[Interest] reference counting

[Sean Harmer]

On Sunday 16 November 2014 19:02:19 René J.V. Bertin wrote:
> On Sunday November 16 2014 18:47:34 Giuseppe D'Angelo wrote:
> > Most of the value classes are implicitly shared:
> > 
> > http://qt-project.org/doc/qt-5/implicit-sharing.html
> 
> Yes, I saw that doc (also in Qt4). What kind of sharing does this refer to -
> across threads and/or only across owners in a same thread? ObjC's reference
> counting basically determines the lifetime of an object (and prevents the
> need for a "deleteLater" operator).

QSharedPointer?

> But the main thing I'm curious about:
> is this implicit sharing mechanism thread safe and if so, do you (thus) use
> some kind of interlocked increment/decrement of the reference counter?

An atomic integer is used. See for e.g. QVector which uses QArrayData which in 
turn uses QtPrivate::RefCount which in turn uses QBasicAtomicInt.

Cheers,

Sean
--
Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
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