Fix multiple inheritance scenario with managed dict

Author: msimacek

graalpython/com.oracle.graal.python.test/src/tests/cpyext/test_object_dict.py

@@ -45,12 +45,13 @@
 
 NativeTypeWithDict = CPyExtType(
     name='NativeTypeWithDict',
-    cmembers='PyObject* dict;',
+    cmembers='int some_field; PyObject* dict;',
     tp_dictoffset='offsetof(NativeTypeWithDictObject, dict)',
     tp_getset='{"__dict__", PyObject_GenericGetDict, PyObject_GenericSetDict}',
 )
 
 NativeHeapTypeWithoutDict = CPyExtHeapType(
+    cmembers='int some_field;',
     name='NativeTypeWithManagedDict',
 )
 
@@ -75,7 +76,7 @@
 
 
 # TODO it would be great if we could test creating heap types with Py_TPFLAGS_MANAGED_DICT, because pybind11 does that,
-# but there's no way to do that without abusing abusing implementations details
+# but there's no way to do that without abusing implementations details
 
 
 class NativeSubtypeWithDict(NativeTypeWithDict):
@@ -107,3 +108,15 @@ def test_dict(self):
         self.assert_has_working_dict(NativeHeapTypeWithDict())
         self.assert_has_working_dict(NativeSubtypeWithDict())
         self.assert_has_working_dict(NativeSubtypeWithAddedDict())
+
+    def test_multiple_inheritance(self):
+        class Base1(NativeTypeWithoutDict):
+            pass
+
+        class Base2(NativeTypeWithoutDict):
+            pass
+
+        class Derived(Base1, Base2):
+            pass
+
+        self.assert_has_working_dict(Derived())

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/type/TypeNodes.java

@@ -2356,18 +2356,24 @@ private static void addNativeSlots(TypeNewContext ctx, PythonManagedClass python
             long dictOffset = GetDictOffsetNode.executeUncached(base);
             long weakListOffset = GetWeakListOffsetNode.executeUncached(base);
             long itemSize = GetItemSizeNode.executeUncached(base);
-            if (ctx.addDict) {
-                if (itemSize != 0) {
-                    dictOffset = -SIZEOF_PY_OBJECT_PTR;
-                } else {
-                    dictOffset = slotOffset;
-                }
+            if (ctx.addDict && itemSize != 0) {
+                dictOffset = -SIZEOF_PY_OBJECT_PTR;
                 slotOffset += SIZEOF_PY_OBJECT_PTR;
             }
             if (ctx.addWeak) {
                 weakListOffset = slotOffset;
                 slotOffset += SIZEOF_PY_OBJECT_PTR;
             }
+            if (ctx.addDict && itemSize == 0) {
+                long flags = GetTypeFlagsNode.executeUncached(pythonClass) | MANAGED_DICT;
+                SetTypeFlagsNode.executeUncached(pythonClass, flags);
+                /*
+                 * Negative offsets are computed from the end of the structure. Our managed dict is
+                 * right before the start of the object. CPython has 3 fields there, so our formula
+                 * differs.
+                 */
+                dictOffset = -slotOffset - SIZEOF_PY_OBJECT_PTR;
+            }
             SetDictOffsetNode.executeUncached(pythonClass, dictOffset);
             SetBasicSizeNode.executeUncached(pythonClass, slotOffset);
             SetItemSizeNode.executeUncached(pythonClass, itemSize);