-XBT_PUBLIC() Checker* createLivenessChecker(Session& session);
-XBT_PUBLIC() Checker* createSafetyChecker(Session& session);
-XBT_PUBLIC() Checker* createCommunicationDeterminismChecker(Session& session);
-
+// External constructors so that the types (and the types of their content) remain hidden
+XBT_PUBLIC Checker* createLivenessChecker(Session& session);
+XBT_PUBLIC Checker* createSafetyChecker(Session& session);
+XBT_PUBLIC Checker* createCommunicationDeterminismChecker(Session& session);