Re: [TCLCORE] CFV: My final round for 8.6...

[Donal K. F. <don...@ma...>]

Jan Nijtmans wrote:
> Further on, I agree with Joe about the Tcl_NRAddCallback
> signature: it is overkill to have 4 clientData arguments,
> one would be sufficient. For use inside the core,
> there still is an internal variant with 4 arguments, so this
> change is easy: Just make Tcl NRAddCallback call
> TclNRAddCallback, but with NULL as the last 3 arguments.
> I considered giving Tcl_NRAddCallback a variable number of
> arguments, but I think that would needlessly complicate things.

I've written a few of the actual uses of that API, and can supply a bit
of grist to this mill. It is most certainly useful to be able to pass
more than one machine-word to the callback, and 4 covers a vast majority
of cases: keeping down the number of times you have to allocate memory
on the critical path is also a good idea.

IIRC, the number 4 was chosen because that was what it was convenient to
provide in the backing structure while retaining a fast allocator. Or
something like that.

Donal.