[Development] Help reviewing my own changes to QSharedPointer

[Thiago Macieira]

On quarta-feira, 6 de junho de 2012 21.56.16, lars.knoll at nokia.com wrote:
> >https://codereview.qt-project.org/26981-Optimisedeletion
> 
> I might be wrong (getting tired), but I think this reintroduces the
> problem with forward declared pointers that the first patch fixes.

It's a different solution.

The Qt 4 solution for this was to return false from a virtual function (the 
default implementation), which would require the caller to perform the 
deletion. The code was like this:

	if (!d->destroy())
		delete value;

This function was called from deref(), which meant that where a reference 
could be dropped also required a full definition of the class.

The new optimisation does not introduce "delete value" into the reference-
dropping code path. That is still:

	d->destroy()
which does:
        void destroy() { destroyer(this); }
	(destroyer is a function pointer)

The optimisation simply changes what the pointed function does. Wiithout it, 
it will call another stored function pointer. With it, it will call delete 
directly.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center
     Intel Sweden AB - Registration Number: 556189-6027
     Knarrarnäsgatan 15, 164 40 Kista, Stockholm, Sweden
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