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Groups > comp.lang.c > #403178
| From | David Brown <david.brown@hesbynett.no> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: AVL tree insertion - programming exercise |
| Date | 2026-10-15 09:28 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <11apvau$25qhp$1@dont-email.me> (permalink) |
| References | (3 earlier) <86v775h9o2.fsf@linuxsc.com> <11am74c$54g$1@reader2.panix.com> <11amvh2$14pou$3@kst.eternal-september.org> <11anbq5$16fmd$1@dont-email.me> <11aovg9$1t8gq$1@kst.eternal-september.org> |
On 15/10/2026 00:25, Keith Thompson wrote: > David Brown <david.brown@hesbynett.no> writes: >> On 14/10/2026 06:13, Keith Thompson wrote: >>> cross@spitfire.i.gajendra.net (Dan Cross) writes: >>>> In article <86v775h9o2.fsf@linuxsc.com>, >>>> Tim Rentsch <tr.17687@z991.linuxsc.com> wrote: >>>>> cross@spitfire.i.gajendra.net (Dan Cross) writes: >>> [...] >>>>>> I don't think this is true anymore, as of C23. Here's the >>>>>> relevant text from n3220, sec 7.24.3, describing the return >>>>>> value from `malloc` et al: >>>>>> >>>>>> |The pointer returned if the allocation succeeds is suitably >>>>>> |aligned so that it may be assigned to a pointer to any type of >>>>>> |object with a fundamental alignment requirement and size less >>>>>> |than or equal to the size requested. >>>>>> >>>>>> This sentence is somewhat ambiguous because it's unclear whether >>>>>> the "less than or equal to the size requested" criteria applies >>>>>> to both the pointer type's size _and_ fundamental alignment >>>>>> requirement, or _just_ the size, [...] >>>>> >>>>> It's poorly constructed but in English it has only one >>>>> grammatical parse. >>>> >>>> Nope. Not even close. >>> >>> I think Tim is right about there being only one grammatical parse. >>> I'll try to use indentation to indicate (imperfectly) how I parse >>> it: >>> >>> The pointer returned if the allocation succeeds >>> is suitably aligned so that >>> it may be assigned to a pointer to any type of object >>> with >>> a fundamental alignment requirement >>> and· >>> size less than or equal to the size requested. >>> >>> So "a fundamental alignment requirement" and "size less than or equal >>> to the size requested" are parallel requirements, both applying to >>> the type of the pointed-to object. >>> >>> I do see a problem with the size requirement being *under* the >>> "suitably aligned" requirement. It wrongly implies that satisfying >>> the size requirement contributes to the "suitably aligned" requirement. >>> But that's not an ambiguous parse. >>> >>> Do you see a different way to parse the sentence? >> >> I do. "Operators" in English do not have the same clearly defined >> grammar rules as operators in C : >> >> The pointer returned if the allocation succeeds >> is suitably aligned so that >> it may be assigned to a pointer to any type of object >> with >> a fundamental alignment requirement >> and >> size >> less than or equal to the size requested. >> >> equivalent to : >> >> The pointer returned if the allocation succeeds >> is suitably aligned so that >> it may be assigned to a pointer to any type of object >> with >> a fundamental alignment requirement >> less than or equal to the size requested. >> and >> size >> less than or equal to the size requested. >> >> If you consider "fundamental alignment requirement" as evaluating to a >> number - the result of "alignas" - then I think this parse is also >> possible. I would even go as far as to say this was the intended >> parsing, because the parsing you gave above would mean the paragraph >> only applies to "objects with a fundamental alignment requirement" - >> and all complete object types have alignment requirements. > > I think you're missing the fact that "fundamental alignment" is a > defined term. N3220 6.2.8p2: > > A *fundamental alignment* is a valid alignment less than or equal to > alignof(max_align_t). > I am aware of that definition, and did not miss it. > And p3: > > An *extended alignment* is represented by an alignment greater > than alignof(max_align_t). It is implementation-defined whether > any extended alignments are supported and the storage durations > for which they are supported. A type having an extended alignment > requirement is an *over-aligned* type. Again, I read that too. > > The point is that malloc() cannot reliably allocate objects of > over-aligned types. C23 adds aligned_alloc() for that. Yes. > > I read "a fundamental alignment requirement" as a predicate; a > give object type always has an alignment, and may or may not have > a fundamental alignment requirement. Yes, I can see that is how you read it. And I also think that is the more obvious reading of the paragraph. I just don't think it is the only one. > > I think I now agree about the ambiguous parse, but I don't think it > matters, because an object type's alignment cannot be greater than its > size. I'm not sure that's stated explicitly, but otherwise arrays > wouldn't work (or the language would have to allow alignment gaps > between array elements). > >> Let us suppose a hypothetical implementation where CHAR_BIT == 8, >> sizeof(int) == 4, and alignof(int) == 8. > > That's not possible. Arrays of int cannot have gaps between the > elements. > That does sound right. An implementation that wanted to keep its 32-bit ints in 64-bit slots would have to have the size of the int as the full 64-bit, with 32 of those bits being padding. So my hypothetical implementation here could not exist. (Dan's recent post - as is often the case - is more complete and considered, and better researched than mine, so I defer to that for why the changes were made to the standard and how they should be interpreted.)
