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

Zachary Turner via llvm-dev llvm-dev at lists.llvm.org
Wed Nov 1 09:24:03 PDT 2017

On Tue, Oct 31, 2017 at 11:23 PM Zachary Turner <zturner at google.com> wrote:

> I’m ok with that, but the reason I’m pushing is because there is no clear
> plan of action. Even if the plan of action is “When X happens, we can
> enable C++14”, that’s fine too. I just want to know, concretely, what is X.
> We should either be able to say never or give a reasonable set of
> conditions that would enable a switch. All I’ve seen though is “it’s hard”
> which just means I’m going to ask again next year, and the year after, etc
> due to lack of clear guidance.
> To address your point though , this isn’t really about building everything
> with clang. You don’t need to bootstrap Clang to build a hypothetical C++17
> enabled LLVM, you could also bootstrap a more modern version of GCC.
> This is really more fundamentally about “Can we have a clearly defined
> policy about how often we can bump the minimum compiler version, like we
> have for MSVC?”

To make this even more concrete, let me offer a proposal:

* We can bump the minimum required non-Microsoft toolchain version every 4

Having something written like this allows us to have a schedule, and having
a schedule allows downstream consumers to plan upgrades as needed so as to
minimize disruption.

4 years is also a pretty reasonable amount of time IMO, but we can
certainly discuss the exact value of N.

I haven't said anything here about what it can be bumped *to*.  But in the
interest of making progress, I'm separating the decisions out into smaller
pieces so we can focus on one thing at a time.
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