[cppyy] Fix type conversion for polymorphic classes (#19374)

Author: Vipul-Cariappa

bindings/pyroot/cppyy/CPyCppyy/src/Converters.cxx

@@ -2192,10 +2192,9 @@ template <bool ISCONST>
 PyObject* CPyCppyy::InstancePtrConverter<ISCONST>::FromMemory(void* address)
 {
 // construct python object from C++ instance read at <address>
-    Cppyy::TCppScope_t actual_class = Cppyy::GetActualClass(fClass, *(void**)address);
     if (ISCONST)
-        return BindCppObject(*(void**)address, actual_class);                   // by pointer value
-    return BindCppObject(address, actual_class, CPPInstance::kIsReference);     // modifiable
+        return BindCppObject(*(void**)address, fClass);                   // by pointer value
+    return BindCppObject(address, fClass, CPPInstance::kIsReference);     // modifiable
 }
 
 //----------------------------------------------------------------------------

bindings/pyroot/cppyy/CPyCppyy/src/ProxyWrappers.cxx

@@ -927,19 +927,24 @@ PyObject* CPyCppyy::BindCppObject(Cppyy::TCppObject_t address,
 // successful, no down-casting is attempted?
 // TODO: optimize for final classes
     unsigned new_flags = flags;
-    if (!isRef && (gPinnedTypes.empty() || gPinnedTypes.find(klass) == gPinnedTypes.end())) {
-        Cppyy::TCppType_t clActual = Cppyy::GetActualClass(klass, address);
-
-        if (clActual) {
-            if (clActual != klass) {
-                intptr_t offset = Cppyy::GetBaseOffset(
-                    clActual, klass, address, -1 /* down-cast */, true /* report errors */);
-                if (offset != -1) {   // may fail if clActual not fully defined
-                    address = (void*)((intptr_t)address + offset);
-                    klass = clActual;
+    if (gPinnedTypes.empty() || gPinnedTypes.find(klass) == gPinnedTypes.end()) {
+        if (!isRef) {
+            Cppyy::TCppType_t clActual = Cppyy::GetActualClass(klass, address);
+
+            if (clActual) {
+                if (clActual != klass) {
+                    intptr_t offset = Cppyy::GetBaseOffset(
+                        clActual, klass, address, -1 /* down-cast */, true /* report errors */);
+                    if (offset != -1) {   // may fail if clActual not fully defined
+                        address = (void*)((intptr_t)address + offset);
+                        klass = clActual;
+                    }
                 }
+                new_flags |= CPPInstance::kIsActual;
             }
-            new_flags |= CPPInstance::kIsActual;
+        } else {
+            Cppyy::TCppType_t clActual = Cppyy::GetActualClass(klass, *(void**)address);
+            klass = clActual;
         }
     }
 

bindings/pyroot/cppyy/cppyy/test/test_datatypes.py

@@ -2410,6 +2410,41 @@ def test51_polymorphic_types_in_maps(self):
             else:
                 assert type(v) == gbl.PolymorphicMaps.Derived
 
+    def test52_virtual_inheritance(self):
+        import cppyy
+        from cppyy import gbl
+
+        cppyy.cppdef("""
+        class JetTag {
+        public:
+            JetTag() {}
+            virtual ~JetTag() = default;
+            int jt = 0;
+            std::string name = "NAME";
+        };
+        class BaseTag: public JetTag {
+        public:
+            int bt = 1;
+        } bt;
+        class JetFitTag: public virtual BaseTag {
+        public:
+            int jft = 2;
+        } jft;
+        class JetFit: public virtual JetFitTag {
+        public:
+            int jf = 3;
+        } jf;
+        std::vector<const JetTag*> make() {
+            std::vector<const JetTag*> res;
+            res.push_back(&bt);
+            res.push_back(&jft);
+            res.push_back(&jf);
+            return res;
+        }
+        """)
+
+        for i in gbl.make():
+            assert i.name == "NAME"
 
 if __name__ == "__main__":
     exit(pytest.main(args=['-sv', '-ra', __file__]))