+
+namespace s4u {
+class Activity;
+class Actor;
+using ActorPtr = boost::intrusive_ptr<Actor>;
+XBT_PUBLIC void intrusive_ptr_release(Actor* actor);
+XBT_PUBLIC void intrusive_ptr_add_ref(Actor* actor);
+class Comm;
+using CommPtr = boost::intrusive_ptr<Comm>;
+XBT_PUBLIC void intrusive_ptr_release(Comm* c);
+XBT_PUBLIC void intrusive_ptr_add_ref(Comm* c);
+class Engine;
+class Exec;
+using ExecPtr = boost::intrusive_ptr<Exec>;
+XBT_PUBLIC void intrusive_ptr_release(Exec* e);
+XBT_PUBLIC void intrusive_ptr_add_ref(Exec* e);
+class Host;
+class Link;
+class Mailbox;
+using MailboxPtr = boost::intrusive_ptr<Mailbox>;
+XBT_PUBLIC void intrusive_ptr_release(Mailbox* m);
+XBT_PUBLIC void intrusive_ptr_add_ref(Mailbox* m);
+class Mutex;
+XBT_PUBLIC void intrusive_ptr_release(Mutex* m);
+XBT_PUBLIC void intrusive_ptr_add_ref(Mutex* m);
+class NetZone;
+class VirtualMachine;
+class File;
+class Storage;
+} // namespace s4u
+
+namespace config {
+template <class T> class Flag;
+}
+
+namespace kernel {
+class EngineImpl;
+namespace actor {
+class ActorImpl;
+using ActorImplPtr = boost::intrusive_ptr<ActorImpl>;
+} // namespace actor
+
+namespace activity {
+ class ActivityImpl;
+ using ActivityImplPtr = boost::intrusive_ptr<ActivityImpl>;
+ XBT_PUBLIC void intrusive_ptr_add_ref(ActivityImpl* activity);
+ XBT_PUBLIC void intrusive_ptr_release(ActivityImpl* activity);
+
+ class ConditionVariableImpl;
+
+ class CommImpl;
+ using CommImplPtr = boost::intrusive_ptr<CommImpl>;
+ class ExecImpl;
+ using ExecImplPtr = boost::intrusive_ptr<ExecImpl>;
+ class IoImpl;
+ using IoImplPtr = boost::intrusive_ptr<IoImpl>;
+ class MutexImpl;
+ using MutexImplPtr = boost::intrusive_ptr<MutexImpl>;
+ class RawImpl;
+ using RawImplPtr = boost::intrusive_ptr<RawImpl>;
+ class SleepImpl;
+ using SleepImplPtr = boost::intrusive_ptr<SleepImpl>;
+
+ class MailboxImpl;
+}
+namespace context {
+class Context;
+class ContextFactory;
+} // namespace context
+namespace lmm {
+class Element;
+class Variable;
+class Constraint;
+class ConstraintLight;
+class System;
+}
+namespace resource {
+class Action;
+class Model;
+class Resource;
+class TraceEvent;
+class LinkImpl;
+class NetworkAction;
+}
+namespace routing {
+class ClusterCreationArgs;
+class LinkCreationArgs;
+class NetPoint;
+class NetZoneImpl;
+class RouteCreationArgs;
+}
+} // namespace kernel
+namespace simix {