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: 103376,5997b4b7b514f689 X-Google-Attributes: gid103376,public From: fjh@murlibobo.cs.mu.OZ.AU (Fergus Henderson) Subject: Re: Really more GC talk (was: Reading a line of arbitrary length) Date: 1997/03/12 Message-ID: <5g5f1a$pep@mulga.cs.mu.OZ.AU>#1/1 X-Deja-AN: 224854498 References: <5ds40o$rpo@fg70.rz.uni-karlsruhe.de> <33032AE2.666F@mds.lmco.com> <1997Mar5.102140.1@eisner> <5flm4e$ngl@mulga.cs.mu.OZ.AU> <1997Mar6.075735.1@eisner> <5g2mmb$2nl@mulga.cs.mu.OZ.AU> Organization: Comp Sci, University of Melbourne Newsgroups: comp.lang.ada Date: 1997-03-12T00:00:00+00:00 List-Id: dewar@merv.cs.nyu.edu (Robert Dewar) writes: >Fergus said > ><only conservative garbage collection, and that implementations that use >non-conservative GC techniques cannot be standard-conforming. > >That still seems to me to be a potentially undesirable constraint to >place on standard-conforming implementations. >>> > >I can't figure out the strange misreading of the RM that leads to this >incorrect conclusion, but it is certainly an incorrect conclusion. >There is no such constraint in the RM. Suppose I pass an Ada access type to a C function and store the pointer in a C global variable, and suppose that the data pointed to is reachable only via that pointer. Can my combined C/Ada program be standard-conforming? If not, then I guess I'll just have to give up mixed-language programming. If so, then does the Ada standard allow the implementation to reclaim the memory? If so, please cite chapter and verse. If not, then this would place potentially undesirable constraints on implementations. In particular, it would prohibit non-conservative GC techniques -- or require them to non-conservatively collect the C code too, which is not feasible, due to the presence of undiscriminated unions. -- Fergus Henderson | "I have always known that the pursuit WWW: | of excellence is a lethal habit" PGP: finger fjh@128.250.37.3 | -- the last words of T. S. Garp.