diff -r 135e1a8144ec Include/abstract.h
--- a/Include/abstract.h	Mon Jan 09 11:21:37 2017 +0100
+++ b/Include/abstract.h	Tue Jan 10 12:51:00 2017 +0100
@@ -187,17 +187,6 @@ PyAPI_FUNC(PyObject **) _PyStack_UnpackD
     PyObject **kwnames,
     PyObject *func);

-/* Suggested size (number of positional arguments) for arrays of PyObject*
-   allocated on a C stack to avoid allocating memory on the heap memory. Such
-   array is used to pass positional arguments to call functions of the
-   _PyObject_FastCall() family.
-
-   The size is chosen to not abuse the C stack and so limit the risk of stack
-   overflow. The size is also chosen to allow using the small stack for most
-   function calls of the Python standard library. On 64-bit CPU, it allocates
-   40 bytes on the stack. */
-#define _PY_FASTCALL_SMALL_STACK 5
-
 /* Call the callable object 'callable' with the "fast call" calling convention:
    args is a C array for positional arguments (nargs is the number of
    positional arguments), kwargs is a dictionary for keyword arguments.
diff -r 135e1a8144ec Objects/abstract.c
--- a/Objects/abstract.c	Mon Jan 09 11:21:37 2017 +0100
+++ b/Objects/abstract.c	Tue Jan 10 12:51:00 2017 +0100
@@ -2337,7 +2337,6 @@ PyObject *
 _PyObject_Call_Prepend(PyObject *callable,
                        PyObject *obj, PyObject *args, PyObject *kwargs)
 {
-    PyObject *small_stack[_PY_FASTCALL_SMALL_STACK];
     PyObject **stack;
     Py_ssize_t argcount;
     PyObject *result;
@@ -2345,29 +2344,22 @@ PyObject *
     assert(PyTuple_Check(args));

     argcount = PyTuple_GET_SIZE(args);
-    if (argcount + 1 <= (Py_ssize_t)Py_ARRAY_LENGTH(small_stack)) {
-        stack = small_stack;
-    }
-    else {
-        stack = PyMem_Malloc((argcount + 1) * sizeof(PyObject *));
-        if (stack == NULL) {
-            PyErr_NoMemory();
-            return NULL;
-        }
+    stack = PyMem_Malloc((argcount + 1) * sizeof(PyObject *));
+    if (stack == NULL) {
+        PyErr_NoMemory();
+        return NULL;
     }

     /* use borrowed references */
     stack[0] = obj;
     memcpy(&stack[1],
-              &PyTuple_GET_ITEM(args, 0),
-              argcount * sizeof(PyObject *));
+           &PyTuple_GET_ITEM(args, 0),
+           argcount * sizeof(PyObject *));

     result = _PyObject_FastCallDict(callable,
                                     stack, argcount + 1,
                                     kwargs);
-    if (stack != small_stack) {
-        PyMem_Free(stack);
-    }
+    PyMem_Free(stack);
     return result;
 }

@@ -2522,8 +2514,6 @@ static PyObject *
 _PyObject_CallFunctionVa(PyObject *callable, const char *format,
                          va_list va, int is_size_t)
 {
-    PyObject* small_stack[_PY_FASTCALL_SMALL_STACK];
-    const Py_ssize_t small_stack_len = Py_ARRAY_LENGTH(small_stack);
     PyObject **stack;
     Py_ssize_t nargs, i;
     PyObject *result;
@@ -2537,10 +2527,10 @@ static PyObject *
     }

     if (is_size_t) {
-        stack = _Py_VaBuildStack(small_stack, small_stack_len, format, va, &nargs);
+        stack = _Py_VaBuildStack(NULL, 0, format, va, &nargs);
     }
     else {
-        stack = _Py_VaBuildStack_SizeT(small_stack, small_stack_len, format, va, &nargs);
+        stack = _Py_VaBuildStack_SizeT(NULL, 0, format, va, &nargs);
     }
     if (stack == NULL) {
         return NULL;
@@ -2563,9 +2553,6 @@ static PyObject *
     for (i = 0; i < nargs; ++i) {
         Py_DECREF(stack[i]);
     }
-    if (stack != small_stack) {
-        PyMem_Free(stack);
-    }
     return result;
 }

@@ -2703,7 +2690,6 @@ PyObject *
 PyObject *
 _PyObject_VaCallFunctionObjArgs(PyObject *callable, va_list vargs)
 {
-    PyObject *small_stack[_PY_FASTCALL_SMALL_STACK];
     PyObject **stack;
     Py_ssize_t nargs;
     PyObject *result;
@@ -2727,15 +2713,10 @@ PyObject *
     va_end(countva);

     /* Copy arguments */
-    if (nargs <= (Py_ssize_t)Py_ARRAY_LENGTH(small_stack)) {
-        stack = small_stack;
-    }
-    else {
-        stack = PyMem_Malloc(nargs * sizeof(stack[0]));
-        if (stack == NULL) {
-            PyErr_NoMemory();
-            return NULL;
-        }
+    stack = PyMem_Malloc(nargs * sizeof(stack[0]));
+    if (stack == NULL) {
+        PyErr_NoMemory();
+        return NULL;
     }

     for (i = 0; i < nargs; ++i) {
@@ -2744,10 +2725,7 @@ PyObject *

     /* Call the function */
     result = _PyObject_FastCall(callable, stack, nargs);
-
-    if (stack != small_stack) {
-        PyMem_Free(stack);
-    }
+    PyMem_Free(stack);
     return result;
 }

diff -r 135e1a8144ec Python/bltinmodule.c
--- a/Python/bltinmodule.c	Mon Jan 09 11:21:37 2017 +0100
+++ b/Python/bltinmodule.c	Tue Jan 10 12:51:00 2017 +0100
@@ -1186,21 +1186,15 @@ map_traverse(mapobject *lz, visitproc vi
 static PyObject *
 map_next(mapobject *lz)
 {
-    PyObject *small_stack[_PY_FASTCALL_SMALL_STACK];
     PyObject **stack;
     Py_ssize_t niters, nargs, i;
     PyObject *result = NULL;

     niters = PyTuple_GET_SIZE(lz->iters);
-    if (niters <= (Py_ssize_t)Py_ARRAY_LENGTH(small_stack)) {
-        stack = small_stack;
-    }
-    else {
-        stack = PyMem_Malloc(niters * sizeof(stack[0]));
-        if (stack == NULL) {
-            PyErr_NoMemory();
-            return NULL;
-        }
+    stack = PyMem_Malloc(niters * sizeof(stack[0]));
+    if (stack == NULL) {
+        PyErr_NoMemory();
+        return NULL;
     }

     nargs = 0;
@@ -1220,9 +1214,7 @@ exit:
     for (i=0; i < nargs; i++) {
         Py_DECREF(stack[i]);
     }
-    if (stack != small_stack) {
-        PyMem_Free(stack);
-    }
+    PyMem_Free(stack);
     return result;
 }