fix another speical case

bitarray/_bitarray.c

@@ -1881,10 +1881,13 @@ setslice_bitarray(bitarrayobject *self, PyObject *slice,
     /* number of bits by which self has to be increased (decreased) */
     increase = other->nbits - slicelength;
 
-    /* make a copy of other, when the other buffer is part of the self buffer,
-       that is when it's address falls into self's buffer */
-    if (self->ob_item <= other->ob_item &&
-                         other->ob_item <= self->ob_item + Py_SIZE(self)) {
+    /* make a copy of other, when the other buffer is part of the self buffer
+       that is when it's address falls into self's buffer (or vise versa) */
+    if ((self->ob_item <= other->ob_item &&
+                          other->ob_item <= self->ob_item + Py_SIZE(self)) ||
+        (other->ob_item <= self->ob_item &&
+                           self->ob_item <= other->ob_item + Py_SIZE(other)))
+    {
         other = (bitarrayobject *) bitarray_copy(other);
         if (other == NULL)
             return -1;

bitarray/test_bitarray.py

@@ -984,6 +984,20 @@ def test_setslice_self_shared_buffer_2(self):
         c[8:56] = c[55:7:-1]
         self.assertEqual(a, c)
 
+    def test_setslice_self_shared_buffer_3(self):
+        # Requires to check for (in setslice_bitarray()):
+        #
+        #   other->ob_item <= self->ob_item <= other->ob_item + Py_SIZE(other)
+        #
+        a = bitarray('11111111 11000000 00000000')
+        b = bitarray(buffer=memoryview(a)[:2])
+        c = bitarray(buffer=memoryview(a)[1:])
+        self.assertEqual(b, bitarray('11111111 11000000'))
+        self.assertEqual(c, bitarray('11000000 00000000'))
+        c[::-1] = b
+        self.assertEqual(c, bitarray('00000011 11111111'))
+        self.assertEqual(a, bitarray('11111111 00000011 11111111'))
+
     def test_setslice_bitarray(self):
         a = bitarray('11111111 1111')
         a[2:6] = bitarray('0010')