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=0.1 required=5.0 tests=AC_FROM_MANY_DOTS,BAYES_00, INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,86ec22e070e319c0 X-Google-Attributes: gid103376,public From: Jeff Carter Subject: Re: How do I get this to work?? Date: 1999/01/20 Message-ID: <36A5DB4E.CC5C88A@spam.innocon.com>#1/1 X-Deja-AN: 434802857 Content-Transfer-Encoding: 7bit References: <77vi4q$o7l$1@nnrp1.dejanews.com> <782rcn$kev$1@nnrp1.dejanews.com> Content-Type: text/plain; charset=us-ascii Organization: Innovative Concepts, Inc. Mime-Version: 1.0 Newsgroups: comp.lang.ada Date: 1999-01-20T00:00:00+00:00 List-Id: robert_dewar@my-dejanews.com wrote: > > In article , > warwicks@telusplanet.net (Chris Warwick) wrote: > > > Of the Ada compilers I have used, the > > unchecked_deallocation on all of them > > was to set the pointer to 0 and carry on (i.e., no calls > > to deallocate, no > > storing the un-used memory for later re-allocation by the > > Ada program). When I > > first stumbled into this I was told that this was for > > safety reasons. It may > > have been that I have been using safety critical versions > > of these Ada > > compilers, and "standard" compilers are different... > > > > I have already discussed this with Chris. He claimed that > VADS behaved as above, which I know to be incorrect, and > he claimed that Alsys behaved as above. I particularly know > the latter claim to be false, since I wrote that code! The > one thing in Alsys that he may be referring to was that for > certain cases of small blocks in local collections, we > deferred collecting the storage till scope exit, but that > is the only case where there was even a deferral of the > free operation. > > The claim that this has to do with safety is just wrong. > > And as for safety critical subsets, clearly these do not > even allow Unchecked_Deallocation in the first place. > > Clearly Chris's statements here are based on > misinformation, or misinterpretation of some kind, > and it is important not to be mislead by them. > > Unchecked_Deallocation works just fine on all Ada compilers > and always has, it is as reliable as free in C (and indeed > on many compilers translates directly into a free call). > FWIW, the first Ada compiler I used was the Rolm compiler for the Data General Eclipse in 1984, which claimed to be the first validated Ada-83 compiler. This machine allocated an unheard-of (in 1984) 4 GB of virtual memory for every process. I was told that this compiler's Unchecked_Deallocation only set the access variable to null without reusing the allocated memory, because no one could ever use up 4 GB. This compiler was used only for training and I never verified this statement. This is the only compiler I have used in the last 15 years that did not deallocate memory. However, I was also told that this compiler was the reason Booch included memory-managed components in his components. There seems to be a lot of hearsay in this post ... -- Jeff Carter E-mail: carter commercial-at innocon [period | full stop] com "We burst our pimples at you." Monty Python & the Holy Grail