Hello After the alpha, I'd like to dismantle the QtPlatformSupport library and fix it properly. It should be broken up into smaller libraries or back into .pri files to be included.
I know this is not going to be a popular change, but please bear with me on the explanation: Due to a mistake in the Qt buildsystem, the -Wl,--no-undefined is not used in plugin builds. This has led many plugins to be linked with undefined symbols because the necessary libraries were missing. In turn, that leads to surprising errors at runtime, like the application reporting that no platform plugins are present when libqxcb.so is clearly present. QtPlatformSupport was initially a bunch of .pri files that were included from plugins and caused code to be built and linked into the plugins. The mistake in forgetting the dependent libraries was already present in those .pri files. Then QtPlatformSupport was made into a convenience static lib (that is, a static library linked to a dynamic Qt, meant to be linked into another dynamic lib or plugin). Unlike any other convenience library out there, QtPlatformSupport is not meant to be used as a whole: plugins only need part of it. When I re-added support for -Wl,--no-undefined, I noticed that many plugins failed to link because the dependent libs were missing. So I proceeded to add those libs. Either way, with those libs being listed in .pri files inside QtPlatformSupport, all plugins linking to QtPlatformSupport link to those libs. That includes stupid things like the directfb plugin linking to the X11 libs. To make matters worse, a well-intentioned change (change 18023[1]) removed the libs from the .pri files. That, of course, meant that the plugins would fail to load unless the libs are listed in the plugins' .pro files. That change was made. However, the plugins STILL DON'T LINK with -Wl,--no-undefined. The reason for that is because QtPlatformSupport is a static library: the order of libraries listed in the command-line is relevant. qmake does the right thing when the libraries are listed as dependent in the libQtPlatformSupport.prl file. I asked ossi on IRC and we cannot find a way to set the library order to the right one, unless the libs are listed in the .pri .LIBS. Conclusion: since the libs must be listed when creating the static lib, the only way to avoid having DirectFB link to X11 is to break up QtPlatformSupport into smaller libs. This will be hard to do with qmake, so the easier way out is to remove the .a altogether and use .pri files only. That requires moving the Wayland platform plugin back into qtbase. [1] https://codereview.qt-project.org/18023 -- Thiago Macieira - thiago.macieira (AT) intel.com Software Architect - Intel Open Source Technology Center Intel Sweden AB - Registration Number: 556189-6027 Knarrarnäsgatan 15, 164 40 Kista, Stockholm, Sweden
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