fix crash when loading a resume file where all files have priority 0 (and the torrent finishes before having downloaded anything) and add unit test for this case

src/torrent.cpp

@@ -6766,11 +6766,11 @@ namespace libtorrent
 		if (!m_override_resume_data || m_file_priority.empty())
 		{
 			bdecode_node file_priority = rd.dict_find_list("file_priority");
-			if (file_priority && file_priority.list_size()
+			if (file_priority)
-				<= m_torrent_file->num_files())
 			{
-				int num_files = file_priority.list_size();
+				const int num_files = (std::min)(file_priority.list_size()
-				m_file_priority.resize(num_files);
+					, m_torrent_file->num_files());
+				m_file_priority.resize(num_files, 4);
 				for (int i = 0; i < num_files; ++i)
 				{
 					m_file_priority[i] = file_priority.list_int_value_at(i, 1);
@@ -8262,12 +8262,13 @@ namespace libtorrent
 
 		update_want_peers();
 
-		TORRENT_ASSERT(m_storage);
+		if (m_storage)
-
+		{
-		// we need to keep the object alive during this operation
+			// we need to keep the object alive during this operation
-		inc_refcount("release_files");
+			inc_refcount("release_files");
-		m_ses.disk_thread().async_release_files(m_storage.get()
+			m_ses.disk_thread().async_release_files(m_storage.get()
-			, boost::bind(&torrent::on_cache_flushed, shared_from_this(), _1));
+				, boost::bind(&torrent::on_cache_flushed, shared_from_this(), _1));
+		}
 
 		// this torrent just completed downloads, which means it will fall
 		// under a different limit with the auto-manager. Make sure we
@@ -11172,6 +11173,8 @@ namespace libtorrent
 	{
 //		picker().mark_as_checking(piece);
 
+		TORRENT_ASSERT(m_storage.get());
+
 		inc_refcount("verify_piece");
 		m_ses.disk_thread().async_hash(m_storage.get(), piece, 0
 			, boost::bind(&torrent::on_piece_verified, shared_from_this(), _1)

test/test_resume.cpp

@@ -272,7 +272,45 @@ TORRENT_TEST(file_priorities_seed_mode)
 	TEST_EQUAL(file_priorities[2], 0);
 }
 
-void test_seed_mode(bool file_prio, bool pieces_have, bool piece_prio)
+TORRENT_TEST(zero_file_prio)
+{
+	fprintf(stderr, "test_file_prio\n");
+
+	session ses;
+	boost::shared_ptr<torrent_info> ti = generate_torrent();
+	add_torrent_params p;
+	p.ti = ti;
+	p.save_path = ".";
+
+	entry rd;
+
+	rd["file-format"] = "libtorrent resume file";
+	rd["file-version"] = 1;
+	rd["info-hash"] = ti->info_hash().to_string();
+	rd["blocks per piece"] = (std::max)(1, ti->piece_length() / 0x4000);
+
+	entry::list_type& file_prio = rd["file_priority"].list();
+	for (int i = 0; i < 100; ++i)
+	{
+		file_prio.push_back(entry(0));
+	}
+
+	std::string pieces(ti->num_pieces(), '\x01');
+	rd["pieces"] = pieces;
+
+	std::string pieces_prio(ti->num_pieces(), '\x01');
+	rd["piece_priority"] = pieces_prio;
+
+	bencode(back_inserter(p.resume_data), rd);
+
+	torrent_handle h = ses.add_torrent(p);
+
+	torrent_status s = h.status();
+	TEST_EQUAL(s.total_wanted, 0);
+}
+
+void test_seed_mode(bool file_prio, bool pieces_have, bool piece_prio
+	, bool all_files_zero = false)
 {
 	fprintf(stderr, "test_seed_mode file_prio: %d pieces_have: %d piece_prio: %d\n"
 		, file_prio, pieces_have, piece_prio);
@@ -295,6 +333,13 @@ void test_seed_mode(bool file_prio, bool pieces_have, bool piece_prio)
 		// this should take it out of seed_mode
 		entry::list_type& file_prio = rd["file_priority"].list();
 		file_prio.push_back(entry(0));
+		if (all_files_zero)
+		{
+			for (int i = 0; i < 100; ++i)
+			{
+				file_prio.push_back(entry(0));
+			}
+		}
 	}
 
 	std::string pieces(ti->num_pieces(), '\x01');