routines safe for zero-ref objs

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

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

Category Internals