[Development] Qt LTS & C++11 plans

[Knoll Lars]

Hi,

I’ve went through the plans that we now have for Qt 5.6 and think that we
need to slightly adjust our plans to deprecate certain compilers and move
over to C++11.

We are currently around 6 weeks away from the 5.6 feature freeze, and
currently the dev branch is still nicely compiling in C++98 mode, and we
still test all the older compilers (and platforms such as WEC7) in the CI
system. I do not see us gaining much from throwing this support now out a
couple of weeks before the feature freeze. On the opposite, I’m afraid it
would lead to us trying to rush some new code at the last minute and not
give us proper time to test before the freeze.

After discussing with a couple of different people, here’s the updated
proposal for 5.6 and onwards.

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)

This would mean that we’d simply remove the older compilers and platforms
from the dev branch of the CI system a few weeks later than originally
planned. From an R&D perspective it means we can start fully relying on
the new compiler baseline from the beginning of August (once we branched
5.6). So it’s a rather small delay from an R&D perspective, but it’ll give
us a broader baseline of supported platforms and compilers for our LTS
release. It’s basically what we wanted to do for 5.5, but couldn’t because
the CI system wasn’t yet in place.

Cheers,
Lars