Segmentation Fault while using QQueue::enqueue()

You're corrupting your QQueue with your initialization of the string array. For those who (like me) are having trouble navigating your Sources/Branches/SubRepositories...your declaration of QtLogger looks like this:

class LIBQTLOGGER_EXPORT QtLogger
{
public:
    typedef enum {
        LL_EROR,
        LL_WARNING,
        LL_LOG,
        LL_DEBUG,

        LL_COUNT
    } LOG_LEVEL;

public:
    QtLogger();
    ~QtLogger();

public:
    void foo( void* );

    void log( LOG_LEVEL, QString );

protected:
    LOG_LEVEL currentLevel;
    QString ll_string[ LL_COUNT ];

    QQueue< QString > messageQueue;
    QMutex mqMutex;
};

And then your constructor looks like this:

QtLogger::QtLogger()
    : currentLevel( LL_DEBUG )
{
#if ENABLE_LOGGER_LOGGING
    std::clog << __PRETTY_FUNCTION__ << std::endl;
#endif

    ll_string[ LL_EROR      ].sprintf( "ERROR" );
    ll_string[ LL_WARNING   ].sprintf( "WARN " );
    ll_string[ LL_LOG       ].sprintf( "LOG  " );
    ll_string[ LL_DEBUG     ].sprintf( "DEBUG" );

    ll_string[ LL_COUNT     ].sprintf( "     " );
}

LL_EROR is 0, LL_COUNT is 4. (Sidenote: That word is spelled "ERROR", so your string is the correct bit.) Anyway...your declaration is effectively QString ll_string[4]; into which you are putting 5 strings and corrupting the subsequent member variable.

Why you put that empty string in there in the first place is a bit of a mystery to me... (!) But either way, vector classes are pretty light weight in the scheme of things rather than raw arrays, and often provide more checking on bounds for common operations. Use QVector (or whatever) in the future and it will be easier to catch this class of bug:

http://qt-project.org/doc/qt-4.8/qvector.html

In short, this has nothing to do with shared-libraries. Next time, try building everything into a single executable before assuming that's relevant! :-)