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
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[MJ] thinks a list like this is a dangerous thing. Safest thing is to do an [Tcl_IncrRefCount] at the beginning and a [Tcl_DecrRefCount] at the end. There are several reasons why I think this is better:

   * The performance penalty is negligible
   * It always works even if the routine does do a [Tcl_DecrRefCount] so there is no need to keep referring to this list
   * It will work in other versions of Tcl where the functions in this list may have been changed so they do manipulate the refcount

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[Category Internals]