> I'm concerned that deployment experience might be limited to specific
environments.

The great thing about the current implementation (and proposal) is that it
is consistent with printf's behavior on common C standard library
implementations on non-Windows platforms, so we have all the deployment
experience in the world. This is also why I am reluctant to innovate in
this area. There has been a lot of usage experience on Windows as well and
there is much less variation there.

> I think the non-Unicode function is awkwardly named.

Naming suggestions are welcome!

Cheers,
Victor

On Wed, May 12, 2021 at 12:51 PM Hubert Tong <
hubert.reinterpretcast_at_[hidden]> wrote:

> On Wed, May 12, 2021 at 3:14 PM Victor Zverovich <
> victor.zverovich_at_[hidden]> wrote:
>
>> Hi Hubert,
>>
>> Thanks for the suggestions, I'll try incorporating them in the next
>> iteration of the paper.
>>
>> > I think it would help if the point was stated more explicitly ...
>>
>> Good idea, will clarify this.
>>
>> > The paper can at least acknowledge that "polyglot" string literals
>> exist ...
>>
>> Sure.
>>
>> > we'll end up with cases where the literal encoding is UTF-8 but the
>> user won't want the UTF-8 std::print behaviour to potentially kick in.
>>
>> I am a bit skeptical because I haven't seen any reports about cases like
>> this from the extensive usage experience of this feature. We can't fix
>> clearly broken things and be bug-to-bug compatible with legacy APIs at the
>> same time.
>>
>> > At least two cases come to mind.
>>
>> I don't think we can do much if users decide to lie about the encoding.
>> We should make the common case work rather than try making everyone happy
>> and support theoretical use cases not backed by actual implementation and
>> usage experience.
>>
>
> I'm concerned that deployment experience might be limited to specific
> environments. I expect the conditions for the second scenario are met very
> easily on *nix and also very difficult to test for (requires some sort of
> special test environment/harness).
>
>
>> That said they can always use nonunicode function or continue using their
>> legacy APIs in those cases.
>>
>
> I think the non-Unicode function is awkwardly named.
>
>
>>
>> Cheers,
>> Victor
>>
>>
>>
>>
>> On Tue, May 11, 2021 at 8:23 PM Hubert Tong <
>> hubert.reinterpretcast_at_[hidden]> wrote:
>>
>>> On Tue, May 11, 2021 at 8:41 PM Victor Zverovich via SG16 <
>>> sg16_at_[hidden]> wrote:
>>>
>>>> Dear Unicoders,
>>>>
>>>> Here is a link to a new revision of P2093:
>>>> https://isocpp.org/files/papers/D2093R6.html. It's essentially the
>>>> same as R5 but addresses the latest LEWG feedback and adds a few
>>>> clarifications. The only change to the wording is replacing <io> with
>>>> <print>.
>>>>
>>>
>>> Thanks Victor.
>>>
>>> With respect to the choice to transcoding, it took me a while to catch
>>> on to the statement being made. I think it would help if the point was
>>> stated more explicitly that the choice to perform replacement during
>>> transcoding is because that is consistent with the treatment of malformed
>>> UTF-8 for UTF-8-native terminals and the choice not to transcode in the
>>> case where the terminal is UTF-8 native is because we expect the terminal
>>> to behave predictably as-is we did do the "transcoding".
>>>
>>> I'm still not entirely convinced about the argument surrounding the
>>> choice of using the literal encoding though. The paper can at least
>>> acknowledge that "polyglot" string literals exist and partially obviates
>>> the insistence that the literal encoding being UTF-8 according to the build
>>> system/build mode means that the involvement of non-UTF-8 strings in the
>>> vicinity of std::print constitutes "mixing encodings".
>>>
>>> I really think that, just for predictability surrounding the display of
>>> substitution text, we'll end up with cases where the literal encoding is
>>> UTF-8 but the user won't want the UTF-8 std::print behaviour to potentially
>>> kick in.
>>>
>>> At least two cases come to mind:
>>> (1) Printing using both legacy interfaces and std::print where the
>>> legacy interfaces are not using UTF-8 may appear fine on some terminals but
>>> would result, on redirect, in output with mixed encoding.
>>>
>>> (2) std::print where the literal encoding is UTF-8 but the literals are
