Support non-POSIX TZ strings

[Brian Inglis]

On 2022-02-14 14:33, Jeff Johnston wrote:
> On Mon, Feb 14, 2022 at 3:46 PM Brian Inglis <
> Brian.Inglis@systematicsw.ab.ca> wrote:
> 
>> On 2022-02-14 12:58, jdoubleu wrote:
>>> On 22-02-14 10:10-0700, Brian Inglis wrote:
>>
>>>> [..] but we should start with the actual POSIX spec under TZ
>>
>>> Yes, that is exactly what I meant: Newlib supporting the <> (angle
>>> brackets) syntax.
>>> I didn't know that it was actually part of POSIX spec, since so many
>>> libs actually don't implement it.
>>
>> Most should have by now if maintained: we should be a laggard! ;^>
>>
>>>> The BSD or TZcode implementations could probably be adapted [..]
>>
>>> It looks like the TZcode implementation by Paul Eggert uses a different
>>> approach to parsing the strings, than the current implementation in
>>> newlib
>>> (
>> https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=newlib/libc/time/tzset_r.c).
>>
>>> I'm not sure, if you want to copy the code over or use changes by e.g.
>>> Earle F. Philhower from
>>> https://github.com/earlephilhower/newlib-xtensa/pull/14.
>>> Because of the above question, I'm not sure how to continue on this. I
>>> would like to contribute myself and submit an implementation, but I'll
>>> wait for feedback by other maintainers, first.
>>
>> Upstream sources like BSDs or TZcode official reference implementations
>> are normally preferred because they are feature complete, regularly
>> maintained, feature test and standards compliant, vulnerabilities
>> checked, issues reported, and promptly fixed.
>>
>> I checked the BSDs and they seem to have adopted or adapted the TZcode
>> official reference implementation, so I am not sure from where it may
>> have been adopted, or whether it is original: the maintainer Jeff
>> Johnson may remember.

> Unfortunately, I do not remember the exact details from back then.  With no
> license header, it means it was written by Cygnus/Red Hat.

>> I also wonder if the GMT defaults should be updated to UTC.

Submitted a newlib patch which builds okay, but cannot test, as I don't 
have a newlib platform to run on, and Cygwin uses it's own TZ DB code base.
It should accept up to 10 character abbreviations for STD and DST 
matching POSIX specs including anything within < > quoted content.
If someone needing this could build, test, and send feedback, I'd 
appreciate it.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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