[Development] Deprecated functions / procedure of removal in Qt6?

[Elvis Stansvik]

Den mån 22 okt. 2018 kl 00:14 skrev Giuseppe D'Angelo via Development
<development at qt-project.org>:
>
> Hi,
>
> Il 21/10/18 19:59, Christian Ehrlicher ha scritto:
> > there are a lot of deprecated functions in qtbase which are only marked
> > as deprecated/obsolete in the documentation but don't have a
> > Q_DECL_DEPRECATED. Most of them were deprecated in the pre Qt5-era.
> > What's the 'correct' way to make sure they can be removed with Qt6? Must
> > they marked as QT_DEPRECATED_SINCE(5,x) or is the comment in the
> > documentation enough?
>
> The documentation comment is enough for us to justify the removal -- in
> other words, "formally", we have informed the user to move away, and the
> rule is that we can drop deprecated functions any time we want to break
> source compatibility.
>
>
> However, it's nowhere enough to
>
> 1) make users _aware_ of the fact that they're using deprecated APIs;
> 2) make us _remember_ to remove those functions when we have the chance
> (like in Qt 6).
>
> Thus, adding deprecation warnings is definitely the right thing to do:
> users get the deprecation warnings (*), and we have an easy way to find
> and drop all those functions.
>
> The other ways to achieve 2) at the moment are:
>
> * If possible, all the code to be killed in Qt 6 should already be
> protected via
>
> >  #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
>
>
> * Add some comment in the source code like
>
> // ### Qt 6: remove this
>
>
> Both ways are more general and apply to functions we can't just
> deprecate or remove (f.i., marking an overload to be merged with another
> one via a default argument, getting rid of useless special member
> function declarations, and the like).
>
> Of course, simply leaving a comment requires us to remember find those
> usages and act on those, and the code is still full of such TODOs for Qt
> 5...
>
>
> (*) I don't like that the deprecation warnings are opt-in and not
> opt-out. People deserve to know as soon as possible that they're using
> deprecated functionality, rather than have a gigantic unpleasant
> surprise ("you're using lots of deprecated stuff that got removed!")
> when Qt 6 comes.

+1 for opt-out from a user.

I had forgotten to add this to the build of our application. Will be
interesting to see what it'll turn up :p

Elvis

>
>
> My 2 c,
> --
> Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
> KDAB (France) S.A.S., a KDAB Group company
> Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
> KDAB - The Qt, C++ and OpenGL Experts
>
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