>>> all "polyglot" and substitution strings that are not UTF-8 can appear to be
>>> okay when redirecting or printing to non-Unicode terminals; however, once
>>> deployed to a Unicode terminal, replacement characters show up (even if the
>>> output is properly encoded for the underlying C output interface).
>>>
>>>
>>>>
>>>> Cheers,
>>>> Victor
>>>>
>>>> On Tue, May 11, 2021 at 11:02 AM Tom Honermann via SG16 <
>>>> sg16_at_[hidden]> wrote:
>>>>
>>>>> Reminder that this meeting is taking place tomorrow.
>>>>>
>>>>> Per suggestion by Peter, the agenda order is being changed to review
>>>>> the updates in P2295R2 before D2372R1 and P2093R5 in the hopes that we can
>>>>> forward P2295R2 to EWG. We'll try to limit that discussion to 30 minutes.
>>>>> The updated agenda is below. Again, we are unlikely to get to P2348R0 at
>>>>> all.
>>>>>
>>>>> - P2295R2: Support for UTF-8 as a portable source file encoding
>>>>> <https://wg21.link/p2295r3>
>>>>> - Review updates intended to address prior SG16 feedback.
>>>>> - D2372R1: Fixing locale handling in chrono formatters
>>>>> <https://isocpp.org/files/papers/D2372R1.html>
>>>>> - Affirm or rebut LEWGs position.
>>>>> - P2093R5: Formatted output <https://wg21.link/p2093r5>
>>>>> - Discuss locale dependent character encoding concerns.
>>>>> - P2348R0: Whitespaces Wording Revamp
>>>>> <https://wg21.link/p2348r0>
>>>>>
>>>>> Tom.
>>>>>
>>>>> On 5/4/21 12:06 AM, Tom Honermann via SG16 wrote:
>>>>>
>>>>> SG16 will hold a telecon on Wednesday, May 12th at 19:30 UTC (timezone
>>>>> conversion
>>>>> <https://www.timeanddate.com/worldclock/converter.html?iso=20210512T193000&p1=1440&p2=tz_pdt&p3=tz_mdt&p4=tz_cdt&p5=tz_edt&p6=tz_cest>
>>>>> ).
>>>>>
>>>>> The agenda is:
>>>>>
>>>>> - D2372R1: Fixing locale handling in chrono formatters
>>>>> <https://isocpp.org/files/papers/D2372R1.html>
>>>>> - Affirm or rebut LEWGs position.
>>>>> - P2093R5: Formatted output <https://wg21.link/p2093r5>
>>>>> - Discuss locale dependent character encoding concerns.
>>>>> - P2295R2: Support for UTF-8 as a portable source file encoding
>>>>> <https://wg21.link/p2295r3>
>>>>> - Review updates intended to address prior SG16 feedback.
>>>>> - P2348R0: Whitespaces Wording Revamp
>>>>> <https://wg21.link/p2348r0>
>>>>>
>>>>> Our last telecon was consumed by discussion
>>>>> <https://github.com/sg16-unicode/sg16-meetings/blob/master/README.md#april-28th-2021>
>>>>> of LWG3547 <https://cplusplus.github.io/LWG/issue3547> and possible
>>>>> remedies. Though we did not reach consensus on a direction forward during
>>>>> that telecon, Victor and Corentin, at the LEWG chair's request, drafted
>>>>> D2372R0, presented it at the LEWG telecon held 2021-05-03
>>>>> <https://wiki.edg.com/bin/view/Wg21telecons2021/P2372#2021-05-03>,
>>>>> and LEWG reached strong consensus for it. The D2372R0 revision will be
>>>>> submitted for the May mailing as P2372R0; and a D2372R1
>>>>> <https://isocpp.org/files/papers/D2372R1.html> revision addressing
>>>>> LEWG feedback will be submitted as P2372R1. Both revisions substantially
>>>>> match the proposed resolution that SG16 discussed. Since SG16 did not
>>>>> reach consensus on that direction, the LEWG chair has asked that we revisit
>>>>> it to either affirm or rebut the LEWG consensus. We will therefore
>>>>> (briefly) discuss and then poll that direction. Note that the poll taken
>>>>> in SG16 differs from the poll taken in LEWG. In SG16, we polled applying
>>>>> the proposed resolution to C++23 while LEWG polled applying the proposed
>>>>> resolution (with amendments to not change behavior for iostream
>>>>> manipulators) to C++23 *and* retroactively to C++20.
>>>>>
>>>>> Once we've dispatched D2372R1, we'll return to the original agenda for
>>>>> our last telecon; discussion of P2093R5 <https://wg21.link/p2093r5>
>>>>> (Formatted output) and P2295R2 <https://wg21.link/p2295r3> (Support
>>>>> for UTF-8 as a portable source file encoding). I've retained P2348R0
>>>>> <https://wg21.link/p2348r0> on the agenda, though I don't expect that
>>>>> we'll get to it.
>>>>>
>>>>> With regard to P2093R5 <https://wg21.link/p2093r5>, the current
>>>>> status is that LEWG has referred the paper back to SG16 for further
>>>>> discussion; please see the LEWG meeting minutes here
