Dear all, I seem to be having a problem with unarchiving a user-defined class on Mac OS X. The problem is that the static member class_info<registered_class_options>::first is (besides inside the GiNaC dynamic library) also created within my executable. This second version is then used when registering my own class, so that my own class does not appear in the linked list of which *(class_info<registered_class_options>::first) is the first element. I debugged this by printing both the address of first and the name of the class being registered from the constructor of class_info and the for my own class the address of first turned out to be different. The consequence of this is that members of my own class cannot be unarchived. The problem does not occur on Linux. Anyone any bright ideas? Should this be considered a bug GiNaC? Does anyone know a combination of linker flags that can prevent this? Best wishes, Chris