bpo-33012: Fix invalid function cast warnings with gcc 8 for METH_NOARGS. (GH-6030)

METH_NOARGS functions need only a single argument but they are cast
into a PyCFunction, which takes two arguments.  This triggers an
invalid function cast warning in gcc8 due to the argument mismatch.
Fix this by adding a dummy unused argument.

Author: siddhesh

Doc/extending/newtypes_tutorial.rst

@@ -457,7 +457,7 @@ We define a single method, :meth:`Custom.name()`, that outputs the objects name
 concatenation of the first and last names. ::
 
    static PyObject *
-   Custom_name(CustomObject *self)
+   Custom_name(CustomObject *self, PyObject *Py_UNUSED(ignored))
    {
        if (self->first == NULL) {
            PyErr_SetString(PyExc_AttributeError, "first");

Misc/NEWS.d/next/Build/2018-03-08-20-25-29.bpo-33012.k9Fe1q.rst

@@ -0,0 +1,5 @@
+gcc 8 has added a new warning heuristic to detect invalid function casts and
+a stock python build seems to hit that warning quite often.  The most common
+is the cast of a METH_NOARGS function (that uses just one argument) to a
+PyCFunction. Fix this by adding a dummy argument to all functions that
+implement METH_NOARGS.

Modules/_collectionsmodule.c

@@ -512,7 +512,7 @@ deque_inplace_concat(dequeobject *deque, PyObject *other)
 }
 
 static PyObject *
-deque_copy(PyObject *deque)
+deque_copy(PyObject *deque, PyObject *Py_UNUSED(ignored))
 {
     dequeobject *old_deque = (dequeobject *)deque;
     if (Py_TYPE(deque) == &deque_type) {
@@ -563,7 +563,7 @@ deque_concat(dequeobject *deque, PyObject *other)
         return NULL;
     }
 
-    new_deque = deque_copy((PyObject *)deque);
+    new_deque = deque_copy((PyObject *)deque, NULL);
     if (new_deque == NULL)
         return NULL;
     result = deque_extend((dequeobject *)new_deque, other);
@@ -659,7 +659,7 @@ deque_clear(dequeobject *deque)
 }
 
 static PyObject *
-deque_clearmethod(dequeobject *deque)
+deque_clearmethod(dequeobject *deque, PyObject *Py_UNUSED(ignored))
 {
     deque_clear(deque);
     Py_RETURN_NONE;
@@ -754,7 +754,7 @@ deque_repeat(dequeobject *deque, Py_ssize_t n)
     dequeobject *new_deque;
     PyObject *rv;
 
-    new_deque = (dequeobject *)deque_copy((PyObject *) deque);
+    new_deque = (dequeobject *)deque_copy((PyObject *) deque, NULL);
     if (new_deque == NULL)
         return NULL;
     rv = deque_inplace_repeat(new_deque, n);
@@ -1576,7 +1576,7 @@ static PyNumberMethods deque_as_number = {
  };
 
 static PyObject *deque_iter(dequeobject *deque);
-static PyObject *deque_reviter(dequeobject *deque);
+static PyObject *deque_reviter(dequeobject *deque, PyObject *Py_UNUSED(ignored));
 PyDoc_STRVAR(reversed_doc,
     "D.__reversed__() -- return a reverse iterator over the deque");
 
@@ -1587,9 +1587,9 @@ static PyMethodDef deque_methods[] = {
         METH_O,                  appendleft_doc},
     {"clear",                   (PyCFunction)deque_clearmethod,
         METH_NOARGS,             clear_doc},
-    {"__copy__",                (PyCFunction)deque_copy,
+    {"__copy__",                deque_copy,
         METH_NOARGS,             copy_doc},
-    {"copy",                    (PyCFunction)deque_copy,
+    {"copy",                    deque_copy,
         METH_NOARGS,             copy_doc},
     {"count",                   (PyCFunction)deque_count,
         METH_O,                  count_doc},
@@ -1774,15 +1774,15 @@ dequeiter_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 }
 
 static PyObject *
-dequeiter_len(dequeiterobject *it)
+dequeiter_len(dequeiterobject *it, PyObject *Py_UNUSED(ignored))
 {
     return PyLong_FromSsize_t(it->counter);
 }
 
