[llvm-dev] Using C++14 code in LLVM (original) (raw)

UE US via llvm-dev llvm-dev at lists.llvm.org
Fri Nov 10 17:35:35 PST 2017

As long as the target is supported, I think the difficulty of rolling a cross chain is overrated, but I've done lots of them and I remember when it wasn't relatively easy. I don't see their being harder at first as a reason to impede progress with the language which, keep in mind, we're actually writing the compiler in... as long as nobody suggests a total port to Delphi. ;-)

GNOMETOYS

On Wed, Nov 1, 2017 at 11:24 AM, Zachary Turner via llvm-dev < llvm-dev at lists.llvm.org> wrote:

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 years. 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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