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Re: Pre-main construction order in modules

From Michael S <already5chosen@yahoo.com>
Newsgroups comp.lang.c++
Subject Re: Pre-main construction order in modules
Date 2025-04-01 23:26 +0300
Organization A noiseless patient Spider
Message-ID <20250401232600.00002eb6@yahoo.com> (permalink)
References (5 earlier) <vse2ep$8iai$2@dont-email.me> <vse775$er2o$1@dont-email.me> <vsf99o$1hbqv$1@dont-email.me> <vsg4fq$2hn25$1@dont-email.me> <vshbgm$362k4$2@dont-email.me>

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On Tue, 1 Apr 2025 14:32:54 -0400
James Kuyper <jameskuyper@alumni.caltech.edu> wrote:

> On 01.04.2025 10:26, Muttley@DastardlyHQ.org wrote:
> > On Mon, 31 Mar 2025 19:42:48 -0400
> > James Kuyper <jameskuyper@alumni.caltech.edu> wibbled:  
> >> On 31.03.2025 17:01, Muttley@DastardlyHQ.org wrote:  
> >>> On Mon, 31 Mar 2025 15:39:53 +0300
> >>> Paavo Helde <eesnimi@osa.pri.ee> wibbled:  
> >>>> On 31.03.2025 12:09, Muttley@DastardlyHQ.org wrote:
> >>>> "If [initialization] is deferred, it strongly happens before any
> >>>> non-initialization odr-use of any non-inline function or
> >>>> non-inline variable defined in the same translation unit as the
> >>>> variable to be initialized."  
> >>>
> >>> Who writes this stuff? Its borderline gibberish.  
> >>
> >> Keep in mind that the key thing that makes this seem like
> >> gibberish is the use of precisely defined technical jargon, which
> >> is used for the same reason that jargon is used in many other
> >> contexts: it has a more precisely specified meaning than more
> >> informal wording would have had.
> >>
> >> Key pieces of jargon: "strongly happens before",
> >> "non-initialization",  
> > 
> > "strongly happens before" is genuine gibberish. Either something
> > happens before or it doesn't, the adverb is entirely superfluous.  
> 
> Terms are explicitly defined by the C++ standard precisely because
> their meaning cannot be inferred by using ordinary English to
> interpret the words that make them up. Both "happens before" and
> "strongly happens before" are separate pieces of C++ jargon, and the
> requirements for qualifying as "strongly happens before" are in fact
> stronger than those for "happens before".
> 
> "An evaluation A happens before an evaluation B (or, equivalently, B
> happens after A) if:
> (10.1)— A is sequenced before B, or
> (10.2)— A inter-thread happens before B.
> The implementation shall ensure that no program execution
> demonstrates a cycle in the “happens before” relation. [Note: This
> cycle would otherwise be possible only through the use of consume
> operations. — end note]" (6.9.2.1p10).
> 
> the first occurrence of "happens before" in that clause is in italics,
> an ISO convention indicating that it is a piece of specialized jargon
> whose definition is provided by the sentence in which it occurs. Note
> that "sequenced before" and "inter-thread happens before" are two
> other pieces of standard-defined jargon.
> 
> "An evaluation A strongly happens before an evaluation D if, either
> (12.1)— A is sequenced before D, or
> (12.2)— A synchronizes with D, and both A and D are sequentially
> consistent atomic operations (31.4), or
> (12.3)— there are evaluations B and C such that A is sequenced before
> B, B simply happens before C, and C is sequenced before D, or
> (12.4)— there is an evaluation B such that A strongly happens before
> B, and B strongly happens before D.
> [Note: Informally, if A strongly happens before B, then A appears to
> be evaluated before B in all contexts. Strongly happens before
> excludes consume operations. — end note]"
> 
> The first occurrence of "strongly happens before" in that clause is
> also italicized.
> 
> Note that "A is sequenced before D" would be sufficient to ensure that
> both "A happens before D" and "A strongly happens before D" are true.
> The difference between the two terms only shows up if A is not
> sequenced before D. In that case, at a minimum you must have "A
> inter-thread happens before D", but is not synchronized with D.
> 
> For instance A inter-thread happens before D if it is
> dependency-ordered before D. (6.9.2.1p9). This could happen if A
> performs a release operation on an atomic object M , and, in another
> thread, D performs a consume operation on M and reads the value
> written by A (6.9.2.1p8).
> 
> In that case, the requirements associated with "A happens before D"
> must be met, but those associated with "A strongly happens before D"
> need not be.
> 

You probably paid attentions that the text is not crystal clear.
It looks like authors of the Standard invent their own terminology not
only when absolutely necessary but sometimes even when there exist
established terms for the same things. To their defense, I could say
that in the branch of CS that is related to concurrency and parallelism
very few terms are 100% consensus.

