespace Catch {
+
+    namespace {
+        static auto getSingletons() -> std::vector<ISingleton*>*& {
+            static std::vector<ISingleton*>* g_singletons = nullptr;
+            if( !g_singletons )
+                g_singletons = new std::vector<ISingleton*>();
+            return g_singletons;
+        }
+    }
+
+    ISingleton::~ISingleton() {}
+
+    void addSingleton(ISingleton* singleton ) {
+        getSingletons()->push_back( singleton );
+    }
+    void cleanupSingletons() {
+        auto& singletons = getSingletons();
+        for( auto singleton : *singletons )
+            delete singleton;
+        delete singletons;
+        singletons = nullptr;
+    }
+
+} // namespace Catch

include/internal/catch_singletons.hpp

@@ -0,0 +1,44 @@
+/*
+ *  Created by Phil Nash on 15/6/2018.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+#ifndef TWOBLUECUBES_CATCH_SINGLETONS_HPP_INCLUDED
+#define TWOBLUECUBES_CATCH_SINGLETONS_HPP_INCLUDED
+
+namespace Catch {
+
+    struct ISingleton {
+        virtual ~ISingleton();
+    };
+
+
+    void addSingleton( ISingleton* singleton );
+    void cleanupSingletons();
+
+
+    template<typename SingletonImplT, typename InterfaceT = SingletonImplT, typename MutableInterfaceT = InterfaceT>
+    class Singleton : SingletonImplT, public ISingleton {
+
+        static auto getInternal() -> Singleton* {
+            static Singleton* s_instance = nullptr;
+            if( !s_instance ) {
+                s_instance = new Singleton;
+                addSingleton( s_instance );
+            }
+            return s_instance;
+        }
+
+    public:
+        static auto get() -> InterfaceT const& {
+            return *getInternal();
+        }
+        static auto getMutable() -> MutableInterfaceT& {
+            return *getInternal();
+        }
+    };
+
+} // namespace Catch
+
+#endif // TWOBLUECUBES_CATCH_SINGLETONS_HPP_INCLUDED

projects/CMakeLists.txt

@@ -117,6 +117,7 @@ set(INTERNAL_HEADERS
         ${HEADER_DIR}/internal/catch_section.h
         ${HEADER_DIR}/internal/catch_section_info.h
         ${HEADER_DIR}/internal/catch_session.h
+        ${HEADER_DIR}/internal/catch_singletons.hpp
         ${HEADER_DIR}/internal/catch_startup_exception_registry.h
         ${HEADER_DIR}/internal/catch_stream.h
         ${HEADER_DIR}/internal/catch_stringref.h
@@ -183,6 +184,7 @@ set(IMPL_SOURCES
         ${HEADER_DIR}/internal/catch_section.cpp
         ${HEADER_DIR}/internal/catch_section_info.cpp
         ${HEADER_DIR}/internal/catch_session.cpp
+        ${HEADER_DIR}/internal/catch_singletons.cpp
         ${HEADER_DIR}/internal/catch_startup_exception_registry.cpp
         ${HEADER_DIR}/internal/catch_stream.cpp
         ${HEADER_DIR}/internal/catch_stringref.cpp