Re: How to write wide char string literals?

From	James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups	comp.lang.c++
Subject	Re: How to write wide char string literals?
Date	2021-07-02 16:15 -0400
Organization	A noiseless patient Spider
Message-ID	<sbns4s$cfd$1@dont-email.me> (permalink)
References	(4 earlier) <sbjh2o$1bq6$1@gioia.aioe.org> <sbkl6u$cd5$1@dont-email.me> <sbm82o$1rhp$1@gioia.aioe.org> <sbm94h$fif$1@dont-email.me> <sbmul5$1vu5$1@gioia.aioe.org>

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On 7/2/21 7:52 AM, Juha Nieminen wrote:
> James Kuyper <jameskuyper@alumni.caltech.edu> wrote:
>> so you should be able to freely use u prefixed
>> string literals and char16_t with code that needs to be portable to
>> Windows, but can also be used on other platforms.
> 
> But doesn't that have the exact same problem as in my original post?
No, because the original post used wchar_t and the L prefix, for which
the relevant encoding is implementation-defined. That's not the case for
char and the u8 prefix, char16_t and the u prefix, or for char32_t and
the U prefix.

I have a feeling that there's a misunderstanding somewhere in this
conversation, but I'm not sure yet what it is.

> In other words, in code like this:
> 
>     const char16_t *str = u"something";
> 
> the stuff between the quotation marks in the source code will use
> whatever encoding (ostensibly but not assuredly UTF-8), which the

I don't understand why you think that the source code encoding matters.
The only thing that matters is what characters are encoded. As long as
those encodings are for the characters {'u', '""', '\\', 'x', 'C', '2',
'\\', 'x', 'A', '9', '"'}, any fully conforming implementation must give
you the standard defined behavior for u"\xC2\xA9".

> compiler needs to convert to UTF-16 at compile time for writing
> it to the output binary.

When using the u8 prefix, UTF-8 encoding is guaranteed, for which every
codepoint from U+0000 to U+007F is represented by a single character
with a numerical value matching the code point.

When using the u prefix, UTF-16 encoding is guaranteed, for which every
codepoint from U+0000 to U+D7FF, and from U+E000 to U+FFFF, is
represented by a single character with a numerical value matching the
codepoint.

When using the U prefix, UTF-32 encoding is guaranteed, for which every
codepoint from U+0000 to U+D7FF, and from U+E000 to U+10FFFF, is
represented by a single character with a numerical value matching the
codepoint.

Since the meanings of the octal and hexadecimal escape sequences are
defined in terms of the numerical values of the corresponding
characters, if you use any of those prefixes, specifying the value of a
character within the specified range by using an octal or hexadecimal
escape sequence is precisely as portable as using the UCN with the same
numerical value. Using UCNs would be better because they are less
restricted, working just as well with the L prefix and with no prefix.
However, within those ranges, octal and hexadecimal escapes will work
just as well.

Do you know of any implementation of C++ that claims to be fully
conforming, for which that is not the case? If so, how do they justify
that claim?

'\xC2' and '\xA9' are in the ranges for the u and U prefixes. They would
not be in the range for the u8 prefix, but since the context was wide
characters, the u8 prefix is not relevant.

> Or is it guaranteed that the characters between u" and " will
> always be interpreted as UTF-8?

Source code characters between the u" and the " will be interpreted
according to an implementation-defined character encoding. But so long
as they encode {'\\', 'x', 'C', '2', '\\', 'x', 'A', '9'}, you should
get the standard-defined behavior for u"\xC2\xA9".

