Qt Plugins causing memory problems?

[gavinmagnus]

Architecture of my project looks as follows:

Main project, that is compiled as stand-alone application:

TEMPLATE = app

Sub projects, that are compiled as libraries:

TEMPLATE = lib

Plugins, that are compiled as Qt Plugins:

CONFIG += plugin
TEMPLATE = lib

Common directory, that contains libs used by more than one element, f.e. all sub projects and one plugin.

TEMPLATE = lib

---
Main project accesses Sub projects as a libraries:

INCLUDEPATH += \

$$(SUB)/my_sub_pro1/lib \

DEPENDPATH += \

$$(SUB)/my_sub_pro1/lib \

LIBS += \

-L$$(BUILD_SUB)/lib -lmy_sub_pro1\

Sub projects access plugins by using standard QPluginLoader. I'm checking all files in my plugin build directory and cast them:

QPluginLoader loader(pluginsDir.absoluteFilePath(fileName));
QObject *plugin = loader.instance();
myPluginInterface* plugin = qobject_cast< myPluginInterface* > (plugin);

QPluginLoader loader(pluginsDir.absoluteFilePath(fileName));
QObject *plugin = loader.instance();
myPluginInterface* plugin = qobject_cast< myPluginInterface* > (plugin);

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Any Main, Sub or plugin project that would like to use commons, is simply including them:

SOURCES += \

$$(COMMON)/common/calc.cpp

HEADERS += \

$$(COMMON)/common/calc.h

---

I've got problem with my application crashing without reason on closing: It crashes in malloc.c: malloc_consolidate (Full stack below). This makes it incredibly hard to debug. I used Valgrind till the moment it doesn't show any memory leaks, but the problem persists. My friend once told me, that he had some problems while using static variables in plugins. I think he was right, because when I got rid of them me application is now crashing less often. I also had a small problem after adding a constexpr, but after some time the problem disappeared and I couldn't reproduce it.

I cannot possibly paste all the code that might be causing problems. However I would like to sincerely ask for any idea that might cause problems on destruction in architecture that I'm using. I will be really thankful for any idea on what to check or what could be potential problems while creating program that is using a dynamic library that is using plugins. I couldn't find any similar topic on problems with Qt Plugins.

It is worth to mention that crash only occurs on closing, and all destructors are called properly. What is more, when I created a stand-alone program that simply uses one Subprogram with plugins it works perfectly. Additionally if I use MainProgram to call any Subprogram without plugins it also works effortlessly. I'm using Qt 5.3.2.

Stack view on crash:

0	malloc_consolidate	malloc.c	5206	
1	_int_free	malloc.c	5079	
2	QArrayData::deallocate		130	
3	QTypedArrayData<int>::deallocate		234	
4	QVector<int>::freeData		473	
5	QVector<int>::~QVector		76	
6	QRegExpEngine::~QRegExpEngine		1356	
7	QCache<QRegExpEngineKey, QRegExpEngine>::clear		126	
8	QCache<QRegExpEngineKey, QRegExpEngine>::~QCache		95	
9	(anonymous namespace)::Q_QGS_globalEngineCache::Holder::~Holder		3825	
10	__cxa_finalize	cxa_finalize.c	56	
11	__do_global_dtors_aux	/opt/Qt-5.3.2/lib/libQt5Core.so.5		
12	??			
13	_dl_fini	dl-fini.c	254

0	malloc_consolidate	malloc.c	5206	
1	_int_free	malloc.c	5079	
2	QArrayData::deallocate		130	
3	QTypedArrayData<int>::deallocate		234	
4	QVector<int>::freeData		473	
5	QVector<int>::~QVector		76	
6	QRegExpEngine::~QRegExpEngine		1356	
7	QCache<QRegExpEngineKey, QRegExpEngine>::clear		126	
8	QCache<QRegExpEngineKey, QRegExpEngine>::~QCache		95	
9	(anonymous namespace)::Q_QGS_globalEngineCache::Holder::~Holder		3825	
10	__cxa_finalize	cxa_finalize.c	56	
11	__do_global_dtors_aux	/opt/Qt-5.3.2/lib/libQt5Core.so.5		
12	??			
13	_dl_fini	dl-fini.c	254

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