fix python GIL issue when passing in a torrent_info object that later gets destroyed from within libtorrent

bindings/python/src/session.cpp

@@ -188,7 +188,16 @@ namespace
     {
         // torrent_info objects are always held by a shared_ptr in the python binding
         if (params.has_key("ti") && params.get("ti") != boost::python::object())
-            p.ti = extract<boost::shared_ptr<torrent_info> >(params["ti"]);
+        {
+           // make a copy here. We don't want to end up holding a python-owned
+           // object inside libtorrent. If the last reference goes out of scope
+           // on the C++ side, it will end up freeing the python object
+           // without holding the GIL and likely crash.
+           // https://mail.python.org/pipermail/cplusplus-sig/2007-June/012130.html
+           p.ti = boost::make_shared<torrent_info>(
+              extract<torrent_info const&>(params["ti"]));
+        }
+
 
         if (params.has_key("info_hash"))
             p.info_hash = sha1_hash(bytes(extract<bytes>(params["info_hash"])).arr);
@@ -420,20 +429,20 @@ namespace
         return ret;
     }
 
-	 cache_status get_cache_info1(lt::session& s, torrent_handle h, int flags)
-	 {
-	 	cache_status ret;
-		s.get_cache_info(&ret, h, flags);
-		return ret;
-	 }
+    cache_status get_cache_info1(lt::session& s, torrent_handle h, int flags)
+    {
+       cache_status ret;
+       s.get_cache_info(&ret, h, flags);
+       return ret;
+    }
 
 #ifndef TORRENT_NO_DEPRECATE
-	 cache_status get_cache_status(lt::session& s)
-	 {
-	 	cache_status ret;
-		s.get_cache_info(&ret);
-		return ret;
-	 }
+    cache_status get_cache_status(lt::session& s)
+    {
+       cache_status ret;
+       s.get_cache_info(&ret);
+       return ret;
+    }
 
     dict get_utp_stats(session_status const& st)
     {

bindings/python/test.py

@@ -73,6 +73,25 @@ class test_alerts(unittest.TestCase):
 		print(st.info_hash)
 		self.assertEqual(st.save_path, os.getcwd())
 
+	def test_pop_alerts(self):
+		ses = lt.session({'alert_mask': lt.alert.category_t.all_categories})
+
+		ses.async_add_torrent({"ti": lt.torrent_info("base.torrent"), "save_path": "."})
+# this will cause an error (because of duplicate torrents) and the
+# torrent_info object created here will be deleted once the alert goes out
+# of scope. When that happens, it will decrement the python object, to allow
+# it to release the object.
+# we're trying to catch the error described in this post, with regards to
+# torrent_info.
+# https://mail.python.org/pipermail/cplusplus-sig/2007-June/012130.html
+		ses.async_add_torrent({"ti": lt.torrent_info("base.torrent"), "save_path": "."})
+		time.sleep(1)
+		for i in range(0, 10):
+			alerts = ses.pop_alerts()
+			for a in alerts:
+				print(a.message())
+			time.sleep(0.1)
+
 class test_bencoder(unittest.TestCase):
 
 	def test_bencode(self):

include/libtorrent/heterogeneous_queue.hpp

@@ -163,9 +163,9 @@ namespace libtorrent {
 		const static int header_size = (sizeof(header_t) + sizeof(uintptr_t)
 			- 1) / sizeof(uintptr_t);
 
-		void grow_capacity(int size)
+		void grow_capacity(int const size)
 		{
-			int amount_to_grow = (std::max)(size + header_size
+			int const amount_to_grow = (std::max)(size + header_size
 				, (std::max)(m_capacity * 3 / 2, 128));
 
 			uintptr_t* new_storage = new uintptr_t[m_capacity + amount_to_grow];