diff --git a/ChangeLog b/ChangeLog
index 5107c6ecd..41a799d84 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2003-06-28  Alexandre Duret-Lutz  <aduret@src.lip6.fr>
+
+	Fix errors reported by ICC.
+
+	* src/tgba/state.hh (state_ptr_less_than::operator()): Make it const.
+	* src/tgba/tgbaproduct.cc: Include string.hh.
+	* src/ltlast/multop.hh (multop::add, multop::add_sorted): Do
+	not use qualified names in declarations.
+	* m4/gccwarn.m4 (CF_GXX_WARNINGS): Fix GXX test.
+	* src/ltlenv/defaultenv.hh, src/ltlenv/defaultenv.cc,
+	src/ltlenv/environment.hh: Add virtual destructors.
+
 2003-06-26  Alexandre Duret-Lutz  <aduret@src.lip6.fr>
 
 	* Makefile.am (EXTRA_DIST): Add HACKING.
diff --git a/m4/gccwarn.m4 b/m4/gccwarn.m4
index 5601050ea..1fcdf8f63 100644
--- a/m4/gccwarn.m4
+++ b/m4/gccwarn.m4
@@ -14,7 +14,7 @@ dnl A few other options have been left out because they are annoying in C++.
 
 
 AC_DEFUN([CF_GXX_WARNINGS],
-[if test -n "$GXX"; then
+[if test "x$GXX" = xyes; then
   AC_CACHE_CHECK([for g++ warning options], ac_cv_prog_gxx_warn_flags,
   [
   cat > conftest.$ac_ext <<EOF
diff --git a/src/ltlast/multop.hh b/src/ltlast/multop.hh
index a311929ab..e5ec1b3b7 100644
--- a/src/ltlast/multop.hh
+++ b/src/ltlast/multop.hh
@@ -86,8 +86,8 @@ namespace spot
 
       multop(type op, vec* v);
       static multop* instance(type op, vec* v);
-      static vec* multop::add(type op, vec* v, formula* f);
-      static void multop::add_sorted(vec* v, formula* f);
+      static vec* add(type op, vec* v, formula* f);
+      static void add_sorted(vec* v, formula* f);
 
       virtual ~multop();
 
diff --git a/src/ltlenv/defaultenv.cc b/src/ltlenv/defaultenv.cc
index c7a495108..21c281138 100644
--- a/src/ltlenv/defaultenv.cc
+++ b/src/ltlenv/defaultenv.cc
@@ -6,6 +6,10 @@ namespace spot
   namespace ltl
   {
 
+    default_environment::~default_environment()
+    {
+    }
+
     formula*
     default_environment::require(const std::string& s)
     {
diff --git a/src/ltlenv/defaultenv.hh b/src/ltlenv/defaultenv.hh
index 99963033b..ab5d4dc80 100644
--- a/src/ltlenv/defaultenv.hh
+++ b/src/ltlenv/defaultenv.hh
@@ -17,6 +17,7 @@ namespace spot
     class default_environment : public environment
     {
     public:
+      virtual ~default_environment();
       virtual formula* require(const std::string& prop_str);
       virtual const std::string& name();
 
diff --git a/src/ltlenv/environment.hh b/src/ltlenv/environment.hh
index 534506a85..5720e6275 100644
--- a/src/ltlenv/environment.hh
+++ b/src/ltlenv/environment.hh
@@ -35,6 +35,11 @@ namespace spot
       /// Get the name of the environment.
       virtual const std::string& name() = 0;
 
+      virtual
+      ~environment()
+      {
+      };
+
       // FIXME: More functions will be needed later, but
       // it's enough for now.
     };
diff --git a/src/tgba/state.hh b/src/tgba/state.hh
index 2ddbe2cc2..75fcbc0e2 100644
--- a/src/tgba/state.hh
+++ b/src/tgba/state.hh
@@ -63,7 +63,7 @@ namespace spot
   struct state_ptr_less_than
   {
     bool
-    operator()(const state* left, const state *right)
+    operator()(const state* left, const state *right) const
     {
       return left->compare(right) < 0;
     }
diff --git a/src/tgba/tgbaproduct.cc b/src/tgba/tgbaproduct.cc
index 8e432c687..c1e56ca09 100644
--- a/src/tgba/tgbaproduct.cc
+++ b/src/tgba/tgbaproduct.cc
@@ -1,6 +1,7 @@
 #include "tgbaproduct.hh"
 #include "tgbatranslateproxy.hh"
 #include "dictunion.hh"
+#include <string>
 #include <cassert>
 
 namespace spot