[cpyrt] Cache anonymous-enum constant values in CPPDataMember

src/cpyrt/CPPDataMember.cxx

@@ -88,9 +88,17 @@ static PyObject* dm_get(CPPDataMember* dm, CPPInstance* pyobj,
     }
 
     if (interop::IsEnumConstant(dm->fScope)) {
-      // anonymous enum
-      return pyval_from_enum(interop::ResolveEnum(dm->fScope), nullptr, nullptr,
-                             dm->fScope);
+      // anonymous enum; cache the value in fDescription like the named case
+      // above: once kIsEnumPrep is cleared this block is not reached again
+      PyObject* pyval = pyval_from_enum(interop::ResolveEnum(dm->fScope),
+                                        nullptr, nullptr, dm->fScope);
+      if (pyval) {
+        Py_DECREF(dm->fDescription);
+        dm->fDescription = pyval;
+        dm->fFlags |= kIsEnumType;
+        Py_INCREF(pyval);
+        return pyval;
+      }
     }
   }
   // non-initialized or public data accesses through class (e.g. by help())

test/test_datatypes.py

@@ -2736,3 +2736,21 @@ def test55_qt_cache_alias_collision(self):
         ns.take_schar("e")
         ns.take_int8(101)
         raises(TypeError, ns.take_int8, "e")
+
+
+class TestANONENUM:
+    def test01_anonymous_enum_repeated_access(self):
+        """An anonymous-enum constant keeps its value across accesses"""
+
+        import cppjit
+
+        cppjit.cppdef("""\
+        namespace AnonEnum { struct Holder { enum { kAnon = 42 }; }; }""")
+
+        h = cppjit.gbl.AnonEnum.Holder()
+
+        # the value is computed on the first access and cached; without the
+        # cache later accesses fall through to the data-member converter
+        assert h.kAnon == 42
+        assert h.kAnon == 42
+        assert h.kAnon == 42