Re: initializer list type deduction rules

From	Juha Nieminen <nospam@thanks.invalid>
Newsgroups	comp.lang.c++
Subject	Re: initializer list type deduction rules
Date	2022-08-10 02:34 +0000
Organization	Aioe.org NNTP Server
Message-ID	<tcv5fs$12np$2@gioia.aioe.org> (permalink)
References	<tct3rm$1l9a$1@gioia.aioe.org> <tcupcj$1gpp3$1@dont-email.me>

Show all headers | View raw

Andrey Tarasevich <andreytarasevich@hotmail.com> wrote:
> On 8/9/2022 12:54 AM, Juha Nieminen wrote:
>> Even in such a simple case as this:
>> 
>>    unsigned values[] = { 1, 2, 3, 5 10 };
>> 
>> vs. this:
>> 
>>    for(unsigned value: { 1, 2, 3, 5, 10 })
>> 
>> if you turn on enough compiler warnings eg. gcc will warn about the
>> second one (converting 'int' to 'unsigned' may change the sign of the
>> result) but not the first one. I believe that in the first case the
>> compiler deduces the type of the initializer list to be 'unsigned'
>> (even though the literals themselves are of type 'int'), while in
>> the second case it does not.
> 
> There's no point in searching for any hidden logic in this or trying to 
> guess the reason. The message you describe is not a standard diagnostic 
> message, i.e. it is not in any way mandated by the standard. Both 
> examples are perfectly valid as is. No diagnostic of any kind is expected.
> 
> The two contexts are significantly different semantically, which means 
> that they are likely handled by two different parts of the compiler. The 
> message is just a whim of some developer, who inserted that message in 
> one context and didn't bother to do something similar to the other context.

You are missing my point.

The point is not the warning itself. The point is that the warning
demonstrates that in the former case the values are treated as unsigned
ints, while in the second case they are treated as signed ints (even
though the variable is of type unsigned).

Back to comp.lang.c++ | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-09 07:54 +0000
  Re: initializer list type deduction rules Bo Persson <bo@bo-persson.se> - 2022-08-09 10:43 +0200
  Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-09 09:00 -0700
    Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-09 16:06 +0000
      Re: initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-10 02:32 +0000
        Re: initializer list type deduction rules Paavo Helde <eesnimi@osa.pri.ee> - 2022-08-10 09:11 +0300
          Re: initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-10 06:57 +0000
        Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-10 07:31 +0000
      Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-10 00:40 -0700
        Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-10 07:55 +0000
          Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-10 01:13 -0700
            Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-10 08:21 +0000
              Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-10 11:13 -0700
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-12 08:26 +0000
                Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-12 03:38 -0700
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-12 10:48 +0000
                Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-12 04:54 -0700
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-12 14:34 +0000
                Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-12 08:34 -0700
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-12 15:57 +0000
                Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-12 09:16 -0700
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-13 09:35 +0000
                Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-13 09:44 -0700
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-14 11:12 +0000
                Re: initializer list type deduction rules scott@slp53.sl.home (Scott Lurndal) - 2022-08-12 14:58 +0000
                Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-12 08:59 -0700
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-12 16:11 +0000
                Re: initializer list type deduction rules scott@slp53.sl.home (Scott Lurndal) - 2022-08-12 16:44 +0000
                Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-12 12:08 -0700
                Re: initializer list type deduction rules scott@slp53.sl.home (Scott Lurndal) - 2022-08-12 19:58 +0000
                Re: initializer list type deduction rules Öö Tiib <ootiib@hot.ee> - 2022-08-12 16:42 -0700
                Re: initializer list type deduction rules David Brown <david.brown@hesbynett.no> - 2022-08-13 18:14 +0200
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-14 11:06 +0000
                Re: initializer list type deduction rules David Brown <david.brown@hesbynett.no> - 2022-08-15 11:34 +0200
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-15 19:03 +0000
                Re: initializer list type deduction rules David Brown <david.brown@hesbynett.no> - 2022-08-15 21:23 +0200
                Re: initializer list type deduction rules red floyd <no.spam.here@its.invalid> - 2022-08-15 13:51 -0700
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-16 19:16 +0000
                Re: initializer list type deduction rules Paavo Helde <eesnimi@osa.pri.ee> - 2022-08-21 22:23 +0300
                Re: initializer list type deduction rules David Brown <david.brown@hesbynett.no> - 2022-08-22 08:08 +0200
                Re: initializer list type deduction rules Paavo Helde <eesnimi@osa.pri.ee> - 2022-08-22 11:37 +0300
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-22 10:23 +0000
          Re: initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-11 06:24 +0000
            Re: initializer list type deduction rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-08-11 16:37 +0100
              Re: initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-11 20:12 +0000
                Re: initializer list type deduction rules Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-08-12 00:09 +0100
                Re: initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-12 11:51 +0000
            Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-12 08:29 +0000
              Re: initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-12 12:08 +0000
                Re: initializer list type deduction rules Muttley@dastardlyhq.com - 2022-08-12 14:37 +0000
                Re: initializer list type deduction rules scott@slp53.sl.home (Scott Lurndal) - 2022-08-12 15:01 +0000
                Re: initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-15 06:04 +0000
  Re: initializer list type deduction rules Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-08-09 16:08 -0700
    Re: initializer list type deduction rules Juha Nieminen <nospam@thanks.invalid> - 2022-08-10 02:34 +0000

csiph-web