To C++11 or not?

[Kevin Funk]

On Friday, 30 December 2016 15:29:52 CET Kevin Funk wrote:
> On Friday, 30 December 2016 15:25:56 CET David Faure wrote:
> > On vendredi 30 décembre 2016 12:56:09 CET Albert Astals Cid wrote:
> > > El divendres, 30 de desembre de 2016, a les 12:24:38 CET, Luigi Toscano
> > > va
> > > 
> > > escriure:
> > > > Il 30 dicembre 2016 10:30:22 CET, Kevin Funk <kfunk at kde.org> ha 
scritto:
> > > > >Following-up on this thread, since I saw some more discussion about
> > > > >C++11
> > > > >
> > > > >usage in this RR:
> > > > >  https://git.reviewboard.kde.org/r/129724/
> > > > >
> > > > >Let's put this into some concrete actions, finally. I think we all
> > > > >agree
> > > > >nullptr & override are probably the most apparent issues (since
> > > > >compilers
> > > > >started to warn about both), and *having* 'override' is actually
> > > > >super
> > > > >useful
> > > > >for preventing programmer faults.
> > > > >
> > > > >Let's just speak about allowing nullptr & override, allowing the full
> > > > >set of C
> > > > >++11 is *not* feasible. Reason: Lot's of C++11 feature are only
> > > > >available only
> > > > >in MSVC2015, so we'd just be able to support the latest VS. See [2].
> > > > >
> > > > >Looking at [1] I still see we list GCC 4.5 as minimum requirement.
> > > > >That's
> > > > >pretty ancient. 4.5.1 got released Jul 2010 [3]
> > > > >
> > > > >If we raise that to GCC 4.6 (4.6.0 being released Mar 2011), we can
> > > > >use
> > > > >
> > > > >'nullptr' unconditionally. ktexteditor already did that in public
> > > > >headers for
> > > > >quite some time -- no-one complained.
> > > > >
> > > > >If we raise that to GCC 4.7 (4.7.0 being released Mar 2012), we can
> > > > >use
> > > > >
> > > > >'override' unconditionally *.
> > > > >
> > > > >We already use MSVC2012 as min VS dep, this version has full nullptr
> > > > >&
> > > > >override support. I don't see anyone using MSVC2010 for compiling KF5
> > > > >to be
> > > > >honest...
> > > > >
> > > > >Proposal for [1]:
> > > > >- Raise min GCC version to 4.7
> > > > >- Allow to use override unconditionally
> > > > >- Allow to use nullptr unconditonally
> > > > >
> > > > >ACK?
> > > > >
> > > > >
> > > > >PS: I can do the work, I can script the refactoring with clang-tidy.
> > > > >
> > > > >Let's move forward please.
> > > > 
> > > > Hi, this is a really good analysis (also for future reference). In
> > > > order
> > > > to
> > > > complete it, given that the original idea was "follow Qt's
> > > > requirement",
> > > > and that we increased in time the required version of Qt, what is the
> > > > current status regarding compilers and Qt?
> > > 
> > > Our min requirement is Qt 5.5 which according to
> > > http://doc.qt.io/qt-5/supported-platforms-and-configurations.html
> > > compiles with GCC 4.6 (Qt 5.6 has the same supported GCC it seems)
> > 
> > Then that's a no-brainer, we can require gcc 4.6 too.
> > 
> > Qt 5.9 (currently "git dev branch") uses override rather than
> > Q_DECL_OVERRIDE, but we're far from requiring 5.9.
> > 
> > This leads to a different proposal:
> > - Raise min GCC version to 4.6
> > - Allow to use nullptr unconditionally
> > - Use Q_DECL_OVERRIDE.
> 
> +1 from my side. I didn't know that we wanted to follow the Qt version's
> minimum compiler requirements. Makes sense.
> 
> Thanks for chiming in!
> 
> I'll port KF5 (at least the (public) headers) to nullptr if this proposal is
> accepted.

Didn't see any objections thus I think we're good on the 'let's use nullptr' 
side.

Here's my patch (just showing an excerpt): 
  https://phabricator.kde.org/D3987

Cheers,
Kevin

> Cheers,
> Kevin
> 
> > I fully agree that "having 'override' is actually super useful for
> > preventing programmer faults", but that also works if it's spelled out
> > Q_DECL_OVERRIDE and only ineffective for people *using* frameworks on an
> > older system with gcc 4.6. It's still effective for all of us who are
> > working on frameworks, which is where the benefit of "override" is.
> > 
> > BTW just to get a taste of the real world, I'm working with a customer
> > right now who is using Qt 5 and gcc 4.4 in order for their binaries to
> > work on the largest possible number of Linux distros out there (glibc
> > version). They are not using KDE Frameworks, obviously, but this is just
> > to point out that there are companies using older gcc versions still,
> > this is not just hypothetical.
> > 
> > Funny that I kept saying "MSVC is what's holding us back" when in fact
> > it's
> > GCC that is holding us back ;)
> > 
> > 
> > PS: I disagree with the "nobody complained" approach. Many people will
> > simply choose another library than complain about one library not being
> > suited to their constraints (one of which being the supported compiler).


-- 
Kevin Funk | kfunk at kde.org | http://kfunk.org
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