There is a missing refcount inc on sv before "SvRV_set(rv, sv);".
You're saying that newSVrv causes referenced material to be destroyed permaturely. I don't believe you.
In newSVrv, a new target SV is created at sv.c#l9268 in perl.git
. In a hypothetical setsv_rv you need to up the refcount of the EXISTING target SV that the reference will point to or the existing target SV will get garbage collected prematurely, and we arent making a weak reference here, or your following hv_store standard where the caller has to up the refcount (or do nothing with newSV) of the sv before passing to the func?