[3.7] bpo-37170: Fix the cast on error in PyLong_AsUnsignedLongLongMask() (GH-13860) (GH-13896)

(cherry picked from commit dc2476500d)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

Doc/c-api/long.rst

@@ -259,7 +259,8 @@ distinguished from a number.  Use :c:func:`PyErr_Occurred` to disambiguate.
    If the value of *obj* is out of range for an :c:type:`unsigned long`,
    return the reduction of that value modulo ``ULONG_MAX + 1``.
 
-   Returns ``-1`` on error.  Use :c:func:`PyErr_Occurred` to disambiguate.
+   Returns ``(unsigned long)-1`` on error.  Use :c:func:`PyErr_Occurred` to
+   disambiguate.
 
 
 .. c:function:: unsigned long long PyLong_AsUnsignedLongLongMask(PyObject *obj)
@@ -271,7 +272,8 @@ distinguished from a number.  Use :c:func:`PyErr_Occurred` to disambiguate.
    If the value of *obj* is out of range for an :c:type:`unsigned long long`,
    return the reduction of that value modulo ``PY_ULLONG_MAX + 1``.
 
-   Returns ``-1`` on error.  Use :c:func:`PyErr_Occurred` to disambiguate.
+   Returns ``(unsigned long long)-1`` on error.  Use :c:func:`PyErr_Occurred`
+   to disambiguate.
 
 
 .. c:function:: double PyLong_AsDouble(PyObject *pylong)

Misc/NEWS.d/next/C API/2019-06-06-08-47-04.bpo-37170.hO_fpM.rst

@@ -0,0 +1 @@
+Fix the cast on error in :c:func:`PyLong_AsUnsignedLongLongMask()`.

Modules/_testcapimodule.c

@@ -816,6 +816,26 @@ test_long_as_size_t(PyObject *self)
     return Py_None;
 }
 
+static PyObject *
+test_long_as_unsigned_long_long_mask(PyObject *self,
+                                     PyObject *Py_UNUSED(ignored))
+{
+    unsigned long long res = PyLong_AsUnsignedLongLongMask(NULL);
+
+    if (res != (unsigned long long)-1 || !PyErr_Occurred()) {
+        return raiseTestError("test_long_as_unsigned_long_long_mask",
+                              "PyLong_AsUnsignedLongLongMask(NULL) didn't "
+                              "complain");
+    }
+    if (!PyErr_ExceptionMatches(PyExc_SystemError)) {
+        return raiseTestError("test_long_as_unsigned_long_long_mask",
+                              "PyLong_AsUnsignedLongLongMask(NULL) raised "
+                              "something other than SystemError");
+    }
+    PyErr_Clear();
+    Py_RETURN_NONE;
+}
+
 /* Test the PyLong_AsDouble API. At present this just tests that
    non-integer arguments are handled correctly.
  */
@@ -4663,6 +4683,8 @@ static PyMethodDef TestMethods[] = {
      METH_NOARGS},
     {"test_long_as_double",     (PyCFunction)test_long_as_double,METH_NOARGS},
     {"test_long_as_size_t",     (PyCFunction)test_long_as_size_t,METH_NOARGS},
+    {"test_long_as_unsigned_long_long_mask",
+            (PyCFunction)test_long_as_unsigned_long_long_mask,   METH_NOARGS},
     {"test_long_numbits",       (PyCFunction)test_long_numbits,  METH_NOARGS},
     {"test_k_code",             (PyCFunction)test_k_code,        METH_NOARGS},
     {"test_empty_argparse", (PyCFunction)test_empty_argparse,METH_NOARGS},

Objects/longobject.c

@@ -1309,7 +1309,7 @@ _PyLong_AsUnsignedLongLongMask(PyObject *vv)
 
     if (vv == NULL || !PyLong_Check(vv)) {
         PyErr_BadInternalCall();
-        return (unsigned long) -1;
+        return (unsigned long long) -1;
     }
     v = (PyLongObject *)vv;
     switch(Py_SIZE(v)) {
@@ -1337,7 +1337,7 @@ PyLong_AsUnsignedLongLongMask(PyObject *op)
 
     if (op == NULL) {
         PyErr_BadInternalCall();
-        return (unsigned long)-1;
+        return (unsigned long long)-1;
     }
 
     if (PyLong_Check(op)) {