Fix Shiboken.ObjectType.__new__ for Python 2.7

type(QtWidgets.QWidget).__new__(type(QtWidgets.QWidget), "", (), {})
gave a problem in Python 2.7 after transition to PEP 384.

The reason for the problem is a check in Python 2.7 that tries to find
out if the function used to create a new object is a secure (builtin)
one. Therefore, all new types that are generated by a Python function
are filtered out. Unfortunately, Python 2.7 did that assuming that
only Python classes are heap types.

This is at least no longer true since Python 3 migrated to the new
type API where all new types are heap types.

The internal check was therefore changed to do the test for a builtin
"new" function differently. But not in Python 2.7 .

The workaround was to create the Shiboken.ObjectType as a heap type
and then remove that flag from the type. This seems to have no bad
effects, probably because the types did barely change when doing the
transition. Anyway, I will stay tuned and watch out if this later
creates a problem.

Task-number: PYSIDE-816
Change-Id: Ia596716b0e5dff3f1a7155ab6765186ef0b9d179
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

1 files changed, 13 insertions, 0 deletions

diff --git a/sources/shiboken2/libshiboken/basewrapper.cpp b/sources/shiboken2/libshiboken/basewrapper.cpp
index 8fe4710dd..a008fece8 100644
--- a/sources/shiboken2/libshiboken/basewrapper.cpp
+++ b/sources/shiboken2/libshiboken/basewrapper.cpp
@@ -101,6 +101,15 @@ PyTypeObject *SbkObjectType_TypeF(void)
         SbkObjectType_Type_spec.basicsize =
             PepHeapType_SIZE + sizeof(SbkObjectTypePrivate);
         type = reinterpret_cast<PyTypeObject *>(PyType_FromSpec(&SbkObjectType_Type_spec));
+#if PY_VERSION_HEX < 0x03000000
+        // PYSIDE-816: Python 2.7 has a bad check for Py_TPFLAGS_HEAPTYPE in
+        // typeobject.c func tp_new_wrapper. In Python 3 it was updated after
+        // the transition to the new type API, but not in 2.7 . Fortunately,
+        // the types did not change much when transitioning to heaptypes. We
+        // pretend that this type is a normal type in 2.7 and hope that this
+        // has no bad effect.
+        type->tp_flags &= ~Py_TPFLAGS_HEAPTYPE;
+#endif
     }
     return type;
 }
@@ -290,6 +299,10 @@ void SbkObjectTypeDealloc(PyObject* pyObj)
     SbkObjectTypePrivate *sotp = PepType_SOTP(pyObj);
     PyTypeObject *type = reinterpret_cast<PyTypeObject*>(pyObj);
 
+#if PY_VERSION_HEX < 0x03000000
+    // PYSIDE-816: Restore the heap type flag. Better safe than sorry.
+    type->tp_flags |= Py_TPFLAGS_HEAPTYPE;
+#endif
     PyObject_GC_UnTrack(pyObj);
 #ifndef Py_LIMITED_API
     Py_TRASHCAN_SAFE_BEGIN(pyObj);