>>>>> <https://wiki.edg.com/bin/view/Wg21telecons2021/P2093#Library-Evolution-2021-04-06>.
>>>>> Specifically, LEWG would benefit from additional analysis of previously
>>>>> deferred questions <http://lists.isocpp.org/lib-ext/2021/03/18189.php>
>>>>> regarding character encoding concerns, transcoding requirements (or the
>>>>> lack there of) and the ensuing consequences (or lack there of).
>>>>>
>>>>> 1. How errors in transcoding should be handled. E.g., when
>>>>> transcoding from UTF-8 to a UTF-16 based console interface and the UTF-8
>>>>> input is not well-formed.
>>>>> 2. The choice to base behavior on the compile-time choice of
>>>>> literal encoding. An implication of the current proposal is that a program
>>>>> that contains only ASCII characters in string literals will change behavior
>>>>> depending on whether the literal encoding is UTF-8 vs ASCII (or some other
>>>>> ASCII derived encoding).
>>>>> 3. Whether transcoding to the console interface encoding should be
>>>>> performed when the literal encoding is not UTF-8.
>>>>> 4. What the implications are for future support of std::print("{}
>>>>> {} {} {}", L"Wide text", u8"UTF-8 text", u"UTF-16 text", U"UTF-32
>>>>> text").
>>>>>
>>>>> I think these concerns will be easier to resolve if we first reach
>>>>> consensus regarding scenarios in which localized text may be provided in an
>>>>> unexpected encoding. The following is a slightly modified example of code
>>>>> Hubert previously provided. The example has been modified to explicitly
>>>>> opt into localized chrono formatting.
>>>>>
>>>>> std::print("{:L%p}\n",
>>>>> std::chrono::system_clock::now().time_since_epoch());
>>>>>
>>>>> At issue is the encoding used by locale sensitive chrono formatters.
>>>>> The example above contains the %p specifier and is locale sensitive
>>>>> because AM/PM designations may be localized. In a Chinese locale the
>>>>> desired translation of "PM" is "下午", but the locale will provide the
>>>>> translation in the locale encoding. As specified in P2093R5, if the
>>>>> literal encoding is UTF-8, than std::print() will expect the
>>>>> translation to be provided in UTF-8, but if the locale is not UTF-8-based
>>>>> (e.g., Big5; perhaps Shift-JIS for the Japanese 午後 translation), then the
>>>>> result is mojibake.
>>>>>
>>>>> I had previously suggested the following possible directions we can
>>>>> investigate to resolve the encoding concerns.
>>>>>
>>>>> - Specialize std::locale facets
>>>>> <https://en.cppreference.com/w/cpp/locale/locale> and related I/O
>>>>> manipulators like std::put_time()
>>>>> <https://en.cppreference.com/w/cpp/io/manip/put_time> for char8_t.
>>>>> This would allow std::print() to, when the literal encoding is
>>>>> UTF-8, opt-in to use of the UTF-8/char8_t facets and I/O
>>>>> manipulators.
>>>>> - When the literal encoding is UTF-8, stipulate that running the
>>>>> program in a non-UTF-8 based locale is non-conforming. This would
>>>>> effectively require MSVC programmers to, when building code with the
>>>>> /utf-8 option, to also force selection of a UTF-8 code page via a
>>>>> manifest
>>>>> <https://docs.microsoft.com/en-us/windows/uwp/design/globalizing/use-utf8-code-page>
>>>>> and require use of Windows 10 build 1903 or later.
>>>>> - When the literal encoding is UTF-8, specify that non-UTF-8 based
>>>>> locale dependent translations be implicitly transcoded (such transcoding
>>>>> should never result in errors except perhaps for memory allocation
>>>>> failures).
>>>>> - Drop the special case handling for the literal encoding being
>>>>> UTF-8 and specify that, when bypassing a stream to write directly to the
>>>>> console, that the output be implicitly transcoded from the current locale
>>>>> dependent encoding (whatever it is) to the console encoding (UTF-8).
>>>>>
>>>>> If we get through all of that, we'll review Corentin's updates in
>>>>> P2295R2 <https://wg21.link/p2295r3> to address prior SG16 feedback.
>>>>> Thank you to everyone that already provided additional feedback on the
>>>>> mailing list!
>>>>>
>>>>> Tom.
>>>>>
>>>>>
>>>>> --
>>>>> SG16 mailing list
>>>>> SG16_at_[hidden]
>>>>> https://lists.isocpp.org/mailman/listinfo.cgi/sg16
>>>>>
>>>> --
>>>> SG16 mailing list
>>>> SG16_at_[hidden]
>>>> https://lists.isocpp.org/mailman/listinfo.cgi/sg16
>>>>
>>>