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Re: why use static_cast ?

From Juha Nieminen <nospam@thanks.invalid>
Newsgroups comp.lang.c++
Subject Re: why use static_cast ?
Date 2022-10-20 07:19 +0000
Organization Aioe.org NNTP Server
Message-ID <tiqsp8$1ojk$1@gioia.aioe.org> (permalink)
References <tiqa5e$8aju$1@dont-email.me> <035d8c85-23d2-451b-a387-855b369b4c12n@googlegroups.com> <tiqls3$1e6b$1@gioia.aioe.org> <tiqpdl$9c3p$1@dont-email.me>

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Andrey Tarasevich <andreytarasevich@hotmail.com> wrote:
> On 10/19/2022 10:21 PM, Lynn McGuire wrote:
>> 
>> Why ?  They are both pointers to 8 byte objects.  I am just declaring 
>> that I want to use the same address as a 8 byte character string (no 
>> null !) or a long long integer.
>> 
> 
> You can't, neither in C nor in C++. An object (lvalue) of type `T` can 
> only be accessed as an object (lvalue) of type `T` (with few 
> exceptions). This is well known as the "strict aliasing" rule.

AFAIK any value of any type can always be safely read with an (unsigned)
char pointer (as long as you remain within the limits of the type size).

If if weren't, it would be impossible to eg. create your own version
of memcmp().

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Thread

why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-19 21:01 -0500
  Re: why use static_cast ? "daniel...@gmail.com" <danielaparker@gmail.com> - 2022-10-19 19:40 -0700
    Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-20 00:21 -0500
      Re: why use static_cast ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-10-19 23:21 -0700
        Re: why use static_cast ? Juha Nieminen <nospam@thanks.invalid> - 2022-10-20 07:19 +0000
          Re: why use static_cast ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-10-20 00:21 -0700
      Re: why use static_cast ? Paul N <gw7rib@aol.com> - 2022-10-20 04:23 -0700
        Re: why use static_cast ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-10-20 14:14 +0100
        Re: why use static_cast ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-10-20 09:17 -0700
          Re: why use static_cast ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-10-20 09:52 -0700
            Re: why use static_cast ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-15 17:10 -0800
              Re: why use static_cast ? Juha Nieminen <nospam@thanks.invalid> - 2022-11-16 09:26 +0000
                Re: why use static_cast ? David Brown <david.brown@hesbynett.no> - 2022-11-16 14:36 +0100
                Re: why use static_cast ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-20 05:54 -0800
      Re: why use static_cast ? "daniel...@gmail.com" <danielaparker@gmail.com> - 2022-10-20 08:11 -0700
  Re: why use static_cast ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-10-19 20:09 -0700
  Re: why use static_cast ? Juha Nieminen <nospam@thanks.invalid> - 2022-10-20 05:44 +0000
    Re: why use static_cast ? Gawr Gura <gawrgura@mail.hololive.com> - 2022-10-20 14:50 +0000
      Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-20 17:53 +0300
  Re: why use static_cast ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-10-20 08:52 +0200
    Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-20 17:52 +0300
  Re: why use static_cast ? scott@slp53.sl.home (Scott Lurndal) - 2022-10-20 13:55 +0000
    Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-20 17:55 +0300
      Re: why use static_cast ? scott@slp53.sl.home (Scott Lurndal) - 2022-10-20 15:01 +0000
        Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-20 18:32 +0300
          Re: why use static_cast ? scott@slp53.sl.home (Scott Lurndal) - 2022-10-20 16:07 +0000
            Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-20 20:14 +0300
              Re: why use static_cast ? scott@slp53.sl.home (Scott Lurndal) - 2022-10-20 17:30 +0000
                Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-20 20:41 +0300
              Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-21 14:05 -0500
                Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-22 00:09 +0300
                Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-22 08:47 +0300
                Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-22 15:03 -0500
                Re: why use static_cast ? Muttley@dastardlyhq.com - 2022-10-23 07:35 +0000
                Re: why use static_cast ? JiiPee <kerrttuPoistaTama11@gmail.com> - 2022-10-23 15:28 +0300
                Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-23 14:13 -0500
                Re: why use static_cast ? Manfred <noname@add.invalid> - 2022-10-23 20:27 +0200
                Re: why use static_cast ? Michael S <already5chosen@yahoo.com> - 2022-10-23 15:04 -0700
                Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-23 23:14 -0500
          Re: why use static_cast ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-10-21 17:21 +0200
      Re: why use static_cast ? Bonita Montero <Bonita.Montero@gmail.com> - 2022-10-21 17:24 +0200
    Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-20 13:21 -0500
      Re: why use static_cast ? Manfred <noname@add.invalid> - 2022-10-21 05:52 +0200
        Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-21 13:59 -0500
          Re: why use static_cast ? Bo Persson <bo@bo-persson.se> - 2022-10-22 18:31 +0200
            Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-22 15:05 -0500
            Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-22 17:34 -0500
        Re: why use static_cast ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-02 17:54 -0700
          Re: why use static_cast ? Öö Tiib <ootiib@hot.ee> - 2022-11-03 08:51 -0700
            Re: why use static_cast ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-15 16:19 -0800
              Re: why use static_cast ? Öö Tiib <ootiib@hot.ee> - 2022-11-15 23:02 -0800
                Re: why use static_cast ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-20 05:59 -0800
                Re: why use static_cast ? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-11-20 15:05 +0100
                Re: why use static_cast ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-20 07:22 -0800
                Re: why use static_cast ? Öö Tiib <ootiib@hot.ee> - 2022-11-20 08:40 -0800
                Re: why use static_cast ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-28 20:43 -0800
    Re: why use static_cast ? Juha Nieminen <nospam@thanks.invalid> - 2022-11-04 07:27 +0000
      Re: why use static_cast ? scott@slp53.sl.home (Scott Lurndal) - 2022-11-04 13:47 +0000
        Re: why use static_cast ? Vir Campestris <vir.campestris@invalid.invalid> - 2022-11-05 21:34 +0000
        Re: why use static_cast ? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-11-06 03:25 -0500
        Re: why use static_cast ? Paavo Helde <eesnimi@osa.pri.ee> - 2022-11-06 17:34 +0200
          Re: why use static_cast ? Juha Nieminen <nospam@thanks.invalid> - 2022-11-07 07:13 +0000
      Re: why use static_cast ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-11-04 09:09 -0700
  Re: why use static_cast ? Lynn McGuire <lynnmcguire5@gmail.com> - 2022-10-20 13:21 -0500

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