Thread

How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-06-30 07:57 +0000
  Re: How to write wide char string literals? Kli-Kla-Klawitter <kliklaklawitter69@gmail.com> - 2021-06-30 10:05 +0200
    Re: How to write wide char string literals? Ralf Goertz <me@myprovider.invalid> - 2021-06-30 10:30 +0200
      Re: How to write wide char string literals? Kli-Kla-Klawitter <kliklaklawitter69@gmail.com> - 2021-06-30 12:37 +0200
        Re: How to write wide char string literals? Ralf Goertz <me@myprovider.invalid> - 2021-07-01 09:19 +0200
          Re: How to write wide char string literals? Kli-Kla-Klawitter <kliklaklawitter69@gmail.com> - 2021-07-01 11:10 +0200
            Re: How to write wide char string literals? Ralf Goertz <me@myprovider.invalid> - 2021-07-01 11:36 +0200
              Re: How to write wide char string literals? Kli-Kla-Klawitter <kliklaklawitter69@gmail.com> - 2021-07-01 16:17 +0200
                Re: How to write wide char string literals? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-07-01 10:13 -0700
                Re: How to write wide char string literals? Kli-Kla-Klawitter <kliklaklawitter69@gmail.com> - 2021-07-01 19:27 +0200
                Re: How to write wide char string literals? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-07-01 11:21 -0700
                Re: How to write wide char string literals? Real Troll <real.troll@trolls.com> - 2021-07-01 18:45 +0000
                Re: How to write wide char string literals? Kli-Kla-Klawitter <kliklaklawitter69@gmail.com> - 2021-07-02 10:03 +0200
              Re: How to write wide char string literals? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-07-02 02:31 -0700
                Re: How to write wide char string literals? MrSpud_oyCn@92wvlb1hltq4dhc.gov.uk - 2021-07-02 09:38 +0000
                Re: How to write wide char string literals? Paavo Helde <myfirstname@osa.pri.ee> - 2021-07-02 13:52 +0300
                Re: How to write wide char string literals? MrSpud_zg8yg@nx8574z6ey2rc0y563k5i2.net - 2021-07-02 12:53 +0000
                Re: How to write wide char string literals? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-07-02 15:22 +0200
                Re: How to write wide char string literals? Paavo Helde <myfirstname@osa.pri.ee> - 2021-07-02 17:32 +0300
  Re: How to write wide char string literals? Ralf Goertz <me@myprovider.invalid> - 2021-06-30 10:08 +0200
  Re: How to write wide char string literals? MrSpud_r5j@ywn9entw2s.org - 2021-06-30 08:39 +0000
    Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-06-30 10:52 +0000
      Re: How to write wide char string literals? MrSpud_3u59h8@0c9tv3nddl090w2ynhm.gov - 2021-06-30 11:28 +0000
        Re: How to write wide char string literals? David Brown <david.brown@hesbynett.no> - 2021-06-30 14:01 +0200
  Re: How to write wide char string literals? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-06-30 10:55 +0200
    Re: How to write wide char string literals? David Brown <david.brown@hesbynett.no> - 2021-06-30 11:23 +0200
  Re: How to write wide char string literals? Richard Damon <Richard@Damon-Family.org> - 2021-06-30 06:51 -0400
    Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-06-30 11:09 +0000
      Re: How to write wide char string literals? Richard Damon <Richard@Damon-Family.org> - 2021-06-30 07:35 -0400
  Re: How to write wide char string literals? Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-30 14:03 +0300
    Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-06-30 11:13 +0000
      Re: How to write wide char string literals? Richard Damon <Richard@Damon-Family.org> - 2021-06-30 07:39 -0400
        Re: How to write wide char string literals? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-06-30 13:50 +0200
          Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-06-30 14:19 -0400
            Re: How to write wide char string literals? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-07-01 13:31 +0200
        Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-01 04:42 +0000
          Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-01 10:58 -0400
            Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-02 05:26 +0000
              Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-02 01:44 -0400
                Re: How to write wide char string literals? Bo Persson <bo@bo-persson.se> - 2021-07-02 08:33 +0200
                Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-02 11:52 +0000
                Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-02 16:15 -0400
                Re: How to write wide char string literals? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-07-03 03:30 +0200
                Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-03 00:44 -0400
                Re: How to write wide char string literals? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-07-03 13:31 +0200
                Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-03 08:44 -0400
                Re: How to write wide char string literals? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-07-03 16:28 +0200
                Re: How to write wide char string literals? Richard Damon <Richard@Damon-Family.org> - 2021-07-03 11:48 -0400
                Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-08 15:56 -0400
                Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-03 16:59 +0000
                Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-03 17:49 -0400
                Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-08 08:11 +0000
                Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-08 05:52 -0400
                Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-03 06:59 +0000
                Re: How to write wide char string literals? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-07-03 09:03 -0400
                Re: How to write wide char string literals? Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2021-07-03 14:23 +0100
                Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-03 17:06 +0000
                Re: How to write wide char string literals? Richard Damon <Richard@Damon-Family.org> - 2021-07-03 14:06 -0400
                Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-08 08:13 +0000
                Re: How to write wide char string literals? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2021-07-02 15:37 +0200
      Re: How to write wide char string literals? Manfred <noname@add.invalid> - 2021-06-30 16:54 +0200
      Re: How to write wide char string literals? Paavo Helde <myfirstname@osa.pri.ee> - 2021-06-30 17:56 +0300
  Re: How to write wide char string literals? Öö Tiib <ootiib@hot.ee> - 2021-06-30 09:22 -0700
  Re: How to write wide char string literals? Christian Gollwitzer <auriocus@gmx.de> - 2021-07-01 07:19 +0200
    Re: How to write wide char string literals? David Brown <david.brown@hesbynett.no> - 2021-07-01 10:29 +0200
      Re: How to write wide char string literals? Juha Nieminen <nospam@thanks.invalid> - 2021-07-01 08:44 +0000
        Re: How to write wide char string literals? David Brown <david.brown@hesbynett.no> - 2021-07-01 12:58 +0200
      Re: How to write wide char string literals? Christian Gollwitzer <auriocus@gmx.de> - 2021-07-01 14:01 +0200
        Re: How to write wide char string literals? David Brown <david.brown@hesbynett.no> - 2021-07-01 14:57 +0200
    Re: How to write wide char string literals? Manfred <noname@add.invalid> - 2021-07-01 15:44 +0200

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