Can Q_GLOBAL_STATIC replace KStaticDelete ?

Matthias Kretz kretz at
Thu Jan 18 12:01:30 GMT 2007

On Thursday 18 January 2007 00:48, Thiago Macieira wrote:
> Matthias Kretz wrote:
> >changes:
> >- removed K_GLOBAL_STATIC_WITH_ARGS in favor of putting all ctor and
> > dtor calls in the KGlobalStatic class so that singletons can declare
> > there ctor and dtor private/protected and make
> > KGlobalStatic<SingletonClass> a friend.
> > - replaced
> > q_atomic_test_and_set_ptr with QBasicAtomicPointer::testAndSet
> Problem with your patch:
> You're using an atomic test-and-set to make the object assignment
> thread-safe, but your KGlobal::addGlobalStatic isn't thread-safe.

Right. Not completely thought out... :(

> Either you make it fully thread-safe by adding a mutex protection around
> _globalStatics or you can drop thread safety and drop the QAtomic usage.

/me leans towards dropping thread safety for K_GLOBAL_STATIC. Use 
Q_GLOBAL_STATIC if you want thread safety or if we really shouldn't use 
Q_GLOBAL_STATIC like Simon wrote, create a K_GLOBAL_STATIC_THREADSAFE (or 

Dropping thread safety in K_GLOBAL_STATIC means that those statics may only be 
initialized in the main thread. But that's the same we were expecting from 
our KStaticDeleter deleted objects.

> If you add a mutex, you can drop QAtomic too, since you can protect the
> pointer assignment with the mutex. In the documentation, be sure to note
> that K_GLOBAL_STATIC will be slower than Q_GLOBAL_STATIC.
> Note: as an irony, the mutex must be Q_GLOBAL_STATIC :-)

Anybody thinks this would be a good idea?

> > - moved
> > public static variables of KGlobal into the .cpp file (making it
> > file-static) where possible
> Can you make another patch for that?

Yep, attached. Commit next monday? Or safe to commit now?

Matthias Kretz (Germany)                            <><
MatthiasKretz at, kretz at,
Matthias.Kretz at
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