[Development] qHash / QHash changes

Thiago Macieira thiago.macieira at intel.com
Mon Mar 19 11:24:37 CET 2012


On segunda-feira, 19 de março de 2012 11.17.29, André Somers wrote:
> Op 19-3-2012 10:42, Thiago Macieira schreef:
> > They shouldn't rely on that at all. The documentation of QHash says
> > that it produces an arbitrary but stable[1] order.
> > 
> > [1] note that the order is stable. Two hashing tables with the same
> > elements must produce the same order.
> 
> If I understood Giuseppe correctly, the meaning of 'stable' will be
> limited to those hashes that have been initialized with the same seed,
> which by default is the case for hashes within the same process, but not
> for hashes created in different processes or in different runs of the
> application.

Oh.

I'm not sure we want that then. It might be a security feature, but it's WAY 
too late to add that to Qt 5.

It breaks the property of comparing QHashes item by item. That's probably the 
property I relied on in the QtDBus unit tests in question.

The seed could be calculated once per process, instead.
-- 
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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