[webkit-dev] update GCC version?

[Michael Catanzaro]

On Sun, 2017-01-08 at 18:59 +0100, zan at falconsigh.net wrote:
> For the record, GCC 5 has complete C++14 support. The current
> requirement is 4.9, so the bump would be minimal.
> https://gcc.gnu.org/projects/cxx-status.html#cxx14

We would need to redefine our dependencies policy:

https://trac.webkit.org/wiki/WebKitGTK/DependenciesPolicy

We just recently crafted that policy. I kinda like it because it
provides a clear formula for deciding whether a compiler is too new to
be required or not. It means we would support GCC 4.9 until roughly
next spring/summer, one year from the next Debian release. We could
either (a) drop Debian from the policy, which I support doing anyway
because it does not take our security updates, or we could (b) define
the policy in terms of runtime dependencies, rather than build
dependencies (which I think Carlos Garcia wanted to do anyway). Either
way makes it more likely that distributions will get cut off and choose
to not provide WebKit security updates. I would prefer not to do (b),
because in practice distributions will just not take our updates if
they can't use their default compiler.

Keep in mind that for a distro to upgrade from GCC 4.9 -> 5.0 is weeks
of effort unless you build GCC with the flag that turns on the old C++
ABI, but you have to switch to the new ABI eventually, so might as well
do it at the same time. I have to support WebKit for a distribution
that has been delaying the upgrade for this reason. GCC upgrades are
expensive and not fun. Even turning off the ABI switch, upgrading GCC
means lots of obscure C++ build failures in packages you're not
familiar with.

Michael