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=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM autolearn=unavailable autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail From: Victor Porton Newsgroups: comp.lang.ada Subject: Re: Allocators design flaw Date: Sat, 14 Oct 2017 16:59:05 +0300 Organization: Aioe.org NNTP Server Message-ID: References: NNTP-Posting-Host: 8U0x309/ia0QUzusgm/krA.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit X-Complaints-To: abuse@aioe.org User-Agent: KNode/4.14.10 X-Notice: Filtered by postfilter v. 0.8.2 Xref: news.eternal-september.org comp.lang.ada:48450 Date: 2017-10-14T16:59:05+03:00 List-Id: Simon Wright wrote: > Victor Porton writes: > >> It is impossible to properly implement an allocator through a C function >> (such as raptor_alloc_memory() from Raptor C library) which allocates a >> struct and returns the pointer to the allocated struct. >> >> It is because RM13.11(21.5/3) "The Alignment parameter is a nonzero >> integral multiple of D'Alignment..." >> >> (If it were "The Alignment parameter is equal to D'Alignment", then we >> would be able just to check (in Allocate procedure implementation) that >> >> pragma Assert(Dummy_Record'Alignment mod Alignment = 0); >> -- where Dummy_Record is an arbitrary C-convention record >> -- (as all C records have the same alignment reqs) > > See the arguments in the AI: > http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai05s/ai05-0193-1.txt?rev=1.8&raw=N > >> So Alignment parameter may be arbitrarily big and the C function >> alignment may not conform to it. > > No bigger than 'Max_Alignment_For_Allocation. This does not help. >> Let us think how to work around (in Ada 202x) of this design flaw. > > If the C struct needs alignment greater than that of the elements of > which it is composed (see the AI for example) it would have it. "it would have it"? What this sequence of English words mean? -- Victor Porton - http://portonvictor.org