 PyDoc_STRVAR(length_hint_doc, "Private method returning an estimate of len(list(it)).");
 
 static PyObject *
-dequeiter_reduce(dequeiterobject *it)
+dequeiter_reduce(dequeiterobject *it, PyObject *Py_UNUSED(ignored))
 {
     return Py_BuildValue("O(On)", Py_TYPE(it), it->deque, Py_SIZE(it->deque) - it->counter);
 }
@@ -1841,7 +1841,7 @@ static PyTypeObject dequeiter_type = {
 static PyTypeObject dequereviter_type;
 
 static PyObject *
-deque_reviter(dequeobject *deque)
+deque_reviter(dequeobject *deque, PyObject *Py_UNUSED(ignored))
 {
     dequeiterobject *it;
 
@@ -1896,7 +1896,7 @@ dequereviter_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         return NULL;
     assert(type == &dequereviter_type);
 
-    it = (dequeiterobject*)deque_reviter((dequeobject *)deque);
+    it = (dequeiterobject*)deque_reviter((dequeobject *)deque, NULL);
     if (!it)
         return NULL;
     /* consume items from the queue */
@@ -2001,7 +2001,7 @@ defdict_missing(defdictobject *dd, PyObject *key)
 PyDoc_STRVAR(defdict_copy_doc, "D.copy() -> a shallow copy of D.");
 
 static PyObject *
-defdict_copy(defdictobject *dd)
+defdict_copy(defdictobject *dd, PyObject *Py_UNUSED(ignored))
 {
     /* This calls the object's class.  That only works for subclasses
        whose class constructor has the same signature.  Subclasses that
@@ -2015,7 +2015,7 @@ defdict_copy(defdictobject *dd)
 }
 
 static PyObject *
-defdict_reduce(defdictobject *dd)
+defdict_reduce(defdictobject *dd, PyObject *Py_UNUSED(ignored))
 {
     /* __reduce__ must return a 5-tuple as follows:
 

Modules/_datetimemodule.c

@@ -2590,7 +2590,7 @@ delta_getstate(PyDateTime_Delta *self)
 }
 
 static PyObject *
-delta_total_seconds(PyObject *self)
+delta_total_seconds(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
     PyObject *total_seconds;
     PyObject *total_microseconds;
@@ -2606,7 +2606,7 @@ delta_total_seconds(PyObject *self)
 }
 
 static PyObject *
-delta_reduce(PyDateTime_Delta* self)
+delta_reduce(PyDateTime_Delta* self, PyObject *Py_UNUSED(ignored))
 {
     return Py_BuildValue("ON", Py_TYPE(self), delta_getstate(self));
 }
@@ -2627,7 +2627,7 @@ static PyMemberDef delta_members[] = {
 };
 
 static PyMethodDef delta_methods[] = {
-    {"total_seconds", (PyCFunction)delta_total_seconds, METH_NOARGS,
+    {"total_seconds", delta_total_seconds, METH_NOARGS,
      PyDoc_STR("Total seconds in the duration.")},
 
     {"__reduce__", (PyCFunction)delta_reduce, METH_NOARGS,
@@ -2991,7 +2991,7 @@ date_repr(PyDateTime_Date *self)
 }
 
 static PyObject *
-date_isoformat(PyDateTime_Date *self)
+date_isoformat(PyDateTime_Date *self, PyObject *Py_UNUSED(ignored))
 {
     return PyUnicode_FromFormat("%04d-%02d-%02d",
                                 GET_YEAR(self), GET_MONTH(self), GET_DAY(self));
@@ -3006,7 +3006,7 @@ date_str(PyDateTime_Date *self)
 
 
 static PyObject *
-date_ctime(PyDateTime_Date *self)
+date_ctime(PyDateTime_Date *self, PyObject *Py_UNUSED(ignored))
 {
     return format_ctime(self, 0, 0, 0);
 }
@@ -3055,15 +3055,15 @@ date_format(PyDateTime_Date *self, PyObject *args)
 /* ISO methods. */
 
 static PyObject *
-date_isoweekday(PyDateTime_Date *self)
+date_isoweekday(PyDateTime_Date *self, PyObject *Py_UNUSED(ignored))
 {
     int dow = weekday(GET_YEAR(self), GET_MONTH(self), GET_DAY(self));
 
