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

[Zachary Turner via llvm-dev]

I'm not familiar with the release process, but couldn't most of the
concerns raised in this thread be addressed by shipping prebuilt binaries
for these big platforms with older toolchains? How much of a burden is that
on the release maintainer?

I ask because many of these LTS distros are notoriously slow at updating
their packages. While some people may think C++14 doesn't provide enough
bang for the buck to justify bumping to GCC 4.9, C++17 definitely does. But
at that point we're going to be talking about GCC 6.1 or 6.2, which is
going to be significantly harder unless we want to wait 5-7 years, and I
suspect people won't.

So it might be worth it to start thinking about a long term solution early


On Tue, Oct 4, 2016 at 1:04 AM David Chisnall <David.Chisnall at cl.cam.ac.uk>
wrote:

> On 3 Oct 2016, at 20:06, Reid Kleckner via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >
> > I'm not in favor of dropping GCC 4.8 support yet. It's the default
> compiler for Ubuntu Trusty, which is from 2014, which isn't that old. I
> think it's important that LLVM build out of the box with the commonly
> installed system compiler.
>
> We are currently using Trusty (14.04) on our teaching machines - it’s an
> LTS release that’s still supported.  We upgraded two years ago because we
> couldn’t build LLVM with the previous LTO release without my needing to
> build gcc, libstdc++, and CMake from source and install them with futzed
> rpaths.  This was a very fragile environment for teaching.
>
> We’re likely to keep 14.04 for another year, because 16.04 breaks various
> things used in other courses.  Building the latest LLVM release wasn’t too
> bad this time, but it did require that I built a new CMake, because
> apparently some time between 3.7 and 3.9 we bumped the minimum CMake
> requirement to one that doesn’t ship with 14.04.
>
> If anyone is looking to hire students with LLVM experience, please
> remember that most university lab systems are using some form of long-term
> support release of their institution's favourite OS and it’s hard to
> persuade people to teach using LLVM if they can’t even build it on their
> lab machines.
>
> David
>
>
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