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AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-06 23:08 -0700
Re: AVL tree insertion - programming exercise fir <profesor.fir@gmail.com> - 2026-10-07 15:25 +0200
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-07 12:13 -0700
Re: AVL tree insertion - programming exercise fir <profesor.fir@gmail.com> - 2026-10-07 21:28 +0200
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-08 05:31 -0700
Re: AVL tree insertion - programming exercise fir <profesor.fir@gmail.com> - 2026-10-09 11:12 +0200
Re: AVL tree insertion - programming exercise fir <profesor.fir@gmail.com> - 2026-10-09 11:12 +0200
Re: AVL tree insertion - programming exercise BGB <cr88192@gmail.com> - 2026-10-07 20:10 -0500
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-08 05:56 -0700
Re: AVL tree insertion - programming exercise BGB <cr88192@gmail.com> - 2026-10-08 15:09 -0500
Re: AVL tree insertion - programming exercise fir <profesor.fir@gmail.com> - 2026-10-08 22:56 +0200
Re: AVL tree insertion - programming exercise BGB <cr88192@gmail.com> - 2026-10-08 17:29 -0500
Re: AVL tree insertion - programming exercise fir <profesor.fir@gmail.com> - 2026-10-09 09:56 +0200
Re: AVL tree insertion - programming exercise Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-09 01:39 +0200
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-09 00:03 -0700
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-08 23:53 -0700
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-09 10:34 +0200
Re: AVL tree insertion - programming exercise Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-09 12:27 +0200
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-09 12:59 +0200
Re: AVL tree insertion - programming exercise bart <bc@freeuk.com> - 2026-10-09 11:43 +0100
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-09 13:20 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-09 12:38 +0000
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-09 16:05 +0200
Re: AVL tree insertion - programming exercise Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-09 17:54 +0200
Re: AVL tree insertion - programming exercise Johann 'Myrkraverk' Oskarsson <johann@myrkraverk.invalid> - 2026-10-10 10:38 +0800
Re: AVL tree insertion - programming exercise ram@zedat.fu-berlin.de (Stefan Ram) - 2026-10-10 03:12 +0000
Re: AVL tree insertion - programming exercise Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-10-10 04:44 +0000
Re: AVL tree insertion - programming exercise "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-10 14:12 -0700
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-09 19:48 +0000
Re: AVL tree insertion - programming exercise scott@slp53.sl.home (Scott Lurndal) - 2026-10-09 23:18 +0000
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-10 15:27 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-12 18:26 +0000
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-12 21:17 +0200
Re: AVL tree insertion - programming exercise Michael S <already5chosen@yahoo.com> - 2026-10-09 17:47 +0300
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-09 16:48 +0000
Re: AVL tree insertion - programming exercise Michael S <already5chosen@yahoo.com> - 2026-10-10 19:08 +0300
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-10 18:29 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-10 17:44 +0000
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-10 23:22 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-10 17:43 +0000
Re: AVL tree insertion - programming exercise Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-10 20:35 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-10 19:36 +0000
Re: AVL tree insertion - programming exercise Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-10 22:08 +0200
Re: AVL tree insertion - programming exercise Michael S <already5chosen@yahoo.com> - 2026-10-10 23:21 +0300
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-10 20:55 +0000
Re: AVL tree insertion - programming exercise scott@slp53.sl.home (Scott Lurndal) - 2026-10-10 20:22 +0000
Re: AVL tree insertion - programming exercise Michael S <already5chosen@yahoo.com> - 2026-10-10 23:32 +0300
Re: AVL tree insertion - programming exercise scott@slp53.sl.home (Scott Lurndal) - 2026-10-11 15:24 +0000
Re: AVL tree insertion - programming exercise Bonita Montero <Bonita.Montero@gmail.com> - 2026-10-10 19:40 +0200
