Qt5 switching qreal from float to double on arm*

[Lisandro Damián Nicanor Pérez Meyer]

On Wednesday 06 November 2013 17:40:11 Pino Toscano wrote:
> In data sabato 2 novembre 2013 15:29:05, Lisandro Damián Nicanor Pérez
> 
> Meyer ha scritto:
> > Hi! Starting from Qt 5.2.0 (most probably from rc1 and definitely not
> > from beta1 currently in experimental) Qt5 will switch qreal from
> > float to double on arm*.
> 
> Did upstream bump the SONAME of QtCore5 and any other qt5 library
> because of this?

No. And I also agree this should have been done from Qt5's first version, but 
that didn't happened.

> > Of course we are still on time to discuss this, and this is the reason
> > of this mail. What do you think WRT the above changes?
> 
> This will basically break the ABI of basically all the Qt5 libraries on
> those architectures. Unless upstream already managed the SONAME bump
> already, it would imply that Debian has to maintain it on its own...
> are you sure these changes are worth the pain they cause?

Depends on how you see it. Only three apps curently B-D on Qt5 in the archive. 
Yes, this means that a binary incompatible change will need to occur without a 
soname bump in (so far) one arch. But I *think* this can be managed quite 
easily with three armhf-binNMUs.

Of course, I might be missing something else (as I did wrt LSB/binary 
compatibilty with other distros), that's why I asked here before doing 
anything.

> > On the other hand, if the above change is kept, symbols for Qt5 on
> > armhf managed with pkg-kde-tools' symbolshelper will need an explicit
> > double for armhf instead of using qreal's subst. This is because on
> > Qt4 qreal will be kept as float.
> 
> This is another issue, i.e. pkgkde-symbolshelper not being able to
> distinguish version of qt for substitutions.

I agree here.

> > We have the option to keep some archs in float by passing a
> > compilation parameter. I've done so for armel and sh4, so only armhf
> > will switch to double.
> 
> My option goes on keeping the status quo of qreal as it was, on
> architectures that managed to build qtbase-opensource-src already.

Thanks for your opinion and time :)

I will ask in Qt's dev list to see if other distros are going to keep the ABI 
or not for this cases.


Kinds regards, Lisandro.

-- 

Lisandro Damián Nicanor Pérez Meyer
http://perezmeyer.com.ar/
http://perezmeyer.blogspot.com/
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