diff -r ac0f7ed0e94d Doc/whatsnew/3.6.rst
--- a/Doc/whatsnew/3.6.rst	Tue Dec 01 00:40:50 2015 +0200
+++ b/Doc/whatsnew/3.6.rst	Tue Dec 01 16:47:30 2015 +0200
@@ -195,7 +195,13 @@ Deprecated Python modules, functions and
 Deprecated functions and types of the C API
 -------------------------------------------
 
-* None yet.
+* Deprecated deleting attributes with :c:func:`PyObject_SetAttr` and
+  :c:func:`PyObject_SetAttrString` and deleting items with
+  :c:func:`PySequence_SetItem`.  Use :c:func:`PyObject_DelAttr`,
+  :c:func:`PyObject_DelAttrString` and :c:func:`PySequence_DelItem` instead.
+  ``PyObject_DelAttr()`` and ``PyObject_DelAttrString()`` now are implemented
+  as functions, not macros.
+  (Contributed by Serhiy Storchaka in :issue:`XXXXX`.)
 
 
 Deprecated features
diff -r ac0f7ed0e94d Include/abstract.h
--- a/Include/abstract.h	Tue Dec 01 00:40:50 2015 +0200
+++ b/Include/abstract.h	Tue Dec 01 16:47:30 2015 +0200
@@ -207,7 +207,7 @@ xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 
        */
 
-     /* implemented as a macro:
+     /* Implemented elsewhere:
 
      int PyObject_DelAttrString(PyObject *o, const char *attr_name);
 
@@ -216,9 +216,8 @@ xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
      statement: del o.attr_name.
 
        */
-#define  PyObject_DelAttrString(O,A) PyObject_SetAttrString((O),(A),NULL)
 
-     /* implemented as a macro:
+     /* Implemented elsewhere:
 
      int PyObject_DelAttr(PyObject *o, PyObject *attr_name);
 
@@ -227,7 +226,6 @@ xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
      statement: del o.attr_name.
 
        */
-#define  PyObject_DelAttr(O,A) PyObject_SetAttr((O),(A),NULL)
 
      /* Implemented elsewhere:
 
diff -r ac0f7ed0e94d Include/object.h
--- a/Include/object.h	Tue Dec 01 00:40:50 2015 +0200
+++ b/Include/object.h	Tue Dec 01 16:47:30 2015 +0200
@@ -526,9 +526,11 @@ PyAPI_FUNC(PyObject *) PyObject_RichComp
 PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);
 PyAPI_FUNC(PyObject *) PyObject_GetAttrString(PyObject *, const char *);
 PyAPI_FUNC(int) PyObject_SetAttrString(PyObject *, const char *, PyObject *);
+PyAPI_FUNC(int) PyObject_DelAttrString(PyObject *, const char *);
 PyAPI_FUNC(int) PyObject_HasAttrString(PyObject *, const char *);
 PyAPI_FUNC(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
 PyAPI_FUNC(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
+PyAPI_FUNC(int) PyObject_DelAttr(PyObject *, PyObject *);
 PyAPI_FUNC(int) PyObject_HasAttr(PyObject *, PyObject *);
 PyAPI_FUNC(int) _PyObject_IsAbstract(PyObject *);
 PyAPI_FUNC(PyObject *) _PyObject_GetAttrId(PyObject *, struct _Py_Identifier *);
diff -r ac0f7ed0e94d Misc/NEWS
--- a/Misc/NEWS	Tue Dec 01 00:40:50 2015 +0200
+++ b/Misc/NEWS	Tue Dec 01 16:47:30 2015 +0200
@@ -326,6 +326,15 @@ Library
 - Issue #25319: When threading.Event is reinitialized, the underlying condition
   should use a regular lock rather than a recursive lock.
 
+C API
+-----
+
+- Issue #.....: Deprecated deleting attributes with PyObject_SetAttr() and
+  PyObject_SetAttrString() and deleting items with PySequence_SetItem().
+  Use PyObject_DelAttr(), PyObject_DelAttrString() and PySequence_DelItem()
+  instead.  PyObject_DelAttr and PyObject_DelAttrString now are implemented as
+  functions, not macros.
+
 IDLE
 ----
 
diff -r ac0f7ed0e94d Objects/abstract.c
--- a/Objects/abstract.c	Tue Dec 01 00:40:50 2015 +0200
+++ b/Objects/abstract.c	Tue Dec 01 16:47:30 2015 +0200
@@ -1591,6 +1591,12 @@ PySequence_SetItem(PyObject *s, Py_ssize
         return -1;
     }
 
+    if (o == NULL &&
+        PyErr_WarnEx(PyExc_DeprecationWarning,
+                     "Deleting with PySequence_SetItem) is deprecated.  "
+                     "Use PySequence_DelItem() instead.", 1) < 0)
+            return -1;
+
     m = s->ob_type->tp_as_sequence;
     if (m && m->sq_ass_item) {
         if (i < 0) {
diff -r ac0f7ed0e94d Objects/object.c
--- a/Objects/object.c	Tue Dec 01 00:40:50 2015 +0200
+++ b/Objects/object.c	Tue Dec 01 16:47:30 2015 +0200
@@ -802,8 +802,10 @@ PyObject_HasAttrString(PyObject *v, cons
     return 0;
 }
 
