[Development] Qt LTS & C++11 plans

[Olivier Goffart]

On Tuesday 23. June 2015 10:17:40 Knoll Lars wrote:
> Qt 5.6:
> 
> * We make 5.6 a long term supported release
> * We still support C++98 compilers in this release (for the last time),
> i.e. We keep the 5.5 compiler baseline
> * WEC7 will be still supported
> * QNX 6.5 is not supported anymore
> * Qt Quick1 and Qt WebKit are not part of the release (but we test that
> the sources compile against 5.6)
> * We keep Qt Script for this release, it’ll be gone in 5.7 as well
> 
> Qt 5.7:
> 
> * New compiler baseline with gcc 4.7 and VC++ 2012
> * Enable and use the C++11 features supported by these compilers
> unconditionally
> * WEC7 not supported anymore, WEC2013 supported
> * Probably remove support for older Android, Mac and Linux versions as
> well (to be discussed)

+1

There is another point we need to decide on (for Qt 5.7), is whether or not we 
relax the policy not to use the standard library in our ABI.

Can we have function that takes or return std::function, std::tuple, 
std::unique_ptr, std::vector?

Currently we don't allow it, and this makes it possible to change the 
underlying standard library without breaking binary compatibility. (Qt can 
link to one standard library, and the application to another. Or, if they use 
inline namespace, the namespace can change provided that both old and new 
symbols are still in the library.)

However, it is questionable if even this works. We already rely on the 
standard library ABI in QException. And most users will have to recompile 
everything if they want to change standard library anyway.

We currently do not have a general purpose std::function (there is 
QtPrivate::QSlotObjectBase, but it is not as good as std::function 
implementations).
I believe it is better to use std::function than trying to reinvent our own.

So should we allow standard library types in our ABI?
Nobody seemed to be opposed in the "Notes from Modern C++ session" thread.

-- 
Olivier 

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