.

bigfile/_bigfile.c

@@ -986,6 +986,23 @@ pyfile_new(PyTypeObject *type, PyObject *args, PyObject *kw)
             Py_DECREF(blkmmapper);
             return NULL;
         }
+
+        if (blkmmap_ops->loadblk ||
+            blkmmap_ops->storeblk)
+        {
+            Py_DECREF(blkmmapper);
+            return PyErr_Format(PyExc_TypeError,
+                "%s: .blkmmapper: !mmap methods present", type->tp_name);
+        }
+
+        if (!(blkmmap_ops->mmap_setup_read &&
+              blkmmap_ops->remmap_blk_read &&
+              blkmmap_ops->munmap))
+        {
+            Py_DECREF(blkmmapper);
+            return PyErr_Format(PyExc_TypeError,
+                "%s: .blkmmapper: not all mmap methods present", type->tp_name);
+        }
     }
 
     self = (PyBigFile *)PyType_GenericNew(type, args, kw);