From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,2308afbbe4ecec0b X-Google-Attributes: gid103376,public From: Brian Rogoff Subject: Re: Subverting 'Access for Sub-programs Date: 1999/08/10 Message-ID: #1/1 X-Deja-AN: 511307254 References: <7ocqru$rrm$1@nnrp1.deja.com> <7oeini$1pb$1@nnrp1.deja.com> Content-Type: TEXT/PLAIN; charset=US-ASCII X-Trace: nntp1.ba.best.com 934341215 204 bpr@206.184.139.136 MIME-Version: 1.0 Newsgroups: comp.lang.ada Date: 1999-08-10T00:00:00+00:00 List-Id: On Mon, 9 Aug 1999, Robert A Duff wrote: > Brian Rogoff writes: > > > So, only allow this for descendants of (possibly limited) Controlled > > types, or some similar special type? > > I don't see how that helps. If you have a global "type Ptr is access > all Something'Class", and you have a (illegal in Ada) type extension > local to some procedure, then you could end up with a global pointer > referencing an object of the local type (ie with the local 'Tag). > Finalizing it doesn't make any difference -- you still have a pointer to > a thing that contains dangling pointers (to the primitive ops). Yup, I know you can't use finalization to get this; I thought you were proposing a similar "distinguished tagged type" mechanism analogous to controlled types for nested extensions, but on rereading what you wrote I think that I must have hallucinated it :-). In any case, I still think nested type extensions are a lot less useful than a direct downward funarg capability. -- Brian