For C code that calls Tcl public routines that
accept ''(Tcl_Obj *)'' arguments, the most
efficient techniques for reference count
management rely on knowing which routines
are known safe to pass a zero-ref 
Tcl_Obj to.

These are the routines that do not make any
call to Tcl_DecrRefCount() on
the argument, and do not call anything else
that does.  Here's the start of a list.
Please add to it:

  * Tcl_GetStringFromObj()
  * Tcl_GetIndexFromObj()
  * Tcl_GetIndexFromObjStruct()