Tuukka Turunen

Support of Qt 5.6 LTS Ends in March 2019

Published Thursday November 29th, 2018
4 Comments on Support of Qt 5.6 LTS Ends in March 2019
Posted in Biz Circuit & Dev Loop, Qt, Releases

Support of Qt 5.6 LTS ends in March 2019. If you are still with Qt 5.6 LTS, update to Qt 5.9 LTS or Qt 5.12 LTS is recommended. If you can’t update, extended support is available for an additional fee after the standard support ends. 

Long term supported releases on Qt are supported for three years, thus the support for Qt 5.6 LTS ends in March 2019. Many users have already migrated to later releases, especially to Qt 5.9 LTS. Soon we have also Qt 5.12 LTS available, so those who have not yet switched to more recent versions of Qt are encouraged to do so now.

Qt 5.6 LTS was the first long-term supported Qt 5 release. During its lifetime it has received three patch releases and provided over 2000 bug fixes compared to the earlier Qt 5.5.1 release. Qt 5.6 LTS has been in the ‘Very strict’ phase already quite a while and after Qt 5.6.3 release there have been very little commits to the 5.6 branch. Mostly just the critical security fixes. Qt 5.6.3 will remain the last release of the series, as there will not be any more Qt 5.6 patch releases created.

Qt 5.6 LTS has been a good release, but the more recent long-term supported Qt releases are even better. For example Qt 5.9.7, the latest patch release of Qt 5.9 LTS, contains over 3000 bug fixes that are not part of Qt 5.6.3. Currently in ‘Strict’ phase, Qt 5.9 will still receive new patch releases bringing security updates and other important fixes. The soon-to-be-released Qt 5.12 LTS contains over 2000 bug fixes that are not part of Qt 5.9.7 release – and over 5000 bug fixes more than Qt 5.6.3 release. Of course there are also a lot of great new features as well as performance improvements provided by the new versions of Qt.

If you can not switch to c++11 compiler or use a platform no longer supported after Qt 5.6 LTS, Extended support is available. Especially if your Qt 5.6 LTS based application or device is actively maintained after March 2019, purchasing extended support is highly recommended. Extended support can be purchased both for Standard as well as Premium Support. To learn more about Extended support, please contact our Support team and ask about it.

More Information

We also have a couple of webinars lined up with additional information on the topic.

The one with the self-explanatory title “End of 5.6 Support – All You Need to Know” gives you an overview of what this change means to you, and details the different options you have.

The other webinar and focuses on licensing for versions 5.7 and later, since the obligations of LGPL/GPL v3 differ from what you had to comply with from Qt 5.6 LTS and earlier. Since this is very important, it will air in two two time zones EU and APACUS, so make sure to sign up and have your licensing questions answered live.

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Posted in Biz Circuit & Dev Loop, Qt, Releases


Massimo says:

Saying “Qt 5.12 LTS contains over 2000 bug fixes that are not part of Qt 5.9.7 release – and over 5000 bug fixes more than Qt 5.6.3 release” it’s basically like admitting that 5.9.7 has 2000 bugs and 5.6.3 has 5000 bugs…which is probably not what you meant.
I think you’re counting git commits, which include refactorings, documentation, cleanup, typos, etc. You should count gerrit changes that reference QTBUG instances. Those are the real “bug fixed”

@Massimo: The numbers I mentioned in the blog post are based on bugreports.qt.io bugs closed with resolution ‘fixed’ or ‘done’. In addition there always are improvements and fixes that are not done based on a bug report. Overall number of commits to Qt 5.9.7 is around 12.000 more than those in Qt 5.6.3 and Qt 5.12.0 has around 29.000 commits more than Qt 5.6.3. These include new features, bug fixes, performance improvements, security updates etc.

stlcours says:

Excellent work! The number of bug, 2000 or 5000, is so huge, why people could use Qt5.6.3 to develop so many softwares?
And the bugs left is still huge, about 10000 bugs? Could you make a version to eliminate most of them, otherwise there is so strange that we are developing with a library having so many bugs! What do you think about this fact?

@stlcours: Even though there are known bugs in a released version of Qt it is not necessarily as bad as it might first sound, because:
– Qt bug reports are fully transparent, i.e. all the bugs are publicly visible
– Qt is very widely used, which helps in finding bugs (a seldom used software with zero bugs is not necessarily of better quality than highly used software with known bugs)
– Any one application is unlikely to use all the functionality, so an application is not affected by all of the open bugs
– Qt is a cross-platform toolkit, so the bugs of a platform not used by the app are in a way irrelevant (for that app)
– Bugfixing is prioritized, so the most important bugs are fixed first (based on general importance and the customer reporting the issue, when known)
– Many bugs only happen when functionality is used in a particular way, thus not happening in all applications using the functionality
– Many bugs can be worked around and known workarounds are provided within the bug report or by support team
– Some of the bugs are so old that it might be actually better to not fix them as a change in behavior might cause worse effects
– Long-term supported Qt releases receive multiple patch releases providing bug fixes, but not bringing in new features
That said, of course the more bugs we can fix, the better. But having zero bugs before making a release is not the goal we are aiming to.

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