sepsets: fix infinite loop

* tests/core/sepsets.test: New test case.
* spot/twaalgos/sepsets.cc: Fix the code.
* NEWS: Mention the problem.

NEWS

@@ -1,6 +1,9 @@
 New in spot 2.7.3.dev (not yet released)
 
-  Nothing yet.
+  Bugs fixed:
+
+  - separate_sets_here() (and therefore autfilt --separate-sets) could
+    loop infinitely on some inputs.
 
 New in spot 2.7.3 (2019-04-19)
 

spot/twaalgos/sepsets.cc

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2015-2018 Laboratoire de Recherche et
+// Copyright (C) 2015-2019 Laboratoire de Recherche et
 // Développement de l'Epita.
 //
 // This file is part of Spot, a model checking library.
@@ -69,8 +69,7 @@ namespace spot
             break;
           case acc_cond::acc_op::Fin:
           case acc_cond::acc_op::FinNeg:
-            if (!(pos[-1].mark & common))
-              break;
+            if (pos[-1].mark & common)
               for (auto p: map)
                 if (pos[-1].mark & p.first)
                   {

tests/core/sepsets.test

@@ -1,6 +1,6 @@
 #!/bin/sh
 # -*- coding: utf-8 -*-
-# Copyright (C) 2015 Laboratoire de Recherche et Développement de
+# Copyright (C) 2015, 2019 Laboratoire de Recherche et Développement de
 # l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -39,6 +39,16 @@ State: 2
 [!0&1&!2] 1
 [0&!2] 2 {0 1}
 --END--
+HOA: v1
+States: 1
+Start: 0
+AP: 3 "p0" "p1" "p2"
+Acceptance: 3 (Fin(1) | Inf(0)) & (Fin(2) | Inf(1))
+properties: trans-labels explicit-labels state-acc deterministic
+--BODY--
+State: 0 {0 1 2}
+[0&!1&!2] 0
+--END--
 EOF
 
 cat >expected <<EOF
@@ -60,6 +70,16 @@ State: 2
 [!0&1&!2] 1
 [0&!2] 2 {0 1 2 3}
 --END--
+HOA: v1
+States: 1
+Start: 0
+AP: 3 "p0" "p1" "p2"
+Acceptance: 4 (Fin(3) | Inf(0)) & (Fin(2) | Inf(1))
+properties: trans-labels explicit-labels state-acc deterministic
+--BODY--
+State: 0 {0 1 2 3}
+[0&!1&!2] 0
+--END--
 EOF
 
 run 0 autfilt --separate-sets in -H > out