[Development] Passing QSize, QPoint, QTime and other small structs by value

Marc Mutz marc.mutz at kdab.com
Fri Apr 7 17:28:51 CEST 2017

On Friday 07 April 2017 15:02:55 Lars Knoll wrote:
> There might be a little catch with regards to structs containing members
> that are 8 bytes in size (aka quint64). Are those getting passed in
> registers on 32bit ARM?

Forget register passing. To a first approximation, it does not matter. If you 
pass by cref, you surely force the value on the stack, anyway.

What pass-by-value has going for it is the elimination of memory, and with it 
the aliasing and const_cast problems that make the compiler's and developer's 
work hard.

Please watch Chandler Carruth's BoostCon 2013 presentation for the pov of 
compiler writers (https://www.youtube.com/watch?v=eR34r7HOU14) and Lawrence 
Crowl's CppCon 2014 presentation for the pov of a developer 


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, C++ and OpenGL Experts

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