A workaround to detect dangling object references in Commands and

Interface. Now Object's destructor sets its id to 0xbadbeef, which
makes it possible to detect dangling references.

Author: BrunoLevy

src/lib/OGF/gom/lua/lua_graphite_object.cpp

@@ -561,9 +561,15 @@ namespace OGF {
 
 	Object* lua_tographite(lua_State* L, int index) {
 	    geo_debug_assert(lua_isgraphite(L,index));
-	    return static_cast<GraphiteRef*>(
+	    Object* result = static_cast<GraphiteRef*>(
 		lua_touserdata(L,index)
 	    )->object;
+	    if(result->id() == Object::INVALID_ID) {
+		Logger::warn("GOM") << "Reference to invalid Object"
+				    << std::endl;
+		result = nullptr;
+	    }
+	    return result;
 	}
 
 

src/lib/OGF/gom/types/object.cpp

@@ -90,6 +90,7 @@ namespace OGF {
 		id_to_object_ = nullptr;
 	    }
 	}
+	id_ = static_cast<unsigned int>(0xbadbeef);
     }
 
     void Object::disconnect() {

src/lib/OGF/gom/types/object.h

@@ -64,6 +64,9 @@ namespace OGF {
     gom_attribute(abstract,"true")
     gom_class GOM_API Object : public Counted {
     public:
+	static constexpr unsigned int INVALID_ID
+	    = static_cast<unsigned int>(0xbadbeef);
+
         /**
          * \brief Object constructor.
 	 * \param[in] transient if true, the object is transient.

src/lib/OGF/scene_graph/commands/commands.cpp

@@ -60,6 +60,10 @@ namespace OGF {
         grob_ = grob ;
     }
 
+    Grob* Interface::get_grob() const {
+	return ((grob_->id() == Object::INVALID_ID) ? nullptr : grob_);
+    }
+
     SceneGraph* Interface::scene_graph() const {
         return grob_->scene_graph() ;
     }
@@ -171,7 +175,7 @@ namespace OGF {
     }
 
     Interpreter* Commands::interpreter() {
-	if(get_grob() == nullptr) {
+	if(get_grob() == nullptr || get_grob()->id() == Object::INVALID_ID) {
 	    return nullptr;
 	}
 	return get_grob()->interpreter();

src/lib/OGF/scene_graph/commands/commands.h

@@ -111,9 +111,7 @@ namespace OGF {
          * \brief Gets the current Grob
          * \return a pointer to the current Grob
          */
-        Grob* get_grob() const {
-            return grob_;
-        }
+        Grob* get_grob() const;
 
     private:
         Grob* grob_;