Subject: Re: [SG16-Unicode] P1208R3 / source_location
From: Corentin (corentin.jabot_at_[hidden])
Date: 2019-02-18 11:20:32
Quick reply : display only, no expectation the file can be open, or exists,
or is a file. It's purely informative. But expectation it can be displayed,
the main use cases being logging. Otherwise I agree with you.
On Mon, Feb 18, 2019, 7:16 AM Tom Honermann <tom_at_[hidden]> wrote:
> On Feb 18, 2019, at 10:04 AM, Corentin <corentin.jabot_at_[hidden]> wrote:
> Very good points.
> Wouldn't it be sufficient to specify that the strings are NTMBS encoded
> using the execution character set?
> source_location currently avoids making any assumption about how these
> strings are formed, including that they are derived from a source file.
> So since the value is implementation-defined, so should be the way it's
> However, it is reasonable to assume that these things are valid text and
> therefore have a known encoding.
> Adding Tom, because this is borderline SG16 territory.
> This isnât borderline as we have (recently) requested review of anything
> involving file names.
> @Tom: Do you want to see source_location this week knowing that I'd hope
> it would get through LWG before the end of the week?
> Or do you think having function_name / filename as multi-bytes strings
> encoded using the execution character set is reasonable?
> The alternative I see are
> - Leave it unspecified
> - Force a specific character set... which the world is not ready for
> I think there is a higher level question to answer. Are the provided file
> names display only, or should one expect to be able to open the file using
> the provided name?
> If they are display only, then we can specify an encoding for them
> similarly to what is done for member functions of std::filesystem::path. In
> this case, we must explicitly acknowledge that the names do not roundtrip
> through the filesystem (though typically will in practice). Note that, on Windows,
> file names cannot be represented accurately using char based strings, so
> unless we want to add wchar_t support, these names will be technically
> display only.
> If they are potentially not display only, then we canât associate an
> encoding and the names are bags-of-bytes. This is a limitation of POSIX.
> But then we need wchar_t support for Windows.
> In San Diego, the guidance we gave for the stacktrace proposal is that
> file names are implementation defined bags-of-bytes. If we advised
> otherwise for source location, we would be giving inconsistent guidance.
> I think we should discuss this in SG16 this week. Not necessarily to
> propose changes for the proposal, but to solidify our collective thinking
> around file names.
> On Mon, 18 Feb 2019 at 03:56 Axel Naumann <Axel.Naumann_at_[hidden]> wrote:
>> Hi Robert,
>> Regarding your P1208R3:
>> Nit: it's titled "D1208R3", it doesn't mention email addresses.
>> Not-so-nit: a NB comment on the reflection TS asks to not use NTBS but
>> NTMBS and "Where NTBS is mentioned in the document under ballot, the
>> encoding used for the stringâs value is unspecified." Jens agrees that
>> the proposed solution should be applied: "Specify that the strings are
>> first formed using the basic source character set (with
>> universal-character-names as necessary) then mapped in the manner
>> applied to string literals with no encoding prefix in phases 5 and 6 of
>> I would very much hope that both changes are also applied to P1208R3. I
>> call this out explicitly in our recommended NB comment response paper.
>> Cheers, Axel.
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