-int
-PyObject_SetAttrString(PyObject *v, const char *name, PyObject *w)
+static int _PyObject_SetDelAttr(PyObject *, PyObject *, PyObject *);
+
+static int
+_PyObject_SetDelAttrString(PyObject *v, const char *name, PyObject *w)
 {
     PyObject *s;
     int res;
@@ -813,12 +815,29 @@ PyObject_SetAttrString(PyObject *v, cons
     s = PyUnicode_InternFromString(name);
     if (s == NULL)
         return -1;
-    res = PyObject_SetAttr(v, s, w);
+    res = _PyObject_SetDelAttr(v, s, w);
     Py_XDECREF(s);
     return res;
 }
 
 int
+PyObject_SetAttrString(PyObject *v, const char *name, PyObject *value)
+{
+    if (value == NULL &&
+        PyErr_WarnEx(PyExc_DeprecationWarning,
+                     "Deleting with PyObject_SetAttrString() is deprecated.  "
+                     "Use PyObject_DelAttrString() instead.", 1) < 0)
+            return -1;
+    return _PyObject_SetDelAttrString(v, name, value);
+}
+
+int
+PyObject_DelAttrString(PyObject *v, const char *name)
+{
+    return _PyObject_SetDelAttrString(v, name, NULL);
+}
+
+int
 _PyObject_IsAbstract(PyObject *obj)
 {
     int res;
@@ -910,8 +929,8 @@ PyObject_HasAttr(PyObject *v, PyObject *
     return 0;
 }
 
-int
-PyObject_SetAttr(PyObject *v, PyObject *name, PyObject *value)
+static int
+_PyObject_SetDelAttr(PyObject *v, PyObject *name, PyObject *value)
 {
     PyTypeObject *tp = Py_TYPE(v);
     int err;
@@ -957,6 +976,23 @@ PyObject_SetAttr(PyObject *v, PyObject *
     return -1;
 }
 
+int
+PyObject_SetAttr(PyObject *v, PyObject *name, PyObject *value)
+{
+    if (value == NULL &&
+        PyErr_WarnEx(PyExc_DeprecationWarning,
+                     "Deleting with PyObject_SetAttr() is deprecated.  "
+                     "Use PyObject_DelAttr() instead.", 1) < 0)
+            return -1;
+    return _PyObject_SetDelAttr(v, name, value);
+}
+
+int
+PyObject_DelAttr(PyObject *v, PyObject *name)
+{
+    return _PyObject_SetDelAttr(v, name, NULL);
+}
+
 /* Helper to get a pointer to an object's __dict__ slot, if any */
 
 PyObject **
diff -r ac0f7ed0e94d Objects/weakrefobject.c
--- a/Objects/weakrefobject.c	Tue Dec 01 00:40:50 2015 +0200
+++ b/Objects/weakrefobject.c	Tue Dec 01 16:47:30 2015 +0200
@@ -477,6 +477,8 @@ proxy_setattr(PyWeakReference *proxy, Py
 {
     if (!proxy_checkref(proxy))
         return -1;
+    if (value == NULL)
+        return PyObject_DelAttr(PyWeakref_GET_OBJECT(proxy), name);
     return PyObject_SetAttr(PyWeakref_GET_OBJECT(proxy), name, value);
 }
 
diff -r ac0f7ed0e94d Python/bltinmodule.c
--- a/Python/bltinmodule.c	Tue Dec 01 00:40:50 2015 +0200
+++ b/Python/bltinmodule.c	Tue Dec 01 16:47:30 2015 +0200
@@ -1352,7 +1352,7 @@ static PyObject *
 builtin_delattr_impl(PyModuleDef *module, PyObject *obj, PyObject *name)
 /*[clinic end generated code: output=ef653e698a0b4187 input=db16685d6b4b9410]*/
 {
-    if (PyObject_SetAttr(obj, name, (PyObject *)NULL) != 0)
+    if (PyObject_DelAttr(obj, name) != 0)
         return NULL;
     Py_INCREF(Py_None);
     return Py_None;
diff -r ac0f7ed0e94d Python/ceval.c
--- a/Python/ceval.c	Tue Dec 01 00:40:50 2015 +0200
+++ b/Python/ceval.c	Tue Dec 01 16:47:30 2015 +0200
@@ -2262,7 +2262,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int
             PyObject *name = GETITEM(names, oparg);
             PyObject *owner = POP();
             int err;
-            err = PyObject_SetAttr(owner, name, (PyObject *)NULL);
+            err = PyObject_DelAttr(owner, name);
             Py_DECREF(owner);
             if (err != 0)
                 goto error;