[RTEMS Project] #2697: Function for getting a time_t from a struct tm in UTC (like timegm on Linux and BSD)

[RTEMS trac]

#2697: Function for getting a time_t from a struct tm in UTC (like timegm on Linux
and BSD)
--------------------------------+-------------------
 Reporter:  Christian Mauderer  |       Owner:
     Type:  enhancement         |      Status:  new
 Priority:  normal              |   Milestone:
Component:  Newlib              |     Version:  4.12
 Severity:  normal              |  Resolution:
 Keywords:                      |
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Comment (by Christian Mauderer):

 It seems that the solution in the crypto library is a simplified one that
 does not care for leap seconds or similar. To be honest, I had not found
 this one. But I found three others in freebsd:

 * A comprehensive implementation can be found in the tzcode area:
 https://github.com/freebsd/freebsd/blob/master/contrib/tzcode/stdtime/localtime.c
   This implementation uses the same functions for mktime and timegm.

 * Another implementation in ldns uses the solution from the man page. But
 that is not thread save:
 https://github.com/freebsd/freebsd/blob/master/contrib/ldns/compat/timegm.c

 * A third implementation is in the ntp area:
 https://github.com/freebsd/freebsd/blob/master/contrib/ntp/libntp/mktime.c

 As far as I can see, the one from tzcode is the one that handles the most
 details. It might would make sense to use this implementation for mktime
 as well as timegm

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Ticket URL: <http://devel.rtems.org/ticket/2697#comment:4>
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