From ad5203e77a7e437b0acf9cb408ebec95a083f0e8 Mon Sep 17 00:00:00 2001
From: Florian Renkin <frenkin@lrde.epita.fr>
Date: Mon, 13 Sep 2021 17:46:33 +0200
Subject: [PATCH] synthesis: Fix segfault when there is no output

* spot/twaalgos/synthesis.cc: here
* tests/python/synthesis.py: create a test
* tests/Makefile.am: add synthesis.py to the tests
---
 spot/twaalgos/synthesis.cc |  2 ++
 tests/Makefile.am          |  1 +
 tests/python/synthesis.py  | 49 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+)
 create mode 100644 tests/python/synthesis.py

diff --git a/spot/twaalgos/synthesis.cc b/spot/twaalgos/synthesis.cc
index 22f74f934..d9cc9be0a 100644
--- a/spot/twaalgos/synthesis.cc
+++ b/spot/twaalgos/synthesis.cc
@@ -876,6 +876,8 @@ namespace spot
 
     [](std::vector<std::string> sv, std::string msg)
       {
+        if (sv.size() < 2)
+          return;
         std::sort(sv.begin(), sv.end());
         const unsigned svs = sv.size() - 1;
         for (unsigned i = 0; i < svs; ++i)
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 21c33979f..73232ef7d 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -445,6 +445,7 @@ TESTS_python = \
   python/stutter.py \
   python/rs_like.py \
   python/sum.py \
+  python/synthesis.py \
   python/toparity.py \
   python/trival.py \
   python/tra2tba.py \
diff --git a/tests/python/synthesis.py b/tests/python/synthesis.py
new file mode 100644
index 000000000..da72b9868
--- /dev/null
+++ b/tests/python/synthesis.py
@@ -0,0 +1,49 @@
+# -*- mode: python; coding: utf-8 -*-
+# Copyright (C) 2021 Laboratoire de Recherche et Développement
+# de l'Epita
+#
+# This file is part of Spot, a model checking library.
+#
+# Spot is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# Spot is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+# License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import spot
+
+# A shared variable caused the 2nd call to create_game to give an incorrect
+# result.
+for i in range(0, 2):
+    gi = spot.game_info()
+    gi.s = spot.game_info.solver_LAR
+    game = spot.create_game("(Ga) <-> (Fb)", ["b"], gi)
+    assert not spot.solve_game(game)
+
+# A game can have only inputs
+game = spot.create_game("GFa", [])
+assert(game.to_str() == """HOA: v1
+States: 3
+Start: 0
+AP: 1 "a"
+acc-name: parity max odd 6
+Acceptance: 6 Inf(5) | (Fin(4) & (Inf(3) | (Fin(2) & (Inf(1) | Fin(0)))))
+properties: trans-labels explicit-labels state-acc colored complete
+properties: deterministic
+spot-state-player: 0 1 1
+--BODY--
+State: 0 {1}
+[!0] 1
+[0] 2
+State: 1 {4}
+[t] 0
+State: 2 {5}
+[t] 0
+--END--""")