Introduct a down_cast macro.

* src/misc/casts.hh: New file.
* src/misc/Makefile.am: Add it.
* iface/dve2/dve2.cc, iface/gspn/gspn.cc, iface/gspn/ssp.cc,
src/evtgba/explicit.cc, src/evtgba/product.cc, src/misc/casts.hh,
src/tgba/state.hh, src/tgba/statebdd.cc, src/tgba/taatgba.cc,
src/tgba/taatgba.hh, src/tgba/tgbabddconcrete.cc,
src/tgba/tgbaexplicit.cc, src/tgba/tgbaexplicit.hh,
src/tgba/tgbakvcomplement.cc, src/tgba/tgbaproduct.cc,
src/tgba/tgbasafracomplement.cc, src/tgba/tgbasgba.cc,
src/tgba/tgbatba.cc, src/tgba/tgbaunion.cc, src/tgba/wdbacomp.cc,
src/tgbaalgos/ndfs_result.hxx, src/tgbaalgos/reductgba_sim.cc,
src/tgbaalgos/reductgba_sim_del.cc: Use down_cast when
appropriate.

src/misc/casts.hh

@@ -0,0 +1,40 @@
+// Copyright (C) 2011 Laboratoire de Recherche et Développement
+// de l'Epita (LRDE).
+//
+// 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 2 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 Spot; see the file COPYING.  If not, write to the Free
+// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+
+#ifndef SPOT_MISC_CASTS_HH
+#  define SPOT_MISC_CASTS_HH
+
+
+// We usually write code like
+//   subclass* i = down_cast<subclass*>(m);
+//   assert(i);
+//   ... use i ...
+// When NDEBUG is set, the down_cast is a fast static_cast
+// and the assert has no effect.
+// Otherwise, the down_cast is a dynamic_cast and may return 0
+// on error, which the assert catches.
+
+#if NDEBUG
+# define down_cast static_cast
+#else
+#  define down_cast dynamic_cast
+#endif
+
+#endif // SPOT_MISC_CASTS_HH