[Interest] Unknown crashes with Qt, iOS and iPad Air

[Robert Iakobashvili]

On Mon, Apr 20, 2015 at 11:36 AM, Nuno Santos <nunosantos at imaginando.pt> wrote:
>
> My app is mostly a remote controller. It connect itself via QTcpSocket to a software utility on the host computer side and exchanges information with it. It has a lot of GUI and it’s currently memory hungry. I receive memory warnings easily and I still couldn’t find a way of lowering memory usage.
>
> The version that is currently on the store is reporting crashes very similar to the one in the image attached. Since it is not in any point of my source code, I don’t have a clue of what it is.
>
> The place point before pointing to LK is the CFNetwork module. Could this indicate that the crash was caused during a network callback?


I'm not so familiar to QTcpSockets and its callbacks.
Hope, that other people using it could comment.

Some general advises:
- look into various network error cases;
- check that you stop all timers and networking activity
  when going to background.

>
> Is your application memory hungry?
> Are you treating memory notification?
>
> How am I supposed to treat memory notifications in Qt? One of the current problems is that i’m currently spending a lot of memory, specially due to Qml interfaces. How can I know how much a Qml element is spending memory? I couldn’t find that in Qml profiler yet.


iOS expects your app to release memory on memory notifications.

iOS devices are particularly memory sensitive. Modern devices have 1
GB of memory
whereas old like iPad-2 have only 512 MB of RAM.

You can find by search that a general recommendation is not to take more than
10% of RAM, otherwise expect memory notifications.

So, you may wish to fit into up to 100 MB, and for old devices into up
to 50 MB regular usage.
Therefore, welcome to the club and re-work your memory usage, sorry.

For memory-hungry apps, widgets could be sometimes the only option
for iOS devices, at least in meanwhile.

Sorry, I'm not familiar with QML profiler,
but hope some other people could comment.

Take care,
Robert