Re: "C++: Size Matters in Platform Compatibility"

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.lang.c++, comp.lang.c
Subject	Re: "C++: Size Matters in Platform Compatibility"
Date	2019-08-18 12:32 +0200
Organization	A noiseless patient Spider
Message-ID	<qjb9fj$mis$1@dont-email.me> (permalink)
References	<qj6ung$map$1@dont-email.me> <qj8u95$3if$1@dont-email.me> <mnkglelt8koldbugfin9q27eb3qptod8b5@4ax.com>

Cross-posted to 2 groups.

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On 17/08/2019 21:43, Geoff wrote:
> On Sat, 17 Aug 2019 15:08:52 +0200, David Brown
> <david.brown@hesbynett.no> wrote:
> 
> [snip]
> 
>>
>> If you are storing data in binary formats that need to be portable, you
>> need to define and document the format, making it independent of the
>> platform.  The author here glosses over the important bits - endianness
>> and alignment (and consequently padding), which he doesn't mention at all.
>>
> 
> He does mention endianess and he declined to discuss it, saying it
> needs a separate discussion. You are the second poster here to
> overlook that.

I said he glossed over it, which he did.  I did not say he ignored it 
completely - he said it was an issue but did not discuss it further.

> 
> [snip]
> 
>> Often the most sensible formats
>> is 64 bit Unix epoch timestamps (happily covering the big bang up to
>> well past the death of our sun).  IEEE floating point double Unix epoch
>> seconds will last longer than protons, and give you accurate fractions
>> of a second for more normal timeframes.  If these are not suitable,
>> define a format for your particular requirements.
> 
> The UNIX epoch-based 64-bit time is good only if you believe the sun
> will only last another 2.147 billion years.

292 billion years, by my counting.  By that time, any issues with 
rollover will be an SEP¹.

> The epoch time rolls over
> in the year 2,147,485,547 on MacOS. The sun is calculated to have
> another 5.4 billion years of hydrogen fuel left.

That sounds like a signed 32-bit integer storing the number of years 
(not an unreasonable choice for a split time/date format).

> 
> Proton decay, so far, is only theoretical. It has never been observed.

True.  And perhaps humankind will have moved to a different, newer 
universe by that time.  We /could/ standardise on 128-bit second 
timestamps, but I think it is important to leave a few challenges to 
keep future generations motivated :-)

> 
> [snip]
> 

¹ <https://en.wikipedia.org/wiki/Somebody_else%27s_problem>

Thread

"C++: Size Matters in Platform Compatibility" Lynn McGuire <lynnmcguire5@gmail.com> - 2019-08-16 14:04 -0500
  Re: "C++: Size Matters in Platform Compatibility" Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-08-16 20:45 +0000
  Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-17 15:08 +0200
    Re: "C++: Size Matters in Platform Compatibility" Geoff <geoff@invalid.invalid> - 2019-08-17 12:43 -0700
      Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-18 12:32 +0200
        Re: "C++: Size Matters in Platform Compatibility" Geoff <geoff@invalid.invalid> - 2019-08-18 13:10 -0700
          Re: "C++: Size Matters in Platform Compatibility" Bart <bc@freeuk.com> - 2019-08-18 21:15 +0100
          Re: "C++: Size Matters in Platform Compatibility" Keith Thompson <kst-u@mib.org> - 2019-08-18 14:49 -0700
            Re: "C++: Size Matters in Platform Compatibility" Keith Thompson <kst-u@mib.org> - 2019-08-18 14:51 -0700
          Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-19 08:43 +0200
            Re: "C++: Size Matters in Platform Compatibility" "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-08-19 09:15 +0200
            Re: "C++: Size Matters in Platform Compatibility" Öö Tiib <ootiib@hot.ee> - 2019-08-19 01:07 -0700
      Re: "C++: Size Matters in Platform Compatibility" Bonita Montero <Bonita.Montero@gmail.com> - 2019-08-21 17:14 +0200
        Re: "C++: Size Matters in Platform Compatibility" Eli the Bearded <*@eli.users.panix.com> - 2019-08-21 18:30 +0000
          Re: "C++: Size Matters in Platform Compatibility" scott@slp53.sl.home (Scott Lurndal) - 2019-08-21 19:05 +0000
          Re: "C++: Size Matters in Platform Compatibility" Bonita Montero <Bonita.Montero@gmail.com> - 2019-08-21 21:25 +0200
          Re: "C++: Size Matters in Platform Compatibility" Keith Thompson <kst-u@mib.org> - 2019-08-21 12:28 -0700
          Re: "C++: Size Matters in Platform Compatibility" Richard Damon <Richard@Damon-Family.org> - 2019-08-22 22:58 -0400
            Re: "C++: Size Matters in Platform Compatibility" Eli the Bearded <*@eli.users.panix.com> - 2019-08-23 19:15 +0000
    Re: "C++: Size Matters in Platform Compatibility" Anton Shepelev <anton.txt@gmail.com> - 2019-08-18 15:59 +0300
      Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-18 16:32 +0200
    Re: "C++: Size Matters in Platform Compatibility" Juha Nieminen <nospam@thanks.invalid> - 2019-08-19 07:29 +0000
      Re: "C++: Size Matters in Platform Compatibility" Paavo Helde <myfirstname@osa.pri.ee> - 2019-08-19 12:20 +0300
      Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-19 11:22 +0200
        Re: "C++: Size Matters in Platform Compatibility" Richard Damon <Richard@Damon-Family.org> - 2019-08-23 14:14 -0400
          Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-24 20:56 +0200
            Re: "C++: Size Matters in Platform Compatibility" Robert Wessel <robertwessel2@yahoo.com> - 2019-08-24 23:43 -0500
              Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-25 12:11 +0200
                Re: "C++: Size Matters in Platform Compatibility" Richard Damon <Richard@Damon-Family.org> - 2019-08-25 07:33 -0700
                Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-25 20:27 +0200
                Re: "C++: Size Matters in Platform Compatibility" Robert Wessel <robertwessel2@yahoo.com> - 2019-08-25 10:22 -0500
    Re: "C++: Size Matters in Platform Compatibility" Lynn McGuire <lynnmcguire5@gmail.com> - 2019-08-19 15:05 -0500
      Re: "C++: Size Matters in Platform Compatibility" scott@slp53.sl.home (Scott Lurndal) - 2019-08-19 20:17 +0000
        Re: "C++: Size Matters in Platform Compatibility" David Brown <david.brown@hesbynett.no> - 2019-08-20 08:21 +0200
          Re: "C++: Size Matters in Platform Compatibility" Lynn McGuire <lynnmcguire5@gmail.com> - 2019-08-20 14:38 -0500
      Re: "C++: Size Matters in Platform Compatibility" James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-08-21 09:15 -0400
  Re: "C++: Size Matters in Platform Compatibility" Anton Shepelev <anton.txt@gmail.com> - 2019-08-18 15:20 +0300
    Re: "C++: Size Matters in Platform Compatibility" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-08-18 14:50 +0100

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