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Re: Function pointer size (was Re: nullptr is not 0)

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On 5/17/2022 1:30 PM, Vir Campestris wrote:
> On 09/05/2022 22:56, Scott Lurndal wrote:
>> Vir Campestris <vir.campestris@invalid.invalid> writes:
>>> On 09/05/2022 06:06, Juha Nieminen wrote:
>>>> Member function pointers shouldn't really be thought of as normal 
>>>> pointers.
>>>> They are rather different beasts, behave differently in many 
>>>> respects, and
>>>> you can't even convert from member-function-pointer to 
>>>> regular-pointer and
>>>> back safely because they are completely incompatible with each other.
>>>> They are likely not even the same size.
>>>
>>> _Likely_ not even the same size?
>>
>> With g++ on linux, sizeof(member function pointer) returns
>> 16 bytes.
>>
> 
> :O
> 
> I just experimented. Yes, it's 16 bytes, while an ordinary function 
> pointer is only 8 (Linux 64, g++).
> 
> But the top 8 bytes always seem to be zero.
> 
> When are they anything else? Because if they aren't there's no reason 
> for the different size.

Iirc, even if nullptr is defined to be something like 0xDEADBEEF, it 
will still work when compared to 0. So:

void* p0 = nullptr;
void* p1 = 0;

p0 == p1

and (p0 == 0 && p1 == 0) is true.

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nullptr is not 0 Sam <sam@email-scan.com> - 2022-05-08 09:45 -0400
  Re: nullptr is not 0 "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-08 16:21 +0200
  Re: nullptr is not 0 Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-08 10:00 -0700
  Re: nullptr is not 0 Bonita Montero <Bonita.Montero@gmail.com> - 2022-05-09 06:38 +0200
  Re: nullptr is not 0 Juha Nieminen <nospam@thanks.invalid> - 2022-05-09 05:06 +0000
    Re: nullptr is not 0 Vir Campestris <vir.campestris@invalid.invalid> - 2022-05-09 21:46 +0100
      Re: nullptr is not 0 Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-09 13:57 -0700
        Re: nullptr is not 0 Juha Nieminen <nospam@thanks.invalid> - 2022-05-10 05:04 +0000
          Re: nullptr is not 0 Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-09 22:33 -0700
      Re: nullptr is not 0 scott@slp53.sl.home (Scott Lurndal) - 2022-05-09 21:56 +0000
        Function pointer size (was Re: nullptr is not 0) Vir Campestris <vir.campestris@invalid.invalid> - 2022-05-17 21:30 +0100
          Re: Function pointer size (was Re: nullptr is not 0) scott@slp53.sl.home (Scott Lurndal) - 2022-05-17 21:00 +0000
            Re: Function pointer size (was Re: nullptr is not 0) Vir Campestris <vir.campestris@invalid.invalid> - 2022-05-19 21:52 +0100
            Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-19 14:08 -0700
          Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-17 17:05 -0700
          Re: Function pointer size (was Re: nullptr is not 0) Juha Nieminen <nospam@thanks.invalid> - 2022-05-18 04:46 +0000
            Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-18 02:14 -0700
              Re: Function pointer size (was Re: nullptr is not 0) Juha Nieminen <nospam@thanks.invalid> - 2022-05-19 14:53 +0000
                Re: Function pointer size (was Re: nullptr is not 0) "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-05-19 17:19 +0200
                Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-19 10:14 -0700
                Re: Function pointer size (was Re: nullptr is not 0) Richard Damon <Richard@Damon-Family.org> - 2022-05-19 13:45 -0400
                Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-19 11:31 -0700
                Re: Function pointer size (was Re: nullptr is not 0) Juha Nieminen <nospam@thanks.invalid> - 2022-05-20 06:58 +0000
                Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-20 00:11 -0700
                Re: Function pointer size (was Re: nullptr is not 0) Richard Damon <Richard@Damon-Family.org> - 2022-05-19 12:27 -0400
                Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-19 09:47 -0700
                Re: Function pointer size (was Re: nullptr is not 0) Richard Damon <Richard@Damon-Family.org> - 2022-05-19 13:36 -0400
                Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-19 11:24 -0700
                Re: Function pointer size (was Re: nullptr is not 0) Richard Damon <Richard@Damon-Family.org> - 2022-05-19 21:32 -0400
                Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-19 20:28 -0700
                Re: Function pointer size (was Re: nullptr is not 0) Richard Damon <Richard@Damon-Family.org> - 2022-05-20 10:57 -0400
                Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-19 09:35 -0700
                Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-19 10:10 -0700
                Re: Function pointer size (was Re: nullptr is not 0) Juha Nieminen <nospam@thanks.invalid> - 2022-05-20 07:15 +0000
          Re: Function pointer size (was Re: nullptr is not 0) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-05-18 11:50 -0700
            Re: Function pointer size (was Re: nullptr is not 0) Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-05-18 15:46 -0700
              Re: Function pointer size (was Re: nullptr is not 0) "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2022-05-19 20:52 -0700

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