Heads-up: Major issue in Qt 5.4 branch (will be 5.4.1)

[Albert Astals Cid]

El Dimecres, 3 de desembre de 2014, a les 00:10:46, Luca Beltrame va escriure:
> Hello,
> 
> TL; DR: beware of commit c91c05b056c769c3df0d7634aed7d9bf2c0e550d in qtbase,
> which is in the 5.4 branch and will be in Qt 5.4.1.
> 
> I spent most of this evening fighting a nasty bug that occurred with KF5
> apps. Basically most apps would crash instantly (the moment they displayed
> something) if launched from inside X11, but run perfectly if ran with
> DISPLAY=:0 foo.
> 
> Notice that it seems system-dependent: I tried to debug this with a couple
> of openSUSE KDE team members  and they were unable to reproduce.
> 
> Backtraces pointed at the Qt XCB plugin, but there weren't any recent
> changes there. Strace however indicated that
> libcomposeplatforminputcontextplugin.so was the last library loaded before
> the crash.
> 
> And it turned out that  c91c05b056c769c3df0d7634aed7d9bf2c0e550d touched
> exactly that plugin. Reverting it fixed all crashes.

The changeset of c91c05b056c769c3df0d7634aed7d9bf2c0e550d introduces a binary 
incompatible change to a private class, that is fine, but all the libraries 
depending on that class need to be rebuilt.

Are you sure you rebuilt everything that depends on that private header after 
installing the qt with that changeset?

Cheers,
  Albert

> 
> My level of skill with C++ is limited and I doubt I'd be able to make a Qt
> bug report with a Qt-only case. However I'm writing this to inform
> everyone, packagers included, to keep an eye on this. People with X11
> knowledge (Martin, Thomas? ;) might be able to help.