%ENV{TZ} does not always affect CORE::localtime() under multi-threaded perl

[dda]

Hi Monks!

Consider the following code:

$ENV{TZ} = "DST";   # something different than current TZ
print localtime();

The code does not work properly at each invocation. Looks like $ENV{TZ} is cached somewhere. If I add some debug messages, like 'warn "$ENV{TZ}"', before calling localtime(), it works always.

The problem exists only at one of our linux boxes, with perl, v5.8.0 built for i386-linux-thread-multi. Another machines with perl 5.6.1, single-treaded, are not affected.

Probably it is a known issue?

--dda

[Chmrr]

This is a problem on the C level, I believe. The localtime(3) call does not always check the current value of the TZ environment variable. To force it to do so, POSIX-compliant systems should use the tzset(3) call.

You can imitate this in perl via:

use POSIX; $\ = "\n";
$ENV{TZ} = "EST";
POSIX::tzset();
print scalar localtime();
$ENV{TZ} = "DST";
POSIX::tzset();
print scalar localtime();

perl -pe '"I lo*`+$^X$\"$]!$/"=~m%(.*)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'

[dtr]

This works fine from a script, but does not work under mod_perl_2! Do you have any suggestions as to how I might go about getting this working under mod_perl_2?????

[The Mad Hatter]

I have perl v5.8.0 built for i686-linux-thread-multi-ld and doing

perl -e '$ENV{TZ} = "DST";print scalar localtime(), "\n";'

works fine for me.

[dda]

Could you please try this:

perl -e '$ENV{TZ} = "EST";print scalar localtime(), "\n";$ENV{TZ} 
= "DST";print scalar localtime(), "\n";'

It works correctly at 5.6.1 and misbehaves at 5.8.0

--dda

[Anonymous Monk]

What dda means to say is:

here is the output on a redhat 8, perl 5.8.0 (multithreaded) box (actually we have tried 3 redhat 8 boxes):

perl -e '$ENV{TZ} = "EST";print scalar localtime(), "\n";$ENV{TZ} = "DST";print scalar localtime(), "\n";'
Wed Apr 16 15:47:41 2003
Wed Apr 16 15:47:41 2003


whereas on a redhat 7.2, perl 5.6.1 box, the output is
Wed Apr 16 15:42:25 2003
Wed Apr 16 20:42:25 2003


and on a freebsd box, perl 5.8.0, the output is also correct, i.e.
Wed Apr 16 15:42:25 2003
Wed Apr 16 20:42:25 2003

perl 5.6.1 under cygwin seems to manifest the problem also.

[The Mad Hatter]

Hmmmm, I see what you mean. Seems like a bug (like you said).

Just to let every know, output is:

Wed Apr 16 15:56:22 2003
Wed Apr 16 15:56:22 2003