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Re: bit-fields of type unsigned long and unsigned long long

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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>
>> Philipp Klaus Krause <pkk@spth.de> writes:
>>
>>> Am 23.06.21 um 19:53 schrieb Tim Rentsch:
>>>
>>>> Bit-fields of types signed and unsigned may use widths up to the
>>>> widths of intmax_t and uintmax_t, respectively.
>>>
>>> WG14 usually doesn't like to use the same syntax as C++ but with a
>>> different meaning.
>>> AFAIK, in C++, you can have an int bit-field wider than int (or whatever
>>> else the type is), but the upper bits then are padding bits.
>>
>> The obvious answer is to ask the C++ committee to change their
>> silly rule.  And if they don't want to change it, just ignore it;
>> the C++ rule is already incompatible with C, now it will just be
>> incompatible in a different way.  The gap between C and C++ has
>> increased to the point where they should be treated as separate
>> and independent languages.
>
> It's no more incompatible than any other C++ feature that doesn't exist
> in C.  A program that defines a bit field with a length that exceeds the
> width of the type is a constraint violation in C, and valid in C++.

I don't know what point you're trying to make here.  How it works
in C++ is different from how it works in C.  That the C standard
deems it a constraint violation to me seems irrelevant.  The
important point is that the behaviors in the two cases aren't
the same.

> On the other hand, I agree that the C++ rule *seems* silly.  I wonder
> what the rationale is.  (The earliest reference to the rule that I found
> is in the C++ 1998 standard.)
>
> It would be nice to avoid *gratuitous* incompatibilities between C and
> C++.

It would be even nicer in this particular case if C++ changed
its silly rule to the rule I suggested for C.

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Thread

bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-22 16:49 +0200
  Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-22 17:18 +0200
    Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-22 11:17 -0700
      Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-23 08:25 +0200
        Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-23 08:59 +0200
          Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-23 13:12 +0200
            Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-23 14:14 +0200
              Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-23 17:45 +0200
                Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-23 10:22 -0700
                Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-23 19:52 +0200
                Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-23 16:12 -0700
                Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-24 10:41 +0200
                Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-24 10:32 +0200
        Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-23 00:39 -0700
  Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-23 13:22 +0200
    Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-23 18:27 +0200
  Re: bit-fields of type unsigned long and unsigned long long Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-06-23 10:53 -0700
    Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-23 20:13 +0200
      Re: bit-fields of type unsigned long and unsigned long long Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-06-24 11:48 -0700
        Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-24 12:23 -0700
          Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-24 22:40 +0200
          Re: bit-fields of type unsigned long and unsigned long long Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-10 09:13 -0700
        Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-24 22:14 +0200
          Re: bit-fields of type unsigned long and unsigned long long Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-10 09:23 -0700
    Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-24 11:02 +0200
      Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-24 11:06 -0700
        Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-24 23:11 +0200
          Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-24 15:16 -0700
            Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-25 10:43 +0200
              Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-25 02:02 -0700
                Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-25 13:54 +0200
                Re: bit-fields of type unsigned long and unsigned long long Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-06-25 13:07 +0100
                Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-25 15:17 +0200
                Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-25 08:22 -0700
                Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-25 18:22 +0200
                Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-25 13:28 -0700
                Re: bit-fields of type unsigned long and unsigned long long Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-06-25 19:12 +0100
                Re: bit-fields of type unsigned long and unsigned long long Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-07-10 08:58 -0700
                Re: bit-fields of type unsigned long and unsigned long long Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-06-25 08:09 -0700
              Re: bit-fields of type unsigned long and unsigned long long Philipp Klaus Krause <pkk@spth.de> - 2021-06-25 14:43 +0200
                Re: bit-fields of type unsigned long and unsigned long long David Brown <david.brown@hesbynett.no> - 2021-06-25 15:33 +0200
                Re: bit-fields of type unsigned long and unsigned long long Jakob Bohm <jb-usenet@wisemo.com.invalid> - 2021-07-06 23:18 +0200

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