[Development] Possible binary compatibility problem in a future Qt version

[Thiago Macieira]

On segunda-feira, 11 de junho de 2012 10.33.13, Jedrzej Nowacki wrote:
> > A type's information can only be modified by adding new traits.
> 
> Keep in mind that by introducing a new trait you are actually changing
> existing state. Imagine that we do not have movable flag. So by default
> everything is not movable. Then we introduce it, suddenly some types
> virtually change movable attribute. In this case it 98% safe, because
> default value is always valid.

Which is why I said this below. See (b):

> > (...)
> > I'd suggest that any automatic flags can only exist if they are either:
> > 
> > a) present in Qt 5.0
> > b) completely forwards and backwards compatible for all uses (something
> > that might be hard to prove)
> 
> a) And bug-less... such flag can not be fixed without recompiling.
> b) Such requirement makes the flag completely useless. I hope that you mean
> forward compatibility, which means that an app compiled with an older Qt
> version would work correctly with a newer Qt version.

No, I mean that you cannot add an automatic flag that changes the behaviour of 
existing code.

-- 
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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