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Re: #include <stdint.h>

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On 10/6/21 6:14 PM, Branimir Maksimovic wrote:
> On 2021-10-06, James Kuyper <jameskuyper@alumni.caltech.edu> wrote:
...
>> In several locations, the standard says "The same representation and
>> alignment requirements are meant to imply interchangeability as
>> arguments to functions, return values from functions, and members of
>> unions."
>>
>> There's several problems with that statement. Firstly, "are meant to
>> imply" is weasel-wording. It could have said, more simply and
>> forcefully, "implies". Secondly, the implication doesn't hold up under
>> close examination. For instance, unsigned and signed arguments with the
>> same alignment and same representation for positive values of the signed
>> type could still be passed by different methods as arguments or return
>> values, which would prevent them from being interchangeable. Finally,
>> that wording only appears in informative footnotes, not in normative text.
>>
>> After raising this issue many times over a couple of decades, I finally
>> got confirmation from Larry Jones in 2011 (at that time, secretary of
>> the committee) that use of "are meant to imply" rather than "implies"
>> was deliberate, because it was in fact understood that no such
>> implication was correct. He also confirmed that the non-normative nature
>> of that text was also deliberate - the committee did NOT want to mandate
>> that the types be interchangeable, only to recommend that they be made
>> interchangeable.
> 
> Problem is that C does not defines exact type and representation.
> New language have noted that mistake so they have exact representation,
> even if that not corresponds to hardware.
> C goed in a way to have performance and portability, which of course
> you can't have both, you just have buggy programs :p

No, that's a distinct issue. If the C standard were changed to
explicitly specify the exact representation of every data type, and no
other changes were made, it would still be perfectly legal, for
instance, for an implementation to use different methods for passing
signed and unsigned arguments; on an implementation that did so, they
would not be interchangeable as arguments of or return values from
functions, not even for values that are representable in both types.

It's also not necessarily a problem with C. Different languages are
designed for different purposes. C was designed to be efficiently
implementable almost everywhere - at the cost of making it more
difficult to port code from one implementation to another. Other
languages consider it more important to be able to port code between any
two implementations of the language, at the cost of the language not
being efficiently implementable on all platforms.
C has added the size-named integer types, which mitigates this problem
somewhat.

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#include <stdint.h> SIMON <invalid@invalid.invalid> - 2021-06-13 23:08 +0100
  Re: #include <stdint.h> Bart <bc@freeuk.com> - 2021-06-13 23:27 +0100
    Re: #include <stdint.h> Bart <bc@freeuk.com> - 2021-06-13 23:57 +0100
      Re: #include <stdint.h> Philipp Klaus Krause <pkk@spth.de> - 2021-06-14 09:03 +0200
        Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-14 01:23 -0700
          Re: #include <stdint.h> Philipp Klaus Krause <pkk@spth.de> - 2021-06-14 12:31 +0200
        Re: #include <stdint.h> Bart <bc@freeuk.com> - 2021-06-14 11:54 +0100
  Re: #include <stdint.h> James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-06-13 18:34 -0400
  Re: #include <stdint.h> Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-06-13 23:34 +0100
  Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-13 17:48 -0700
    Re: #include <stdint.h> Philipp Klaus Krause <pkk@spth.de> - 2021-06-14 09:09 +0200
      Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-14 01:24 -0700
        Re: #include <stdint.h> Philipp Klaus Krause <pkk@spth.de> - 2021-06-14 12:30 +0200
    Re: #include <stdint.h> Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-06-24 10:31 -0700
      Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-24 11:28 -0700
        Re: #include <stdint.h> Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-11 02:49 -0700
          Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-07-11 15:30 -0700
            Re: #include <stdint.h> Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-16 03:33 -0700
              Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-07-16 12:31 -0700
                Re: #include <stdint.h> Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-09-30 07:07 -0700
                Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-30 08:42 -0700
                Re: #include <stdint.h> Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-06 03:55 -0700
                Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-06 07:06 -0700
                Re: #include <stdint.h> James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-06 11:47 -0400
        Re: #include <stdint.h> Andrey Tarasevich <andreytarasevich@hotmail.com> - 2021-10-06 09:35 -0700
          Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-06 10:06 -0700
          Re: #include <stdint.h> James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-06 17:40 -0400
            Re: #include <stdint.h> Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-06 22:14 +0000
              Re: #include <stdint.h> James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-06 20:06 -0400
                Re: #include <stdint.h> Branimir Maksimovic <branimir.maksimovic@icloud.com> - 2021-10-07 02:15 +0000
      Re: #include <stdint.h> Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-06-24 22:34 +0100
        Re: #include <stdint.h> Öö Tiib <ootiib@hot.ee> - 2021-06-24 15:01 -0700
          Re: #include <stdint.h> Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-24 15:26 -0700
        Re: #include <stdint.h> Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-11 02:14 -0700

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