[Development] Problem loading plugins with gcc 4.9.2

Sergio Martins sergio.martins at kdab.com
Tue Mar 3 23:14:55 CET 2015

On Tuesday, March 03, 2015 11:45:49 Thiago Macieira wrote:
> On Tuesday 03 March 2015 13:55:29 Sergio Martins wrote:
> > Hi,
> > 
> > So that you don't waste time pulling your hair out: plugin loading is
> > broken with gcc 4.9.2
> > 
> > There's some clash between global static QFactoryLoader instances.
> > Reproduced on Archlinux (and on Fedora by jpnurmi).
> Please explain the problem.

The problem is that:

(gdb) bt
#0  (anonymous namespace)::Q_QGS_loader::innerFunction () at 

#1  0x00007ffff6ff2250 in QGlobalStatic<QFactoryLoader, (anonymous 
namespace)::Q_QGS_loader::innerFunction(), (anonymous 
namespace)::Q_QGS_loader::guard>::operator()() (this=0x7ffff75d54f0 <_ZL6loader>)
    at ../../include/QtCore/../../src/corelib/global/qglobalstatic.h:129

#2  0x00007ffff70020ab in QPlatformIntegrationFactory::create (platform=..., 
paramList=..., argc=@0x7fffffffdd1c: 1, argv=0x7fffffffde28, platformPluginPath=...) at 

#3  0x00007ffff700db47 in init_platform (pluginArgument=..., platformPluginPath=..., 
platformThemeName=..., argc=@0x7fffffffdd1c: 1, argv=0x7fffffffde28) at 

#4  0x00007ffff700ed7a in QGuiApplicationPrivate::createPlatformIntegration 
(this=0x601a80) at kernel/qguiapplication.cpp:1165

In frame #2, we do loader(), which should create an instance of the "/platforms" 
QFactoryLoader, but instead, it calls innerFunction() of a global static of another translation 
unit (QFactoryLoader of "/accessible" plugins).

A simple fix is to use "loader" instead of "loader()"

SĂ©rgio Martins | sergio.martins at kdab.com | Software Engineer
Klarälvdalens Datakonsult AB, a KDAB Group company
Tel. Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
KDAB - Qt Experts - Platform-independent software solutions
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