     return PyLong_FromLong(dow + 1);
 }
 
 static PyObject *
-date_isocalendar(PyDateTime_Date *self)
+date_isocalendar(PyDateTime_Date *self, PyObject *Py_UNUSED(ignored))
 {
     int  year         = GET_YEAR(self);
     int  week1_monday = iso_week1_monday(year);
@@ -3100,7 +3100,7 @@ date_richcompare(PyObject *self, PyObject *other, int op)
 }
 
 static PyObject *
-date_timetuple(PyDateTime_Date *self)
+date_timetuple(PyDateTime_Date *self, PyObject *Py_UNUSED(ignored))
 {
     return build_struct_time(GET_YEAR(self),
                              GET_MONTH(self),
@@ -3149,14 +3149,14 @@ date_hash(PyDateTime_Date *self)
 }
 
 static PyObject *
-date_toordinal(PyDateTime_Date *self)
+date_toordinal(PyDateTime_Date *self, PyObject *Py_UNUSED(ignored))
 {
     return PyLong_FromLong(ymd_to_ord(GET_YEAR(self), GET_MONTH(self),
                                      GET_DAY(self)));
 }
 
 static PyObject *
-date_weekday(PyDateTime_Date *self)
+date_weekday(PyDateTime_Date *self, PyObject *Py_UNUSED(ignored))
 {
     int dow = weekday(GET_YEAR(self), GET_MONTH(self), GET_DAY(self));
 
@@ -3435,7 +3435,7 @@ tzinfo_fromutc(PyDateTime_TZInfo *self, PyObject *dt)
  */
 
 static PyObject *
-tzinfo_reduce(PyObject *self)
+tzinfo_reduce(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
     PyObject *args, *state;
     PyObject *getinitargs, *getstate;
@@ -3502,7 +3502,7 @@ static PyMethodDef tzinfo_methods[] = {
     {"fromutc",         (PyCFunction)tzinfo_fromutc,            METH_O,
      PyDoc_STR("datetime in UTC -> datetime in local time.")},
 
-    {"__reduce__",  (PyCFunction)tzinfo_reduce,             METH_NOARGS,
+    {"__reduce__",  tzinfo_reduce,             METH_NOARGS,
      PyDoc_STR("-> (cls, state)")},
 
     {NULL, NULL}
@@ -3720,7 +3720,7 @@ timezone_fromutc(PyDateTime_TimeZone *self, PyDateTime_DateTime *dt)
 }
 
 static PyObject *
-timezone_getinitargs(PyDateTime_TimeZone *self)
+timezone_getinitargs(PyDateTime_TimeZone *self, PyObject *Py_UNUSED(ignored))
 {
     if (self->name == NULL)
         return Py_BuildValue("(O)", self->offset);
@@ -5173,7 +5173,7 @@ datetime_isoformat(PyDateTime_DateTime *self, PyObject *args, PyObject *kw)
 }
 
 static PyObject *
-datetime_ctime(PyDateTime_DateTime *self)
+datetime_ctime(PyDateTime_DateTime *self, PyObject *Py_UNUSED(ignored))
 {
     return format_ctime((PyDateTime_Date *)self,
                         DATE_GET_HOUR(self),
@@ -5652,7 +5652,7 @@ datetime_astimezone(PyDateTime_DateTime *self, PyObject *args, PyObject *kw)
 }
 
 static PyObject *
-datetime_timetuple(PyDateTime_DateTime *self)
+datetime_timetuple(PyDateTime_DateTime *self, PyObject *Py_UNUSED(ignored))
 {
     int dstflag = -1;
 
@@ -5727,7 +5727,7 @@ local_to_seconds(int year, int month, int day,
 #define EPOCH_SECONDS (719163LL * 24 * 60 * 60)
 
 static PyObject *
-datetime_timestamp(PyDateTime_DateTime *self)
+datetime_timestamp(PyDateTime_DateTime *self, PyObject *Py_UNUSED(ignored))
 {
     PyObject *result;
 
