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Re: C23: asctime is obsolescent

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Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>
>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>
>>> Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>>>
>>>> Richard Damon <Richard@Damon-Family.org> writes:
>>>>
>>>>> On 1/2/23 11:11 AM, Tim Rentsch wrote:
>>>>>
>>>>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>>>>>>
>>>>>>> In the latest C23 draft:
>>>>>>> https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3047.pdf the
>>>>>>> descriptions of the __DATE__ and __TIME__ macros refer to the
>>>>>>> asctime() function.
>>>>>>>
>>>>>>> That's not new.  What's new is that asctime() is deprecated.
>>>>>>>
>>>>>>> Referring to a deprecated function isn't really a problem, but
>>>>>>> if asctime() is actually removed in a future standard the
>>>>>>> descriptions of __DATE__ and __TIME__ will need to be updated.
>>>>>>>
>>>>>>> It would also be nice to have a new macro that expands to the
>>>>>>> current date in the form "YYYY-MM-DD".  I do not suggest
>>>>>>> changing the behavior of __DATE__, but perhaps something like
>>>>>>> __ISODATE__ could be added.  Question:  If this is done,
>>>>>>> should __DATE__ be deprecated?
>>>>>>
>>>>>> It seems pointless to add __ISODATE__ if __DATE__ is retained,
>>>>>> and worse than pointless to add __ISODATE__ and then remove
>>>>>> __DATE__.
>>>>>
>>>>> Why?  What is wrong with having macros to get a value in
>>>>> different formats.  Different applications may well want either
>>>>> one.
>>>>
>>>> To my way of thinking, the symbol __DATE__ is defined in an ISO
>>>> document, so it already qualifies as an ISO date.  To have
>>>> another symbol named __ISODATE__ is redundant if it means the
>>>> same thing as __DATE__, or confusing if it means something
>>>> different.  If it's important to have a symbol for a different
>>>> format defined in some other ISO standard, the symbol name should
>>>> include some indication of where the format comes from, in a
>>>> similar manner to __STDC_IEC_559__, for example.
>>>>
>>>>> Almost all my programs currently use __DATE__ (and __TIME__) to
>>>>> embed build information into the program.  I could see
>>>>> applications where having the ISO formatted date would be
>>>>> useful, as it has some very useful properties (like sortability)
>>>>
>>>> I'm okay with having another date format.  I just don't think the
>>>> symbol that gives it should be named __ISODATE__, because that's
>>>> confusing.
>>>
>>> The format is from ISO 8601, but I would oppose calling the new
>>> macro __ISO_8601_DATE__, because longer and more difficult to
>>> remember.  My intent is to provide an *easy* way to embed the
>>> compilation date as a string in an executable in a reasonable
>>> format.  Inserting "_8601_" into the name doesn't add sufficient
>>> value, and __ISODATE__ is sufficiently clear.  And it's perfectly
>>> possible for the C standard to refer to a YYYY-MM-DD format
>>> without mentioning the ISO 8601 standard.
>>>
>>> The only reason to keep the current __DATE__ in the standard is
>>> backward compatibility (and yes, that's an *extremely* compelling
>>> reason).  If I were adding this to a new language, there would
>>> just be a __DATE__ macro that expands to "YYYY-MM-DD";  it would
>>> never occur to me to build something into the language that
>>> expands to "Mmm DD YYYY".  Adding "ISO" to the new name is a
>>> concession to backward compatibility.
>>>
>>> Not every name has to describe its origin, and nobody seeing the
>>> name __ISODATE__ is going to think that the ISO standard it refers
>>> to is the ISO C standard.  I disagree with your assertion that it
>>> would be confusing.
>>>
>>> And if your problem with the name __ISODATE__ is the "ISO" is
>>> confusing, you could have said that in the first place.
>>
>> To do that I would have had to have known that I was confused,
>> which I didn't.
>
> Are you saying that you weren't confused, or that you were confused
> and didn't know it?

I wasn't confused.  I was wrong, but I wasn't confused.

>>> Do you have a suggestion for a better name?
>>
>> Yes, a more explicit one, including a numeric indicator of
>> which ISO standard it's from (and it's likely there is more
>> than one possibility).
>
> You're replying to something I wrote about six months ago.

Yes, I'm sorry it took so long.  It's been a hard year.

