[systemd-devel] How to set time from Perl

[Daniel P. Berrange]

On Mon, Sep 07, 2015 at 04:23:42PM +0200, Manuel Reimer wrote:
> Hello,
> 
> if I run the following code on an intel based platform, then I don't have
> any problems:
> 
>   use Net::DBus;
>   my $bus = Net::DBus->system();
>   my $logind = $bus->get_service('org.freedesktop.timedate1');
>   my $manager = $logind->get_object('/org/freedesktop/timedate1',
>                                     'org.freedesktop.timedate1');
>   $manager->SetTime($time * 1000000, 0, 0);
> 
> The variable "$time" is in seconds.
> 
> If I run this to an ARM based system, then I get the folowing time:
> 
>   # date
>   Thu Jan  1 01:00:02 CET 1970
> 
> Does someone have an idea why this doesn't work?

By "ARM system" do you mean 32-bit ArmV7, or 64-bit AArch64 ?

Based on the behaviour you describe, I'm thinking you are most
likely on 32-bit ArmV7.  Perl integers on 32-bit are only 32-bit
in length, and the SetTime() method needs a 64-bit integer,
since it is representing the time in microseconds. So when you
do $time * 1000000 you are probably getting integer truncation.

Net::DBus can deal with 64-bit integers, but you need to provide
them as the Perl string type, not integer type, so Net::DBus XS
module can do a safe conversion to 64-bit without truncation.

So instead of doing

  $manager->SetTime($time * 1000000, 0, 0);

try doing

  $manager->SetTime($time . "000000", 0, 0);

which will conmvert $time to string type, and then append 6
zeros.

Regards,
Daniel
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