[Development] Question about QCoreApplicationData::*_libpaths

Marc Mutz marc.mutz at kdab.com
Tue Jan 19 16:09:48 CET 2016

On Tuesday 19 January 2016 14:33:46 Giuseppe D'Angelo wrote:
> On Tue, Jan 19, 2016 at 3:07 PM, Marc Mutz <marc.mutz at kdab.com> wrote:
> > I'd aggregate the std container instead of inheriting it, but yes, that's
> > a good idea. I just wrote a mail suggesting essentially the same, only
> > slower.
> > But I'd have nothing against going all-in, either.
> We can't "suddenly" break CoW, though. Who's going to review the millions
> of lines of code where copies where happily taken assuming they were cheap?

Who's reviewing the millions of lines of code where hidden detaches are 
happily incurred even though they are not cheap?

I'd say that if you took copies in a tight loop, you'll notice and the profiler 
will find it for you. And the rest don't matter, or they will be found by 

I doubt many people actively use the fact that Qt containers are cheap to 
copy. But yes, Qt API needs to be reviewed with an eye towards this. Then 
again, Non-Qt C++ would be horribly slow if copying containers was so 
prohibitly expensive.


Marc Mutz <marc.mutz at kdab.com> | Senior Software Engineer
KDAB (Deutschland) GmbH & Co.KG, a KDAB Group Company
Tel: +49-30-521325470
KDAB - The Qt Experts

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