I think it's both, but that may not be entirely true.

XS is a series of macros, yes, but it's also a sort of preprocessor template system for C, so it's theoretically possible to emit different code for different versions of Perl.

In practice, that sounds really difficult to implement.

My take on this is that it depends on the objective.

If the goal is to simplify accessing Perl internals for module authors, creating a wrapper macro/class ( XSS = XS-Simple ? ) for a new API seems the way to go. Preferably in a modular/ linkable way. Since this would rely on standardized XS it should also be backwards compatible.

Changing the XS implementation is another beast, while this might benefit core devs I doubt there is a mid-term return of investment justifying the risk.

Again, theoretical thoughts. If I'm wrong about the details, please enlighten me. :)

Cheers Rolf
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Wikisyntax for the Monastery}