From 782b690ed7ea33556e96f9e19d60846af4507146 Mon Sep 17 00:00:00 2001
From: Ben Frederickson <github@benfrederickson.com>
Date: Mon, 11 Dec 2017 11:05:26 -0800
Subject: [PATCH] Fix Memory Leak in Python Bindings.

The default return_value_policy for py::cast calls is return_value_policy::automatic_reference
(as described here:
http://pybind11.readthedocs.io/en/stable/advanced/functions.html#return-value-policies).

This means that pybind was treating the index as a reference, and not taking ownership of it
and calling the desctructor when the python object was freed. Fix by explicitly telling
pybind to take ownership here.
---
 python_bindings/nmslib.cc | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/python_bindings/nmslib.cc b/python_bindings/nmslib.cc
index e24edfa..8b4c281 100644
--- a/python_bindings/nmslib.cc
+++ b/python_bindings/nmslib.cc
@@ -305,6 +305,7 @@ struct IndexWrapper {
   }
 
   ~IndexWrapper() {
+    LOG(LIB_DEBUG) << "Destroying Index";
     freeObjectVector(&data);
   }
 
@@ -386,17 +387,17 @@ PYBIND11_PLUGIN(nmslib) {
       switch (dtype) {
         case DISTTYPE_FLOAT: {
           auto index = new IndexWrapper<float>(method, space, space_params, data_type, dtype);
-          ret = py::cast(index);
+          ret = py::cast(index, py::return_value_policy::take_ownership);
           break;
         }
         case DISTTYPE_DOUBLE: {
           auto index = new IndexWrapper<double>(method, space, space_params, data_type, dtype);
-          ret = py::cast(index);
+          ret = py::cast(index, py::return_value_policy::take_ownership);
           break;
         }
         case DISTTYPE_INT: {
           auto index = new IndexWrapper<int>(method, space, space_params, data_type, dtype);
-          ret = py::cast(index);
+          ret = py::cast(index, py::return_value_policy::take_ownership);
           break;
         }
         default: