try to solve the -Wundefined-var-template thing with clang

diff --git a/src/s4u/s4u_Activity.cpp b/src/s4u/s4u_Activity.cpp
index 159ac3e..d9c236a 100644 (file)
--- a/src/s4u/s4u_Activity.cpp
+++ b/src/s4u/s4u_Activity.cpp
@@ -27,7 +27,7 @@ namespace s4u {
 xbt::signal<void(Activity&)> Activity::on_veto;
 xbt::signal<void(Activity const&)> Activity::on_suspended;
 xbt::signal<void(Activity const&)> Activity::on_resumed;
-template<class AnyActivity> xbt::signal<void(AnyActivity const&)> Activity_T<AnyActivity>::on_completion;
+template<class AnyActivity> extern xbt::signal<void(AnyActivity const&)> Activity_T<AnyActivity>::on_completion;
 
 std::set<Activity*>* Activity::vetoed_activities_ = nullptr;