@@ -5736,7 +5736,7 @@ datetime_timestamp(PyDateTime_DateTime *self)
         delta = datetime_subtract((PyObject *)self, PyDateTime_Epoch);
         if (delta == NULL)
             return NULL;
-        result = delta_total_seconds(delta);
+        result = delta_total_seconds(delta, NULL);
         Py_DECREF(delta);
     }
     else {
@@ -5757,15 +5757,15 @@ datetime_timestamp(PyDateTime_DateTime *self)
 }
 
 static PyObject *
-datetime_getdate(PyDateTime_DateTime *self)
+datetime_getdate(PyDateTime_DateTime *self, PyObject *Py_UNUSED(ignored))
 {
     return new_date(GET_YEAR(self),
                     GET_MONTH(self),
                     GET_DAY(self));
 }
 
 static PyObject *
-datetime_gettime(PyDateTime_DateTime *self)
+datetime_gettime(PyDateTime_DateTime *self, PyObject *Py_UNUSED(ignored))
 {
     return new_time(DATE_GET_HOUR(self),
                     DATE_GET_MINUTE(self),
@@ -5776,7 +5776,7 @@ datetime_gettime(PyDateTime_DateTime *self)
 }
 
 static PyObject *
-datetime_gettimetz(PyDateTime_DateTime *self)
+datetime_gettimetz(PyDateTime_DateTime *self, PyObject *Py_UNUSED(ignored))
 {
     return new_time(DATE_GET_HOUR(self),
                     DATE_GET_MINUTE(self),
@@ -5787,7 +5787,7 @@ datetime_gettimetz(PyDateTime_DateTime *self)
 }
 
 static PyObject *
-datetime_utctimetuple(PyDateTime_DateTime *self)
+datetime_utctimetuple(PyDateTime_DateTime *self, PyObject *Py_UNUSED(ignored))
 {
     int y, m, d, hh, mm, ss;
     PyObject *tzinfo;

Modules/_io/bytesio.c

@@ -758,7 +758,7 @@ _io_BytesIO_close_impl(bytesio *self)
  */
 
 static PyObject *
-bytesio_getstate(bytesio *self)
+bytesio_getstate(bytesio *self, PyObject *Py_UNUSED(ignored))
 {
     PyObject *initvalue = _io_BytesIO_getvalue_impl(self);
     PyObject *dict;

Modules/_io/fileio.c

@@ -1123,7 +1123,7 @@ _io_FileIO_isatty_impl(fileio *self)
 }
 
 static PyObject *
-fileio_getstate(fileio *self)
+fileio_getstate(fileio *self, PyObject *Py_UNUSED(ignored))
 {
     PyErr_Format(PyExc_TypeError,
                  "cannot serialize '%s' object", Py_TYPE(self)->tp_name);

Modules/_io/stringio.c

@@ -812,7 +812,7 @@ _io_StringIO_seekable_impl(stringio *self)
 */
 
 static PyObject *
-stringio_getstate(stringio *self)
+stringio_getstate(stringio *self, PyObject *Py_UNUSED(ignored))
 {
     PyObject *initvalue = _io_StringIO_getvalue_impl(self);
     PyObject *dict;

Modules/_io/textio.c

@@ -66,7 +66,7 @@ PyDoc_STRVAR(textiobase_detach_doc,
     );
 
 static PyObject *
-textiobase_detach(PyObject *self)
+textiobase_detach(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
     return _unsupported("detach");
 }
@@ -148,7 +148,7 @@ textiobase_errors_get(PyObject *self, void *context)
 
 
 static PyMethodDef textiobase_methods[] = {
-    {"detach", (PyCFunction)textiobase_detach, METH_NOARGS, textiobase_detach_doc},
+    {"detach", textiobase_detach, METH_NOARGS, textiobase_detach_doc},
     {"read", textiobase_read, METH_VARARGS, textiobase_read_doc},
     {"readline", textiobase_readline, METH_VARARGS, textiobase_readline_doc},
     {"write", textiobase_write, METH_VARARGS, textiobase_write_doc},

Modules/_io/winconsoleio.c

@@ -1057,7 +1057,7 @@ _io__WindowsConsoleIO_isatty_impl(winconsoleio *self)
 }
 
 static PyObject *
-winconsoleio_getstate(winconsoleio *self)
+winconsoleio_getstate(winconsoleio *self, PyObject *Py_UNUSED(ignored))
 {
     PyErr_Format(PyExc_TypeError,
                  "cannot serialize '%s' object", Py_TYPE(self)->tp_name);