Tcl_RegisterObjType , a part of the Tcl C API, registers a new Tcl value type in the table of all value types that Tcl_GetObjType can look up by name.


official reference


I think experience has shown that it's best for a Tcl_ObjType author not to call Tcl_RegisterObjType(), but instead to provide a My_GetFooFromObj() routine. objtype registration is an error wrapped in a mistake... name conflicts opportunities, with no sensible collision resolution. All to the endpoint of issuing an invitation to intrude into private spaces. Bleah. The main positive value of the routine Tcl_RegisterObjType() is that it is a routine name by which you can call up the man page that documents the Tcl_ObjType interface.
DGP, Tcl Chatroom, 2014-05-05
By the way, Tcl_RegisterObjType is deprecated because its only use is Tcl_ConvertToType... and because its "design" was fundamentally broken.
KBK, Tcl Chatroom, 2014-06-19