[Development] Setters: Passing by value or const reference?

[Marc Mutz]

On Wednesday April 25 2012, Olivier Goffart wrote:
> > > We could implement a move setter (Foo::setText(QString&&)).  But that
> > > would
> > > mean  duplication, and it could not be inline (access to d_ptr) so
> > > binary incompatibility between Qt compiled with or without C++11.
> >
> > The rvalue overloads could only be used by a C++11 compiler, and it would
> > be natural for a C++11 app to require a C++11-compiled Qt.
>
> Not really...  
> On linux, if the dirstribution provides a qt compiled without C++11, i
> still want to be able to use C++11 it on my project.
> C++11 is still (unfortunatelly) not the default to build Qt on linux.

A late-entry data point:

libstdc++'s std::list is binary incompatible between -std=c++11 
and -std=c++98, because it adds a _M_size member.

It's the most stupid change I can imagine, but it apparently means that the 
GCC devs don't shoot for BC between C++11- and C++98-compiled code. I guess 
that, at least for GCC users, it might therefore actually be a boon if a Qt 
compiled in C++11 mode was incompatible with a Qt compiled in C++98 mode at, 
say, the linker level, lest they ran into such hidden BiC issues unawares.

Thanks,
Marc

-- 
Marc Mutz <marc.mutz at kdab.com> | Senior Software Engineer
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