> When I asked whether you have a suggestion, I was also
> implicitly asking what your suggestion is.  Perhaps you'll let
> us know before the end of the year.

I already gave a suggestion.  I don't at this moment have enough
information to make that suggestion more specific.

>> I consulted with someone whose job it is to ensure ISO
>> compliance in an industry that takes ISO compliance
>> seriously, and she absolutely agreed with this reaction.
>> These markers should ALWAYS be explicit.  Ambiguity is
>> the enemy.  I would think that you of all people would
>> agree with this position.
>
> Names don't have to be fully descriptive.  "size_t" doesn't say
> that the size is measured in bytes, or that the "t" stands for
> "type".  It doesn't have to.  The meaning is specified in the
> standard.

This case is one where I believe it would be prudent for the
particular ISO reference to be explicit in the name, and not just
given indirectly in text in the C standard.

> I already gave my reasons for not wanting the proposed new name
> to be "__ISO_8601_DATE__".  All I'm looking for is something
> that's reasonably clear and distinct from "__DATE__".

Yes, I think I understand your reasoning.  I don't share your
conclusions, as I have tried to explain.

> If such a symbol were added, the standard would have to
> describe its semantics precisely, with or without referring to
> the ISO 8601 standard.

If the generated date string is meant to conform to a particular
format defined in an ISO standard, then it seems like good
practice would dictate that a reference to the specific ISO
standard document should be given in the C standard, and also
listed as a normative reference.

> I'd also be happy with a name like "__YYYYMMDD__" or "__YMD__".

If the point, or at least part of the point, is to present a date
in a format that conforms to one given in an ISO standard, then
it seems a good idea to make that apparent in the name.  In this
very particular case, more explicit is better.

And there is nothing stopping someone from using a #define'd
symbol

    #define DATE_YYYYMMDD __ISO_8601_DATE__

if they want to use a name that is more directly descriptive and
perhaps easier to remember.

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C23: asctime is obsolescent Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-11-23 18:12 -0800
  Re: C23: asctime is obsolescent Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-02 08:11 -0800
    Re: C23: asctime is obsolescent Richard Damon <Richard@Damon-Family.org> - 2023-01-02 12:11 -0500
      Re: C23: asctime is obsolescent Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-29 10:33 -0800
        Re: C23: asctime is obsolescent Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-29 16:49 -0800
          Re: C23: asctime is obsolescent Pete Forman <petef4+usenet@gmail.com> - 2023-01-30 23:23 +0000
          Re: C23: asctime is obsolescent Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-07-20 10:11 -0700
            Re: C23: asctime is obsolescent Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-07-20 15:04 -0700
              Re: C23: asctime is obsolescent Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-08-13 15:26 -0700
                Re: C23: asctime is obsolescent Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-08-13 16:47 -0700
                Re: C23: asctime is obsolescent Jakob Bohm <jb-usenet@wisemo.com.invalid> - 2023-08-17 21:18 +0200
                Re: C23: asctime is obsolescent Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-08-17 13:14 -0700
                Re: C23: asctime is obsolescent Jakob Bohm <jb-usenet@wisemo.com.invalid> - 2023-08-18 01:26 +0200
                Re: C23: asctime is obsolescent Pete Forman <petef4+usenet@gmail.com> - 2023-08-21 17:42 +0100
                Re: C23: asctime is obsolescent Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-08-29 02:37 -0700
    Re: C23: asctime is obsolescent Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-02 16:47 -0800
      Re: C23: asctime is obsolescent David Brown <david.brown@hesbynett.no> - 2023-01-03 09:40 +0100
      Re: C23: asctime is obsolescent Pete Forman <petef4+usenet@gmail.com> - 2023-01-03 15:15 +0000
        Re: C23: asctime is obsolescent Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-03 10:35 -0800
        Re: C23: asctime is obsolescent Phil Carmody <pc+usenet@asdf.org> - 2023-01-04 18:22 +0200
          Re: C23: asctime is obsolescent James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-04 15:04 -0500
      Re: C23: asctime is obsolescent Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-29 10:43 -0800
  Re: C23: asctime is obsolescent Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-02 08:20 -0800
  Re: C23: asctime is obsolescent Kaz Kylheku <864-117-4973@kylheku.com> - 2023-07-20 17:29 +0000
    Re: C23: asctime is obsolescent Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-07-20 15:20 -0700

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