Re: [PATCH] Add support for TZ names with <> in tzset

[Brian Inglis <Brian.Inglis@SystematicSw.ab.ca>]

On 2020-11-16 08:13, Corinna Vinschen via Newlib wrote:
> Hi Earle,
> 
> On Nov 14 15:03, Earle F. Philhower, III via Newlib wrote:
>> Howdy all,
>>
>> Attached is a patch which extends the tzset() function to support a format
>> for "unnamed" TZ environment timezones which use "<+/-nn>" as the timezone
>> name instead of an alphabetic name.  These are supported in glibc and are
>> present in several major TZ databases that we use on the ESP8266 Arduino
>> core.  For example,
>>
>>> #define TZ_Africa_Casablanca	  "<+01>-1"
>>
>> The existing tzset sscanf format string breaks at the first "+", assuming
>> it's the
>> beginning of the offset.  This patch special-cases names beginning with "<"
>> to
>> circumvent the issue.
>>
>> Signed-off-by: Earle F. Philhower, III   <earlephilhower@yahoo.com>
> 
> Basically this looks ok.  I have two nits, though.
> 
> - Now that the scanning got more complicated than a single sscanf call,
>    this crys out for a helper function doing the actual scanning for
>    both, std and dst strings.  This could be an inline function which is
>    only inlined
>    #if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
> 
> - The strcat call seems a bit heavy.  What about sth like this instead:
> 
>      __tzname_ptr[n - 1] = '>';
>      __tzname_ptr[n] = '\0';

Should consider modifying the PD TZ project tzcode reference src localtime.c 
tzparse()

	https://github.com/eggert/tz/blob/master/localtime.c#L1069

(contributed to the public domain by Guy Harris): handles all the POSIX rules 
string edge cases to Paul Eggert's satisfaction, and gets patched if any 
upstream org (every distro) or vendor (all OSes) reports a problem.

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

This email may be disturbing to some readers as it contains
too much technical detail. Reader discretion is advised.
[Data in binary units and prefixes, physical quantities in SI.]