bpo-33767: Fix improper use of SystemError by mmap.mmap objects (GH-7381)

Raise TypeError instead of SystemError for unsupported operations.

Lib/test/test_mmap.py

@@ -734,6 +734,13 @@ class MmapTests(unittest.TestCase):
         self.assertRaises(ValueError, m.write_byte, 42)
         self.assertRaises(ValueError, m.write, b'abc')
 
+    def test_concat_repeat_exception(self):
+        m = mmap.mmap(-1, 16)
+        with self.assertRaises(TypeError):
+            m + m
+        with self.assertRaises(TypeError):
+            m * 2
+
 
 class LargeMmapTests(unittest.TestCase):
 

Misc/NEWS.d/next/Library/2018-06-03-22-41-59.bpo-33767.2e82g3.rst

+The concatenation (``+``) and repetition (``*``) sequence operations now
+raise :exc:`TypeError` instead of :exc:`SystemError` when performed on
+:class:`mmap.mmap` objects.  Patch by Zackery Spytz.

Modules/mmapmodule.c

@@ -812,24 +812,6 @@ mmap_subscript(mmap_object *self, PyObject *item)
     }
 }
 
-static PyObject *
-mmap_concat(mmap_object *self, PyObject *bb)
-{
-    CHECK_VALID(NULL);
-    PyErr_SetString(PyExc_SystemError,
-                    "mmaps don't support concatenation");
-    return NULL;
-}
-
-static PyObject *
-mmap_repeat(mmap_object *self, Py_ssize_t n)
-{
-    CHECK_VALID(NULL);
-    PyErr_SetString(PyExc_SystemError,
-                    "mmaps don't support repeat operation");
-    return NULL;
-}
-
 static int
 mmap_ass_item(mmap_object *self, Py_ssize_t i, PyObject *v)
 {
@@ -949,8 +931,8 @@ mmap_ass_subscript(mmap_object *self, PyObject *item, PyObject *value)
 
 static PySequenceMethods mmap_as_sequence = {
     (lenfunc)mmap_length,            /*sq_length*/
-    (binaryfunc)mmap_concat,         /*sq_concat*/
-    (ssizeargfunc)mmap_repeat,       /*sq_repeat*/
+    0,                               /*sq_concat*/
+    0,                               /*sq_repeat*/
     (ssizeargfunc)mmap_item,         /*sq_item*/
     0,                               /*sq_slice*/
     (ssizeobjargproc)mmap_ass_item,  /*sq_ass_item*/