SF Patch #661440: Refactor and streamline PyCFunction_Call

Refactor code in PyCFunction_Call giving a modest (tiny) speed boost,
a slight improvement in semantics (now detects invalid flag combinations),
and (arguably) improved clarity (making it blindingly clear which flag
combinations are allowed).  All this comes at a cost of a few lines of
code duplication.

* Folded test for METH_KEYWORDS into the switch/case.
* Deferred testing for an empty dictionary until when and where needed.
* Make a similar deferral for filling the "size" variable.
* Inverted the dictionary test so that the common case falls though
  instead of making a jump.

Objects/methodobject.c

@@ -62,48 +62,58 @@ PyCFunction_Call(PyObject *func, PyObject *arg, PyObject *kw)
 	PyCFunctionObject* f = (PyCFunctionObject*)func;
 	PyCFunction meth = PyCFunction_GET_FUNCTION(func);
 	PyObject *self = PyCFunction_GET_SELF(func);
-	int flags = PyCFunction_GET_FLAGS(func) & ~(METH_CLASS | METH_STATIC);
-	int size = PyTuple_GET_SIZE(arg);
+	int size;
 
-	if (flags & METH_KEYWORDS) {
-		return (*(PyCFunctionWithKeywords)meth)(self, arg, kw);
-	}
-	if (kw != NULL && PyDict_Size(kw) != 0) {
-		PyErr_Format(PyExc_TypeError,
-			     "%.200s() takes no keyword arguments",
-			     f->m_ml->ml_name);
-		return NULL;
-	}
-
-	switch (flags) {
+	switch (PyCFunction_GET_FLAGS(func) & ~(METH_CLASS | METH_STATIC)) {
 	case METH_VARARGS:
+		if (kw == NULL || PyDict_Size(kw) == 0)
 			return (*meth)(self, arg);
+		break;
+	case METH_VARARGS | METH_KEYWORDS:
+		return (*(PyCFunctionWithKeywords)meth)(self, arg, kw);
 	case METH_NOARGS:
+		if (kw == NULL || PyDict_Size(kw) == 0) {
+			size = PyTuple_GET_SIZE(arg);
 			if (size == 0)
 				return (*meth)(self, NULL);
 			PyErr_Format(PyExc_TypeError,
 			    "%.200s() takes no arguments (%d given)",
 			    f->m_ml->ml_name, size);
 			return NULL;
+		}
+		break;
 	case METH_O:
+		if (kw == NULL || PyDict_Size(kw) == 0) {
+			size = PyTuple_GET_SIZE(arg);
 			if (size == 1)
 				return (*meth)(self, PyTuple_GET_ITEM(arg, 0));
 			PyErr_Format(PyExc_TypeError,
 			    "%.200s() takes exactly one argument (%d given)",
 			    f->m_ml->ml_name, size);
 			return NULL;
+		}
+		break;
 	case METH_OLDARGS:
 		/* the really old style */
+		if (kw == NULL || PyDict_Size(kw) == 0) {
+			size = PyTuple_GET_SIZE(arg);
 			if (size == 1)
 				arg = PyTuple_GET_ITEM(arg, 0);
 			else if (size == 0)
 				arg = NULL;
 			return (*meth)(self, arg);
+		}
+		break;
+	case METH_OLDARGS | METH_KEYWORDS:
+		return (*(PyCFunctionWithKeywords)meth)(self, arg, kw);
 	default:
 		/* should never get here ??? */
 		PyErr_BadInternalCall();
 		return NULL;
 	}
+	PyErr_Format(PyExc_TypeError, "%.200s() takes no keyword arguments",
+		     f->m_ml->ml_name);
+	return NULL;
 }
 
 /* Methods (the standard built-in methods, that is) */