bpo-33738: Fix macros which contradict PEP 384 (GH-7477)

During development of the limited API support for PySide,
we saw an error in a macro that accessed a type field.

This patch fixes the 7 errors in the Python headers.
Macros which were not written as capitals were implemented
as function.

To do the necessary analysis again, a script was included that
parses all headers and looks for "->tp_" in serctions which can
be reached with active limited API.

It is easily possible to call this script as a test.

Error listing:

../../Include/objimpl.h:243
#define PyObject_IS_GC(o) (PyType_IS_GC(Py_TYPE(o)) && \
    (Py_TYPE(o)->tp_is_gc == NULL || Py_TYPE(o)->tp_is_gc(o)))
Action: commented only

../../Include/objimpl.h:362
#define PyType_SUPPORTS_WEAKREFS(t) ((t)->tp_weaklistoffset > 0)
Action: commented only

../../Include/objimpl.h:364
#define PyObject_GET_WEAKREFS_LISTPTR(o) \
    ((PyObject **) (((char *) (o)) + Py_TYPE(o)->tp_weaklistoffset))
Action: commented only

../../Include/pyerrors.h:143
#define PyExceptionClass_Name(x) \
     ((char *)(((PyTypeObject*)(x))->tp_name))
Action: implemented function

../../Include/abstract.h:593
#define PyIter_Check(obj) \
    ((obj)->ob_type->tp_iternext != NULL && \
     (obj)->ob_type->tp_iternext != &_PyObject_NextNotImplemented)
Action: implemented function

../../Include/abstract.h:713
#define PyIndex_Check(obj)                              \
    ((obj)->ob_type->tp_as_number != NULL &&            \
     (obj)->ob_type->tp_as_number->nb_index != NULL)
Action: implemented function

../../Include/abstract.h:924
#define PySequence_ITEM(o, i)\
    ( Py_TYPE(o)->tp_as_sequence->sq_item(o, i) )
Action: commented only

1 files changed, 4 insertions, 0 deletions

diff --git a/Include/objimpl.h b/Include/objimpl.h
index 057bb50cbda..a38906c7dc8 100644
--- a/Include/objimpl.h
+++ b/Include/objimpl.h
@@ -240,8 +240,10 @@ PyAPI_FUNC(Py_ssize_t) _PyGC_CollectIfEnabled(void);
 #define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)
 
 /* Test if an object has a GC head */
+#ifndef Py_LIMITED_API
 #define PyObject_IS_GC(o) (PyType_IS_GC(Py_TYPE(o)) && \
     (Py_TYPE(o)->tp_is_gc == NULL || Py_TYPE(o)->tp_is_gc(o)))
+#endif
 
 PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
 #define PyObject_GC_Resize(type, op, n) \
@@ -359,10 +361,12 @@ PyAPI_FUNC(void) PyObject_GC_Del(void *);
 
 
 /* Test if a type supports weak references */
+#ifndef Py_LIMITED_API
 #define PyType_SUPPORTS_WEAKREFS(t) ((t)->tp_weaklistoffset > 0)
 
 #define PyObject_GET_WEAKREFS_LISTPTR(o) \
     ((PyObject **) (((char *) (o)) + Py_TYPE(o)->tp_weaklistoffset))
+#endif
 
 #ifdef __cplusplus
 }