From 6c3e1aee4328e423da77efc527921cbba40b3a39 Mon Sep 17 00:00:00 2001
From: Mindaugas <fraillt@gmail.com>
Date: Tue, 8 Jan 2019 16:00:02 +0200
Subject: [PATCH] removed anonymous namespace from PolymorphicBaseClass as it
 only works on clang, and is not standard compliant

---
 CHANGELOG.md                                  | 34 ++++++++++++++++---
 .../bitsery/ext/utils/polymorphism_utils.h    | 18 ++++------
 2 files changed, 37 insertions(+), 15 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0a3788c..3a51756 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,12 +5,38 @@
 E.g. `int64_t money = 8000;` will only use 2 bytes, instead of 8. **CompactValueAsObject** allows to use `ext()` overload, without specifying size of underlying type and sets BUFFER_OVERFLOW error if value doesn't fit in underlying type during deserialization.
 
 ### Improvements
-* improved **PolymorphicContext** for registering base class hierarchies from different translation units.
-Previously there was only one symbol for `PolymorphicBaseClass`, but now a primary template for this type lives in anonymous namespace, so each translation unit could get their own symbol.
-`registerBasesList` was modified, so that where invocation happens, it will bind to correct symbol for `PolymorphicBaseClass`.
+* improved **PolymorphicContext**, allows to extend already registered hierarchy in one translation unit, using different type other than `PolymorphicBaseClass` to avoid symbol collision between translation units or libraries.
+`registerBasesList` was modified, so that it could accept user defined type (instead of `PolymorphicBaseClass`) that is used to declare hierarchy, by default it is `PolymorphicBaseClass`.
 This introduced breaking change, for those who used this syntax (`registerBasesList<MySerializer, Shape>({})`) during registration.
 It is encouraged to define helper type, that could be used for registering hierarchy for serialization and deserialization [example](examples/smart_pointers_with_polymorphism.cpp).
-* **PolymorphicContext** also get optional method `registerSingleBaseBranch`, that allows manually register hierarchies, but it is not recommended as it is error-prone.
+`This is only relevant then you want to use **PolymorphicContext** between different translation units or libraries`.
+```cpp
+//libA
+namespace bitsery {
+    namespace ext {
+        template<>
+        struct PolymorphicBaseClass<Shape> : PolymorphicDerivedClasses<Circle, Rectangle> {};
+    }
+}
+using MyPolymorphicClassesForRegistering = bitsery::ext::PolymorphicClassesList<Shape>;
+...
+    ctx.registerBasesList<MySerializer>(MyPolymorphicClassesForRegistering{}).
+
+//otherLib
+struct MySquare: Shape {...}
+//now it must define different type (exactly the same as PolymorphicBaseClass) to declare hierarchy
+template<typename TBase>
+struct MyHierarchy {
+    using Childs = PolymorphicClassesList<>;
+};
+
+template <>
+struct MyHierarchy<Shape>: bitsery::ext::bitsery::ext::PolymorphicClassesList<MySquare> {};
+...
+//notice that we pass MyHierarchy as second argument
+    ctx.registerBasesList<MySerializer, MyHierarchy>(MyPolymorphicClassesForRegistering{}).
+```
+* **PolymorphicContext** also get optional method `registerSingleBaseBranch`, that allows manually register hierarchies, this might be more convenient when using you need to register in different translation units (or libraries), but it is error-prone.
 
 # [4.3.0](https://github.com/fraillt/bitsery/compare/v4.2.1...v4.3.0) (2018-08-23)
 
diff --git a/include/bitsery/ext/utils/polymorphism_utils.h b/include/bitsery/ext/utils/polymorphism_utils.h
index 8ed8c96..79132dc 100644
--- a/include/bitsery/ext/utils/polymorphism_utils.h
+++ b/include/bitsery/ext/utils/polymorphism_utils.h
@@ -44,14 +44,10 @@ namespace bitsery {
 // although you can add all derivates to same base like this:
 // template <> PolymorphicBaseClass<Animal>:PolymorphicDerivedClasses<Dog, Cat, Bulldog, GoldenRetriever>{};
 // it will not work when you try to serialize Dog*, because it will not find Bulldog and GoldenRetriever
-        namespace {
-            // this class must be in anonymous namespace, so that it would generate different symbols when defining different hierarchies in different translation units
-            // https://github.com/fraillt/bitsery/issues/9
-            template<typename TBase>
-            struct PolymorphicBaseClass {
-                using Childs = PolymorphicClassesList<>;
-            };
-        }
+        template<typename TBase>
+        struct PolymorphicBaseClass {
+            using Childs = PolymorphicClassesList<>;
+        };
 
 //derive from this class when specifying childs for your base class, atleast one child must exists, hence T1
 //e.g.
@@ -74,11 +70,11 @@ namespace bitsery {
 
             void *create() const final {
                 return toBase(new TDerived{});
-            };
+            }
 
             void process(void *ser, void *obj) const final {
                 static_cast<TSerializer *>(ser)->object(*static_cast<TDerived *>(fromBase(obj)));
-            };
+            }
 
         private:
 
@@ -188,7 +184,7 @@ namespace bitsery {
                 static_assert(std::is_base_of<TBase, TDerived>::value, "TDerived must be derived from TBase");
                 static_assert(!std::is_abstract<TDerived>::value, "TDerived cannot be abstract");
                 addToMap<TSerializer, TBase, TDerived>(std::false_type{});
-            };
+            }
 
 
             template<typename Serializer, typename Writer, typename TBase>