Some baseline thoughts

[Jan-Marek Glogowski]

Am 16.03.2017 um 12:20 schrieb Stephan Bergmann:
> Some of our baselines on current master (towards LO 5.4) are as follows:
> 
> 
> *  GCC 4.7
> (<https://cgit.freedesktop.org/libreoffice/core/commit/?id=e4b24c7399352642aeaeb412394d6230562d04d2>
> "configure: GCC 4.6 is no longer supported on master")
> 
> The latest version is GCC 6.  Noteworthy C++ conformance we would gain
> with a bump (according to
> <http://en.cppreference.com/w/cpp/compiler_support>) would be:
> 
> ** GCC 4.8.1:
> *** inheriting constructors
> *** ref-qualifiers

> ** GCC 4.9:
> *** decltype(auto), return type deduction for normal functions
> *** generic lambdas
> *** deprecated attribute
> *** single quote as digit separator
> 
> ** GCC 5:
> *** variable templates
> *** user-defined literals for <chrono> and <string>
> 
> The question is what old versions of GCC are required exactly by the
> various builds.

Ubuntu LTS 14.04 has 4.8 as the default compiler. An update for 4.9 is
the maximum available compiler.

> *  MSVC 2015 Update 3
> (<https://cgit.freedesktop.org/libreoffice/core/commit/?id=84b36c704d73362d4d86dc9e9c0efa0625958347>
> "Drop support for MSVC 2013")
> 
> Bumping this to MSVC 2017 is unlikely to happen anytime soon, given we
> bumped to MSVC 2015 Update 3 only recently.

Someone / the wiki claimed 2017 is already working, which is a
difference to the previous 2015 bump, which apparently took some time to
fix the fallout of the update.

> *  For --enable-compiler-plugins, Clang 3.4
> (<https://cgit.freedesktop.org/libreoffice/core/commit/?id=733198de1b7fc3907609217147704f493f6146e6>
> "Remove support for Clang < 3.4")
> 
> The latest version is Clang 4 (just released the other day).  Bumping
> this would allow to clean up some #ifdefs across compilerplugins/clang/.
>  The question is what old versions of Clang are required exactly by
> people building with --enable-compiler-plugins.
> 
> (For our C++ conformance, the oldest supported Clang version is rarely
> the limiting factor.)

Ubuntu doesn't have any official clang compiler, but provides a
clang-3.8 in the 14.04 repo, which I use for cross-checking.

I would just like to keep the 14.04 baseline because it makes backports
easier. We'll hopefully stay with 5.2 for a while, but I also thought so
about a 5.0 release, which was dropped.

JMG

P.S. 16.04 has gcc 5.3 as default and 5.4 as an update, clang still 3.8.