[llvm-dev] Using C++14 code in LLVM

[Reid Kleckner via llvm-dev]

On Tue, Oct 31, 2017 at 2:08 PM, Rui Ueyama via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

>
>> Issue: Ubuntu 14.04 LTS is on GCC 4.8.x, and we have to support it until
>> end of life.
>> Resolution: LTS is right around the corner, in 6 more months.
>>
>
> The existence of the newer version of LTS doesn't matter for those who are
> using older, but supported LTS, because it is supported. We cannot say to
> them that it is end of life so they should upgrade.
>

I don't think there's any reason we can't suggest they upgrade, especially
if they are two LTS releases behind. This would give LLVM a four-year
horizon on supporting compilers in any Ubuntu LTS release. Ubuntu's support
extends for five years, but there's no reason we should bend over backwards
to eke out that extra year of LLVM build support.


> That said, newer compilers are just one command away on Ubuntu 14.04 LTS.
> If I'm interpreting this page correctly https://packages.ubuntu.com/
> trusty/devel/, you can install any version of Clang between 3.3 to 3.9
> using apt-get, and I don't think doing that is too much hassle.
>

C++14 doesn't enhance just the language, it also adds library
functionality. I don't want to field user questions along the lines of "I'm
building on 14.04 with a custom installed version of clang and system
libstdc++ and I have this obscure build issue with std::map::emplace_back".
I also don't want to enforce a project policy of using only C++11 library
features by setting up a buildbot with a new compiler and old libstdc++.

As Zach said, I think if we just wait until April, we'll have a new Ubuntu
LTS, and we can target GCC 5.3.
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