Option #1 was what I was suggesting in the meeting two weeks ago - if this starts to recurse too deeply, create a worklist - which should give you the same result.
If you switch to .Equals - you might get a different result … thanks, Karen > On Jan 31, 2019, at 1:46 PM, fo...@univ-mlv.fr wrote: > > > > De: "John Rose" <john.r.r...@oracle.com> > À: "Remi Forax" <fo...@univ-mlv.fr> > Cc: "Karen Kinnear" <karen.kinn...@oracle.com>, "valhalla-spec-experts" > <valhalla-spec-experts@openjdk.java.net> > Envoyé: Jeudi 31 Janvier 2019 19:05:33 > Objet: Re: An example of substituability test that is recursive > On Jan 31, 2019, at 6:34 AM, fo...@univ-mlv.fr <mailto:fo...@univ-mlv.fr> > wrote: > > The other solution is to say that == should do an upcall to equals (after the > null checking and the class checking), if equals throw a StackOverflow, it's > the expected behavior because the user is in control of that behavior. > > What you are doing here, I think, is exposing a requirement > that we *don't* use the control stack for recursion on subst. > testing (or hashing). That's a reasonable requirement. > It leads to a worklist algorithm for doing this tricky thing, > just like we had to do many times in the JIT. > > > > IMO that the other solution, > solution 1: you use a worklist (and also perhaps a marking algorithm to avoid > to crawle the DAG) > solution 2: you claim it's too complex and you just let the user deal with it > by calling equals() (and provide a way for a user to call the default subst). > > Rémi >
