A maliit-framework segfault with Qt 5.4.1

[Timo Jyrinki]

Crashing at QV4::ExecutionContext::setProperty()

See https://wiki.ubuntu.com/Touch/QtTesting for information on how to upgrade to silo 012 with Qt 5.4.1.

All necessary Qt private headers users _should_ be rebuilt, per the latest knowledge. However, compared to 5.3.2 -> 5.4.0 transition, the following packages were found not to depend on qtbase-abi-5-4-0 / qtdeclarative-abi-5-4-0 so not rebuilt this time: oxide-qt qtubuntu-sensors qtvideo-node webbrowser-app ubuntu-html5-theme ubuntu-system-settings-online-accounts (some are recent known dropouts, some may have been without private symbol usage also during 5.3.0 -> 5.3.2 transition). If in doubt, https://launchpad.net/~canonical-qt5-edgers/+archive/qt5-beta2/+packages has rebuilds of a lot of packages for the new testing reasons (unit tests get run etc).

All Qt 5.4.1 bugs https://bugs.launchpad.net/bugs/+bugs?field.tag=qt5.4

[Michael Sheldon (michael-sheldon)]

Looks like the ubuntu-keyboard package should be added to that silo and rebuilt against 5.4.1. After doing so locally the crashes no longer occur.

[Albert Astals Cid (aacid)]

I just tried the ppa 12 that just gained a rebuilt ubuntu-keyboard package and maliit-server still seems to be crashing here.

[Michael Sheldon (michael-sheldon)]

Yep, I can confirm that the crash stopping after recompiling now appears to have been coincidental as I'm now able to reproduce the issue again after recreating the conditions with a clean image.

[Michael Sheldon (michael-sheldon)]

Looks like this was caused by the QML cache not having been cleared. This normally happens during image upgrades, but since the Qt 5.4.1 upgrade is just done via apt-get this doesn't happen. The crashes stop as soon as you delete ~/.cache/QML/Apps/maliit-server (or alternatively if you delete this before restarting after the upgrade the crash never happens). For completeness you probably actually want to delete the whole ~/.cache/QML/Apps directory when testing this silo or you might hit similar problems in other apps.

[Albert Astals Cid (aacid)]

Can confirm that erasing the cache fixes the crash.

I thought we already had a cache deletion mechanism in place. Ricardo?

[Albert Astals Cid (aacid)]

So the deletion mechanism is in image updates and not in apt-get update.

Guessing we can just put this as invalid then?

[Timo Jyrinki (timo-jyrinki)]

This is at least a good explanation for the problem, even though it ended up eating time :( The worse explanation would have been the need to rebuild ubuntu-keyboard, since there was no indication it should be needed in the symbols usage.