Subject: Re: broken djgpp 1.12 timezone functions
To: roe2 AT midway DOT uchicago DOT edu (Cave Newt)
Date: Tue, 23 Aug 1994 09:55:35 +0200 (MET DST)
From: Henrik Storner <storner AT olicom DOT dk>
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu

I haven't seen any response to this on the list, so I thought I'd share
my experiences with you all:

roe2 AT midway DOT uchicago DOT edu writes, in a message from Aug. 15th:

> I've just been investigating djgpp's handling of timezone information,
> and basically (forgive my bluntness) it's just plain wrong.

[...]

> stat() simply assumes everybody lies four hours west of GMT.  The use 
> of the TZ variable and the tzset() (initialization) function had 
> absolutely no effect on the time returned by stat().  Bug #1.

Confirmed. stat() is definitely broken here.


> The second path, and the one chosen by whoever did the djgpp port of
> UnZip, is to use the Berkeley ftime() function.  This, at least, is
> vaguely in the ballpark

I have found that time(), ftime(), localtime() and gmtime() behave correct-
ly ONLY if you set up TZ as per Posix standard. For my timezone, that would
mean:

    TZ=MET-1METDST-2,M3.5.0/02:00,M9.5.0/02:00

which is not quite intuitive. ftime() does not return the correct information
about timezone offsets/daylight savings time usage, though.

> djgpp 1.12 using ftime():
>   with no TZ variable:  timezone adds 5 hours; DST adds zero      ok...
>   with TZ=PST8:         timezone adds 8 hours; DST adds zero      good
>   with TZ=PST8PDT:      timezone adds zero; DST adds zero         WRONG

I traced through the tzset() function in the library sources. Pretty com-
plicated stuff. It seems that just specifying the ...PDT part without
giving the specific times that DST takes effect is not handled correctly;
tzload() - an internal function in the ctime.c library module - bails
out and acts as if NO TZ setting is in effect.
-- 
Henrik Storner        | "Man is the best computer we can put aboard a space-
(storner AT olicom DOT dk)   |  craft ... and the only one that can be mass produced 
System Engineering    |  with unskilled labor."
Olicom Denmark        |                                   Wernher von Braun