C++ Logo

SG16

Advanced search

Subject: Re: Is the concept of basic execution character sets useful?
From: Jens Maurer (Jens.Maurer_at_[hidden])
Date: 2021-02-03 11:40:56


On 03/02/2021 00.09, Corentin wrote:
>
> On Tue, Feb 2, 2021 at 11:57 PM Victor Zverovich <victor.zverovich_at_[hidden] <mailto:victor.zverovich_at_[hidden]>> wrote:
>
> > For the core language, I think we should
> > simply replace "execution character set" with "literal encoding" (narrow and wide),
> > because we never actually care about character sets, just about encoding
>
> I would be very much in favor of this change. "Literal encoding" is exactly what this is and "execution character set" is just confusing. I also agree that it shouldn't be tied to locales in any way.
>
>
> I'd love feedback on the draft I posted earlier in this thread which does that, whenever you have time before the next deadline :)
> A slightly more recent draft is here https://isocpp.org/files/papers/D2297R0.pdf <https://isocpp.org/files/papers/D2297R0.pdf>

My paper is doing the same updates:

https://wiki.edg.com/pub/Wg21telecons2021/SG16/charset.html

I'd suggest to use the terms "ordinary literal encoding" (for char) and
"wide literal encoding" (for wchar_t)
so that "literal encoding" remains available to refer to both, or to
the general concept.

The paper has funny italics (only italicize when defining a term, not when just mentioning it).
It seems to lose the definition of "execution (wide) character set".

I thought we had discussed that the standard library has certain
facilities with locale-dependent character set.
I haven't found a mention of "execution character set" in the library
wording, so I'm interested in learning how these locale-dependent
character sets are described / referenced.

Jens

>
>  
>
> - Victor
>
>
> On Mon, Feb 1, 2021 at 1:22 AM Peter Brett via SG16 <sg16_at_[hidden] <mailto:sg16_at_[hidden]>> wrote:
>
> > -----Original Message-----
> > From: SG16 <sg16-bounces_at_[hidden] <mailto:sg16-bounces_at_[hidden]>> On Behalf Of Jens Maurer via SG16
> > Sent: 30 January 2021 19:26
> > To: sg16_at_[hidden] <mailto:sg16_at_[hidden]>; Hubert Tong <hubert.reinterpretcast_at_[hidden] <mailto:hubert.reinterpretcast_at_[hidden]>>
> > Cc: Jens Maurer <Jens.Maurer_at_[hidden] <mailto:Jens.Maurer_at_[hidden]>>; Corentin <corentin.jabot_at_[hidden] <mailto:corentin.jabot_at_[hidden]>>
> > Subject: Re: [SG16] Is the concept of basic execution character sets useful?
> >
> > > Unfortunately, when that's the case (and I agree that's the case more
> > often than we'd like, another good example is shift-jis/win-1251), string
> > literals cannot be interpreted properly by "locale specific" runtime
> > functions.
> > > Such runtime function expects an encoding that is not the same as the
> > string literal, it cannot interpret it correctly, which can lead to
> > mojibake, etc.
> >
> > From a core language perspective, we have a compile-time encoding for
> > literals
> > (i.e. mapping of character sequences inside literals to code unit
> > sequences).
> >
> > The actual execution environment of the program (possibly conveyed via
> > locale)
> > might not be compatible with that.  For the core language, I think we should
> > simply replace "execution character set" with "literal encoding" (narrow and
> > wide),
> > because we never actually care about character sets, just about encoding,
> > i.e. a sequence of code units with which to initialize a string literal
> > object.
> >
> > Maybe locale-dependent library functions just need to get a divorce from
> > that.
>
> Hi all,
>
> I agree with Jens.
>
> Although in principle a C++ interpreter could somehow make literals appear in a locale-specific encoding, all C++ implementations I'm aware of permanently fix the encoding of string literals at compilation time and before any knowledge of the run-time locale is available.
>
> Furthermore, we want C++ compilers processing a particular corpus of source code to produce the same executable no matter whether the compiler is being run in France, Germany, China or the USA.  Locale can -- should -- obviously affect compiler diagnostics, etc., but these are already implementation-defined and have no impact on the *effect* of processing the program.
>
> I think that it is best to keep all knowledge of locale-dependence in the library.  I like the idea of replacing "execution character set" with "literal encoding" everywhere in the core language.
>
> Best regards,
>
>                          Peter
> --
> SG16 mailing list
> SG16_at_[hidden] <mailto:SG16_at_[hidden]>
> https://lists.isocpp.org/mailman/listinfo.cgi/sg16 <https://lists.isocpp.org/mailman/listinfo.cgi/sg16>
>


SG16 list run by sg16-owner@lists.isocpp.org