Broken variable handling? about pyswip

[VorpalBlade]

I tried debugging this, and it seems the call to PL_get_chars in Variable.__init__ returns 0 and thus Variable.chars is never set. I assume this should be set to the print name of the variable and allow me to identify unique variables.

I don't have a minimal test case for this (though maybe I could try to write one), but this also happens with a more complex query:

In swipl:

refine(grandparent(Tgt0,Tgt1) :- true, [Tgt0,Tgt1], 0, 0, Results).
Results = [((grandparent(Tgt0, Tgt1):-parent(Tgt0, Tgt0)), 0, 1, [Tgt0, Tgt1]), ...]

And the same query via pyswip:

list(prolog.query(query))
Out[3]: 
[{'Tgt0': Variable(70),
  'Tgt1': Variable(73),
  'Results': [Functor(196877,2,:-(grandparent(Variable(83), Variable(84)), parent(Variable(85), Variable(86))),,(0, ,(1, [Variable(92), Variable(93)]))),
              ...]}]

As can be seen, here every time the same variable appears it has a unique identifier, which means the result is unusable for my application.

[VorpalBlade]

I found an (the?) issue. The values in core.py for CVT_VARIABLE, BUF_RING etc no longer matches SWI-Prolog.h.
I don't know the exact version where these changes were introduced but it seems new version logic is needed for this.