diff --git a/ChangeLog b/ChangeLog
index 06f38ca50..8b993e10f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2004-04-13  Alexandre Duret-Lutz  <adl@src.lip6.fr>
+
+	* src/tgbaalgo/semptinesscheck.hh (scc_stack): New class, extracted
+	from ...
+	(emptiness_check): ... here.
+	(emptiness_check::root): Redefined as a scc_stack object.
+	* src/tgbaalgos/emptinesscheck.cc: Adjust.
+
 2004-04-05  Alexandre Duret-Lutz  <adl@src.lip6.fr>
 
 	* src/tgbaalgos/emptinesscheck.cc (emptiness_check::complete_cycle):
diff --git a/src/tgbaalgos/emptinesscheck.cc b/src/tgbaalgos/emptinesscheck.cc
index eb9a47913..fc2233296 100644
--- a/src/tgbaalgos/emptinesscheck.cc
+++ b/src/tgbaalgos/emptinesscheck.cc
@@ -29,14 +29,45 @@
 
 namespace spot
 {
-  typedef std::pair<const spot::state*, tgba_succ_iterator*> pair_state_iter;
 
-  emptiness_check::connected_component::connected_component(int i)
+  scc_stack::connected_component::connected_component(int i)
   {
     index = i;
     condition = bddfalse;
   }
 
+  scc_stack::connected_component&
+  scc_stack::top()
+  {
+    return s.top();
+  }
+
+  void
+  scc_stack::pop()
+  {
+    s.pop();
+  }
+
+  void
+  scc_stack::push(int index)
+  {
+    s.push(connected_component(index));
+  }
+
+  size_t
+  scc_stack::size() const
+  {
+    return s.size();
+  }
+
+  bool
+  scc_stack::empty() const
+  {
+    return s.empty();
+  }
+
+  typedef std::pair<const spot::state*, tgba_succ_iterator*> pair_state_iter;
+
   bool
   emptiness_check::connected_component_set::has_state(const state* s) const
   {
@@ -136,7 +167,7 @@ namespace spot
     {
       state* init = aut_->get_init_state();
       h[init] = 1;
-      root.push(connected_component(1));
+      root.push(1);
       arc.push(bddfalse);
       tgba_succ_iterator* iter = aut_->succ_iter(init);
       iter->first();
@@ -195,7 +226,7 @@ namespace spot
 	    // Yes.  Number it, stack it, and register its successors
 	    // for later processing.
 	    h[dest] = ++num;
-	    root.push(connected_component(num));
+	    root.push(num);
 	    arc.push(acc);
 	    tgba_succ_iterator* iter = aut_->succ_iter(dest);
 	    iter->first();
@@ -411,7 +442,7 @@ namespace spot
 	successor succ = queue.front();
 	queue.pop_front();
 	h[succ.s] = ++num;
-	root.push(connected_component(num));
+	root.push(num);
 	arc.push(succ.acc);
 	todo.push(pair_state_successors(succ.s, succ_queue()));
 	succ_queue& new_queue = todo.top().second;
diff --git a/src/tgbaalgos/emptinesscheck.hh b/src/tgbaalgos/emptinesscheck.hh
index 8b612b34b..e7a943113 100644
--- a/src/tgbaalgos/emptinesscheck.hh
+++ b/src/tgbaalgos/emptinesscheck.hh
@@ -32,6 +32,30 @@
 namespace spot
 {
 
+  class scc_stack
+  {
+  public:
+    struct connected_component
+    {
+      // During the Depth path we keep the connected component that we met.
+    public:
+      connected_component(int index = -1);
+
+      int index;
+      /// The bdd condition is the union of all acceptance conditions of
+      /// transitions which connect the states of the connected component.
+      bdd condition;
+    };
+
+    connected_component& top();
+    void pop();
+    void push(int index);
+    size_t size() const;
+    bool empty() const;
+
+    std::stack<connected_component> s;
+  };
+
   /// \brief Check whether the language of an automate is empty.
   ///
   /// This is based on the following paper.
@@ -100,19 +124,7 @@ namespace spot
 
   private:
 
-    struct connected_component
-    {
-      // During the Depth path we keep the connected component that we met.
-    public:
-      connected_component(int index = -1);
-
-      int index;
-      /// The bdd condition is the union of all acceptance conditions of
-      /// transitions which connect the states of the connected component.
-      bdd condition;
-    };
-
-    struct connected_component_set: public connected_component
+    struct connected_component_set: public scc_stack::connected_component
     {
       typedef Sgi::hash_set<const state*,
 			    state_ptr_hash, state_ptr_equal> set_type;
@@ -125,7 +137,7 @@ namespace spot
     };
 
     const tgba* aut_;
-    std::stack<connected_component> root;
+    scc_stack root;
     state_sequence suffix;
     cycle_path period;