Re: [RFC][PATCH v4 06/11] Provide backward compatibility for strftime family (bug 10871).

[Rafal Luzynski <digitalfreak at lingonborough dot com>]

Hi,

TL;DR: German language is probably not affected by this bug so will
not be affected by the change. You will not see any difference.
If you thought otherwise that's only because of my lack of precision
and I'm sorry for this.

More details below:

7.11.2016 15:13 Florian Weimer <fweimer@redhat.com> wrote:
>
>
> On 11/05/2016 11:53 AM, Rafal Luzynski wrote:
> > 4.11.2016 14:40 Florian Weimer <fweimer@redhat.com> wrote:
> >>
> >>
> >> On 10/28/2016 02:49 AM, Rafal Luzynski wrote:
> >>> As %OB format specifier has been added to strftime/wcsftime
> >>> family of functions backward compatibility implementation must be
> >>> provided for older binaries which assume that %B returns
> >>> a month name in the nominative case.
> >>
> >> I think this is a misuse of symbol versioning. Why would I want to pick
> >> up this change when compiling from source, but not for existing binaries?
> >>
> >> Florian
> >
> > There may be applications which rely on the fact that "%B"
> > returns the month name in a nominative case. An example is cal(1)
> > which has been pointed out in [1]. Their source code should be
> > changed to use "%OB" but it cannot be expected from the existing
> > binaries.
>
> > You could also ask how to provide the backward compatibility
> > for the applications compiled from source.
>
> Yes, that's what I'm concerned about.
>
> > I think it's impossible and it's been kinda agreed in [2].
>
> I think we should strive to provide backwards compatibility for
> applications and not alter the meaning of %B, and rather change %c to
> use %OB (or whatever the source of the month name in genitive ends up to
> be) instead of %B.

I was considering this approach and I've abandoned it because the only
reason why I was considering it was because I had misread the POSIX
proposal. More details:
https://sourceware.org/bugzilla/show_bug.cgi?id=10871#c39

While at this, changing %c and also %x would be required but insufficient
because applications often use their custom formats like day-month
or weekday-day-month which are neither %c nor %x.

> One example where this matters is German.

It's good that you mention a specific language. My knowledge of German
is next to zero but fortunately I have someone to ask for more details.

> If POSIX requires that %B
> returns the genitive case, as has been suggested,

It seems to me that here is the root of misunderstanding and if it's
caused by my lack of precision then I apologize for this. I have
always used the terms "genitive case" and "nominative case" only
as shortcuts because I should actually say "month name in a form
appropriate when formatting a full date including a day number"
and "month name in a form appropriate when formatting a month name
standalone, without a day number". Occasionally I also refer to
this full expression. There are languages which require genitive
when formatting with date and nominative when standalone; there may
be other languages which require another pair of forms (although
I'm not aware of any such language), and there are languages which
require always one form (nominative) although they also have genitive
form which is not applicable here, an example is German probably.

CLDR refers to "stand-alone" and "format", it seemed to ambiguous to me.
More info:
http://cldr.unicode.org/translation/date-time#TOC-Stand-Alone-vs.-Format-Styles

Now when I look at http://austingroupbugs.net/view.php?id=258
I can see they made the same error: they emphasize genitive and
nominative case while they should emphasize "with a day number"
and "no day number" and put "genitive" and "nominative" in
parentheses only as possible examples of how some languages
implement this feature.

> then all applications
> which currently use %B are broken

Are they broken already? When you type this command:

$ date +"%d %B %Y"

is it broken in German locale? In Polish it's broken, so is in
Czech, Russian, also in Finnish, Greek, and more. If it's also broken
in German then you'll be happy to see the change. If it's not broken
then you don't need any change.

> because I have yet to see a
> mechanically generated German date string which actually needs the
> genitive case. In current usage, they only occur in phrases such “on
> the last Sunday of November”.

Note that a genitive form will be used only if it is provided in
locale data. So if German language has a genitive form but does not
require (or even prohibits) using it when formatting a full date then
all you have to do is not to provide any changes to the locale, just
leave it as is. My patch provides a way to provide two different
forms for month names but this second form is optional. There will
be no change visible if there are no changes in the locale data.
That's the reason why I have also provided sample locale data for
some languages; these changes are not intended to be committed
(although may be committed if translators apparently find them
correct).

In your example, a phrase “on the last Sunday of November” looks
like an attempt to employ strftime() to generate natural language
sentences rather than to format a date. It's been discussed in
bugzilla and stated that strftime() will never be suitable for this.

> Does this clarify my position?
>
> Thanks,
> Florian

I think so and also now I'd like to ask: does this answers your
questions?

Thank you for your participation and support, I'll appreciate
more feedback from you and from other people.

Regards,

Rafal