heads up - Qt qreal difference on ARM

[Richard W.M. Jones]

On Thu, Aug 01, 2013 at 10:49:12PM -0600, Orion Poplawski wrote:
> http://doc.qt.digia.com/4.6/qtglobal.html#qreal-typedef
> 
> typedef qreal
> 
> Typedef for double on all platforms except for those using CPUs with
> ARM architectures. On ARM-based platforms, qreal is a typedef for
> float for performance reasons.
[...]
> Is double really that much slower on arm?

According to:

https://developer.android.com/training/articles/perf-tips.html#avoidfloat

there's no difference on modern hardware.  (Note I didn't verify this.)

Judging by a google search for "qreal" "float" "arm" this difference
causes endless problems.  I even found a Fedora build bug related to it.

However it's a matter for upstream to fix it.  Not something we could
carry around only in Fedora IMHO.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top