Re: AVL tree insertion - programming exercise Andrey Tarasevich <noone@noone.net> - 2026-10-10 12:39 -0700
Re: AVL tree insertion - programming exercise Michael S <already5chosen@yahoo.com> - 2026-10-10 23:00 +0300
Re: AVL tree insertion - programming exercise Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-10 22:28 +0200
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-10 19:02 -0700
Re: AVL tree insertion - programming exercise "chine.bleu" <chine.bleu@yahoo.com> - 2026-10-13 01:38 -0700
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-13 11:42 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-13 10:55 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-13 04:29 -0700
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-13 14:01 +0200
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-13 05:09 -0700
Re: AVL tree insertion - programming exercise antispam@fricas.org (Waldek Hebisch) - 2026-10-13 19:01 +0000
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-13 15:17 +0000
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-13 17:39 +0200
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-13 09:01 -0700
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-13 21:17 +0000
Re: AVL tree insertion - programming exercise "chine.bleu" <chine.bleu@yahoo.com> - 2026-10-13 18:01 -0700
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-13 21:13 -0700
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-14 09:43 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-14 20:11 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-14 15:25 -0700
Re: AVL tree insertion - programming exercise David Brown <david.brown@hesbynett.no> - 2026-10-15 09:28 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-14 14:13 +0000
Re: AVL tree insertion - programming exercise Janis Papanagnou <janis_papanagnou+ng@hotmail.com> - 2026-10-14 18:03 +0200
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-14 18:21 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-14 15:42 -0700
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-15 14:25 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-15 15:54 -0700
Re: AVL tree insertion - programming exercise Kaz Kylheku <046-301-5902@kylheku.com> - 2026-10-15 23:51 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-15 18:14 -0700
Re: AVL tree insertion - programming exercise Kaz Kylheku <046-301-5902@kylheku.com> - 2026-10-16 20:26 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-16 15:27 -0700
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-16 03:09 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-15 21:34 -0700
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-16 11:27 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-16 11:27 -0700
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-17 08:21 -0700
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-17 10:48 -0700
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-17 18:10 +0000
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-14 10:39 -0700
Re: AVL tree insertion - programming exercise scott@slp53.sl.home (Scott Lurndal) - 2026-10-13 17:15 +0000
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-13 21:30 +0000
Re: AVL tree insertion - programming exercise "chine.bleu" <chine.bleu@yahoo.com> - 2026-10-13 08:19 -0700
Re: AVL tree insertion - programming exercise "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-13 13:16 -0700
Re: AVL tree insertion - programming exercise Michael S <already5chosen@yahoo.com> - 2026-10-13 23:28 +0300
Re: AVL tree insertion - programming exercise James Kuyper <jameskuyper@alumni.caltech.edu> - 2026-10-13 06:20 -0400
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-13 14:34 +0000
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-13 20:45 -0700
Re: AVL tree insertion - programming exercise cross@spitfire.i.gajendra.net (Dan Cross) - 2026-10-14 14:25 +0000
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-14 20:54 -0700
Re: AVL tree insertion - programming exercise Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2026-10-14 22:47 -0700
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-15 04:42 -0700
Re: AVL tree insertion - programming exercise "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2026-10-15 14:07 -0700
Re: AVL tree insertion - programming exercise Tim Rentsch <tr.17687@z991.linuxsc.com> - 2026-10-13 03:52 -0700
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