[MonoTouch] Did Threading change a lot in 5.2.latest?

[Nic Wise]

... and after some debugging...with a drumroll but NO surprise, it
looks like the problem is.... ME.

NullReferenceException in the ContinueWith section. Causes a segfault.
Basically:

foo.Property = value;

foo is null (it's a derivative from MT.D's Element). bang. (Property
does nothing except assignment)

try/catch doesn't catch it tho. Which is ODD.



On Thu, Mar 15, 2012 at 10:53, Nic Wise <nicw at fastchicken.co.nz> wrote:
> It's not (I think!) that TF is catching the error - its that the app
> crashes if I use TFLog (which is async under the hood)
>
> But it could be the ContinueWith thats throwing an exception, which is
> tearing down the initially created thread, and possibly the
> (TFLog-create) child thread, too....
>
> I'll post the TF-generated crash report once TF is back up....
>
>
>
> On Thu, Mar 15, 2012 at 10:49, Rolf Bjarne Kvinge <rolf at xamarin.com> wrote:
>> Hi,
>>
>> These issues might be related. Have in mind that TestFlight will handle
>> NullReferenceExceptions as crashes (and won't let you catch them).
>>
>> Rolf
>>
>> On Thu, Mar 15, 2012 at 11:39 AM, Nic Wise <nicw at fastchicken.co.nz> wrote:
>>>
>>> Hi there
>>>
>>> I'm having a few issues in the newest versions of MT, mostly around
>>> Threading (ok, ALL around threading).
>>>
>>> this one is a fairly major, but easy to work around, one for me:
>>>
>>> https://bugzilla.xamarin.com/show_bug.cgi?id=3676
>>>
>>> I'm getting it when I use NewtonSoft Json.net from a thread. I worked
>>> around it by using it from the UI thread, and caching the resulting
>>> object (not a big deal at all in this case). The DLL I'm using hasn't
>>> changed for a long time.....
>>>
>>>
>>>
>>> However, I'm also having an issue with TestFlight's logging. If I log
>>> in a thread, sometimes, I get a segfault. Not every time, but always
>>> in the same place, and ALWAYS in a thread. The thread code is like
>>> this:
>>>
>>> Task.Factory.StartNew(() => {
>>>                                CalculateSummary ();
>>>                        }).ContinueWith(t => {
>>>                                if (oncomplete != null) oncomplete();
>>>                        }, new UIKitScheduler());
>>>
>>> (UIKitScheduler is this: https://gist.github.com/1431457 )
>>> CalculateSummary loads a bunch of stuff from SQLite, then the last line
>>> is:
>>>
>>> Util.Log ("recalculating took {0}ms".Fmt (sw.ElapsedMilliseconds));
>>>
>>> It is possible that the oncomplete is throwing an error, which I need
>>> to check out - I've had issues with threading disappearing if the
>>> continue throws an uncaught exception.
>>>
>>> Anywho, Util.Log does a Debug.WriteLine (or Console.WriteLine, same
>>> result), and a TestFlight.Log. The first works always. The latter
>>> crashes _sometimes_, usually if he app is busy - ie, I'm moving
>>> between screens (which triggers calculations) etc. But sometimes just
>>> if it's sitting idle. I've tried putting the logging into a
>>> InvokeOnMainThread, but with the same result.
>>>
>>> I wasn't using TF before, but I've not had the Json problem in
>>> previous versions (I have a lot of production code out there which is
>>> working doing this). That said, I wasn't using Tasks before (I was
>>> using the threadpool), which may also be it!
>>>
>>> Any ideas? did this change after 5.2.4 (I'm on 5.2.8 I think at the
>>> moment)
>>>
>>> I have a semi-stacktrace thing, but it has almost no actual info in
>>> it. I'm going to try a debug build tonight, and see if I can get more
>>> info out. console just shows that the app segfaulted (error 11 I
>>> think??)
>>>
>>>  Outside of that, everything is exceptionally delicious with iOS5, the
>>> appearance API's, and the Task API's :)
>>>
>>> N
>>>
>>> --
>>> Nic Wise
>>> t.  +44 7788 592 806 | @fastchicken | http://www.linkedin.com/in/nicwise
>>> b. http://www.fastchicken.co.nz/
>>>
>>> Nearest Bus: find when the next bus is coming to your stop.
>>> http://goo.gl/Vcz1p
>>> mobileAgent (for FreeAgent): get your accounts in your pocket.
>>> http://goo.gl/IuBU
>>> Trip Wallet: Keep track of your budget on the go: http://goo.gl/ePhKa
>>> London Bike App: Find the nearest Boris Bike, and get riding!
>>> http://goo.gl/Icp2
>>> _______________________________________________
>>> MonoTouch mailing list
>>> MonoTouch at lists.ximian.com
>>> http://lists.ximian.com/mailman/listinfo/monotouch
>>
>>
>
>
>
> --
> Nic Wise
> t.  +44 7788 592 806 | @fastchicken | http://www.linkedin.com/in/nicwise
> b. http://www.fastchicken.co.nz/
>
> Nearest Bus: find when the next bus is coming to your stop. http://goo.gl/Vcz1p
> mobileAgent (for FreeAgent): get your accounts in your pocket.
> http://goo.gl/IuBU
> Trip Wallet: Keep track of your budget on the go: http://goo.gl/ePhKa
> London Bike App: Find the nearest Boris Bike, and get riding! http://goo.gl/Icp2



-- 
Nic Wise
t.  +44 7788 592 806 | @fastchicken | http://www.linkedin.com/in/nicwise
b. http://www.fastchicken.co.nz/

Nearest Bus: find when the next bus is coming to your stop. http://goo.gl/Vcz1p
mobileAgent (for FreeAgent): get your accounts in your pocket.
http://goo.gl/IuBU
Trip Wallet: Keep track of your budget on the go: http://goo.gl/ePhKa
London Bike App: Find the nearest Boris Bike, and get riding! http://goo.gl/Icp2