[Boost-build] Failing dependency_test.py test.

Subject: [Boost-build] Failing dependency_test.py test.
From: Jurko Gospodnetić (jurko.gospodnetic_at_[hidden])
Date: 2012-07-15 18:19:30

   Hi.

> -d+12 is helpful for this kind of thing.
> It sounds like there could be some kind of spurious dependency.

   Yeah, almost lost my eyesight staring at the -d+3 & -d+12 output 
trying to reason out what is going on.

   My current guess is that there is a problem with generators 
generating multiple targets from a single one and how Boost Jam/Build 
deduces those targets should be rebuilt.

   I've attached the simplest possible test I've managed to reproduce 
the problem with. The test passes (most often) if you set the sleep 
delay used in that test to 0. However, the test fails every time if you 
set it to 2 seconds.

   Updating Boost Jam to support more precise timestamps also makes it 
fail every time - even with the sleep delay set to 0.

   If you or someone else could take a look - I'd be grateful... I hope 
to have the time to look into it again tomorrow or a bit later during 
the week...

>>    Btw. I'm still not positive, but I think there might be a potential
>> problem in that dependency_test.py test (and possibly others using the
>> same implementation pattern) that is causing it fail sporadically with
>> the current implementation but is uncovered completely by using a finer
>> timestamp resolution. It creates CPP & H targets from a FOO target in
>> its foo.foo rule instead of the foo.foo action. That causes those
>> targets to be created every time instead of 'only when needed'.
>
> The print module creates proper updating actions.
> It doesn't write the files immediately.

   Thanks for the tip. I did not really look into how it does its magic, 
but I can see it does not take the information about whether it needs to 
actually touch its file based on whether it is older than its source, so 
I'm guessing it does the rebuild every time. I'll look into this more 
when I get the time next.

   Best regards,
     Jurko Gospodnetić