Issue #5391: mmap.read_byte() should return unsigned value [0, 255]

instead of signed value [-127, 128].

Lib/test/test_mmap.py

@@ -534,6 +534,15 @@ class MmapTests(unittest.TestCase):
         m.seek(8)
         self.assertRaises(ValueError, m.write, b"bar")
 
+    def test_non_ascii_byte(self):
+        for b in (129, 200, 255): # > 128
+            m = mmap.mmap(-1, 1)
+            m.write_byte(b)
+            self.assertEquals(m[0], b)
+            m.seek(0)
+            self.assertEquals(m.read_byte(), b)
+            m.close()
+
     if os.name == 'nt':
         def test_tagname(self):
             data1 = b"0123456789"

Modules/mmapmodule.c

@@ -204,7 +204,7 @@ mmap_read_byte_method(mmap_object *self,
     if (self->pos < self->size) {
         char value = self->data[self->pos];
         self->pos += 1;
-        return Py_BuildValue("b", value);
+        return Py_BuildValue("B", (unsigned char)value);
     } else {
         PyErr_SetString(PyExc_ValueError, "read byte out of range");
         return NULL;