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Date:	Sat, 30 Oct 2010 13:53:11 -0400
From:	Ken Brown <kbrown AT cornell DOT edu>
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To:	cygwin AT cygwin DOT com
Subject:	Re: localtime and TZ
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On 10/30/2010 8:58 AM, Ken Brown wrote:
>> I've looked at Cygwin's localtime.cc, and the behavior I'm complaining
>> about is caused by the following code at the beginning of tzset:
>>
>> 	const char *	name = getenv("TZ");
>>
>> 	if (name == NULL) {
>> 		if (!lcl_is_set)
>> 			tzsetwall();
>> 		goto out;
>> 	}
>>
>> So getting rid of 'if (!lcl_is_set)' would solve the problem.  But this
>> would be inefficient, because it would mean that tzsetwall gets called
>> every time tzset is called if TZ is never set.  To get around that, one
>> could have tzsetwall set TZ.
>>
>> It seems that tzset and tzsetwall used to behave the way I'm proposing
>> before the following two changes were made:
>>
>> 2007-12-11  Corinna Vinschen<corinna AT vinschen DOT de>
>>
>> 	* localtime.cc (tzset): Call tzsetwall only if it hasn't been
>> 	called before.
>>
>> 2007-08-01  Corinna Vinschen<corinna AT vinschen DOT de>
>>
>> 	* localtime.cc (tzsetwall): Don't set TZ.
>
> I've just found the reason for the 2007-08-01 change:
>
>     http://www.cygwin.com/ml/cygwin/2007-08/msg00041.html
>
> So I don't know what should be done.

How's the attached patch?  I'm not set up to build cygwin1.dll, so I 
can't test it right now.  I hope the intent is clear in case I got 
something wrong.

Ken

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--- localtime.cc.orig	2009-06-14 05:35:35.000000000 -0400
+++ localtime.cc	2010-10-30 13:28:36.421875000 -0400
@@ -597,6 +597,7 @@
 static char		lcl_TZname[TZ_STRLEN_MAX + 1];
 static int		lcl_is_set;
 static int		gmt_is_set;
+static int		TZ_is_set;
 
 #define tzname _tzname
 #undef _tzname
@@ -1479,11 +1480,14 @@
 	const char *	name = getenv("TZ");
 
 	if (name == NULL) {
-		if (!lcl_is_set)
+		if (!lcl_is_set || TZ_is_set) {
+			TZ_is_set = 0;
 			tzsetwall();
+		}
 		goto out;
 	}
 
+	TZ_is_set = 1;
 	if (lcl_is_set > 0  &&  strcmp(lcl_TZname, name) == 0)
 		goto out;
 	lcl_is_set = (strlen(name) < sizeof (lcl_TZname));


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