> Do you need an explanation of the parts of the above explanation that
> use the terms "release" and "consume"? I have little experience with
> multi-threaded code - someone else might be able to explain those
> better than I can.
> 

I suspected that the difference between "strong happens before" and
"happens before" is somehow related to implied ordering due to
causality. After reading the text above my feeling changed from
suspicion to strong suspicion. But it is not yet a certainty.

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Thread

Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-03-30 08:57 +0000
  Re: Pre-main construction order in modules Richard Damon <richard@damon-family.org> - 2025-03-30 07:21 -0400
    Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 16:22 +0000
      Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-30 19:56 +0200
        Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 18:00 +0000
  Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-03-30 10:38 -0400
    Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-03-30 15:30 +0000
      Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 15:59 +0000
        Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-03-30 16:09 +0000
          Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 16:17 +0000
            Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-03-30 16:23 +0000
              Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 16:26 +0000
                Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-03-31 08:20 +0000
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-31 10:46 +0200
                Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-03-31 11:56 +0300
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-31 11:11 +0200
                Re: Pre-main construction order in modules Richard Damon <richard@damon-family.org> - 2025-03-31 07:25 -0400
                Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-03-31 15:26 +0300
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-31 14:32 +0200
                Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-03-31 15:44 +0300
                Re: Pre-main construction order in modules Jakob Bohm <egenagwemdimtapsar@jbohm.dk> - 2025-04-01 06:06 +0200
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-01 08:41 +0200
                Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-04-01 11:41 +0300
                Re: Pre-main construction order in modules Richard Damon <richard@damon-family.org> - 2025-03-31 07:22 -0400
              Re: Pre-main construction order in modules Richard Damon <richard@damon-family.org> - 2025-03-30 15:05 -0400
            Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-30 19:58 +0200
              Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 18:02 +0000
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-30 20:05 +0200
                Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 18:07 +0000
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-30 20:08 +0200
                Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 18:11 +0000
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-30 20:17 +0200
                Re: Pre-main construction order in modules Mr Flibble <flibble@reddwarf.jmc.corp> - 2025-03-30 18:20 +0000
                Re: Pre-main construction order in modules Richard Damon <richard@damon-family.org> - 2025-03-30 15:01 -0400
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-30 22:15 +0200
                Re: Pre-main construction order in modules "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-03-30 13:57 -0700
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-31 07:37 +0200
                Re: Pre-main construction order in modules "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-03-31 21:54 -0700
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-01 08:41 +0200
                Re: Pre-main construction order in modules "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-01 00:00 -0700
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-01 11:42 +0200
                Re: Pre-main construction order in modules "Fred. Zwarts" <F.Zwarts@HetNet.nl> - 2025-04-01 12:00 +0200
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-01 14:16 +0200
                Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-01 16:03 +0200
      Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-03-31 11:49 +0300
        Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-03-31 09:09 +0000
          Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-03-31 15:39 +0300
            Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-03-31 14:01 +0000
              Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-03-31 20:06 +0300
              Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-03-31 19:42 -0400
                Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-04-01 07:26 +0000
                Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-04-01 11:48 +0300
                Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-04-01 08:57 +0000
                Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-04-01 12:21 +0300
                Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-04-01 10:08 +0000
                Re: Pre-main construction order in modules Michael S <already5chosen@yahoo.com> - 2025-04-01 13:12 +0300
                Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-04-01 10:23 +0000
                Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-04-01 10:27 +0000
                Re: Pre-main construction order in modules Michael S <already5chosen@yahoo.com> - 2025-04-01 13:20 +0300
                Re: Pre-main construction order in modules Paavo Helde <eesnimi@osa.pri.ee> - 2025-04-01 13:33 +0300
                Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-04-01 10:48 +0000
                Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-04-01 14:37 -0400
                Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-04-01 14:37 -0400
                Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-04-01 14:32 -0400
                Re: Pre-main construction order in modules "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-01 12:39 -0700
                Re: Pre-main construction order in modules Michael S <already5chosen@yahoo.com> - 2025-04-01 23:26 +0300
                Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-04-01 19:08 -0400
                Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-04-01 22:55 -0400
                Re: Pre-main construction order in modules Muttley@DastardlyHQ.org - 2025-04-02 07:34 +0000
        Re: Pre-main construction order in modules scott@slp53.sl.home (Scott Lurndal) - 2025-03-31 14:15 +0000
          Re: Pre-main construction order in modules Bonita Montero <Bonita.Montero@gmail.com> - 2025-03-31 16:47 +0200
      Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-03-31 10:29 -0400
        Re: Pre-main construction order in modules Jakob Bohm <egenagwemdimtapsar@jbohm.dk> - 2025-04-01 06:29 +0200
          Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-04-01 13:55 -0400
            Re: Pre-main construction order in modules Michael S <already5chosen@yahoo.com> - 2025-04-01 23:10 +0300
              Re: Pre-main construction order in modules Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2025-04-01 14:20 -0700
              Re: Pre-main construction order in modules James Kuyper <jameskuyper@alumni.caltech.edu> - 2025-04-01 18:57 -0400
              Re: Pre-main construction order in modules David Brown <david.brown@hesbynett.no> - 2025-04-02 10:29 +0200

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