C++17 is here

[Nico Weber]

(bcc blink-dev, chromium-dev for visibility; replies will go to the cxx@ list)

Hi,

All our toolchains now support C++17, and we've been building with -std=c++17 (or /std:c++17) on all bots for at least 1.5 weeks now. We can start using it!

We'll allow new language and library features gradually, like we did with C++11 and C++14. The motivation for this is to make sure each feature actually works on our toolchains, and to spread out adoption of things over time so that people have time to learn about the new features as we add them.

pkasting updated styleguide/c++/c++11.md in your checkout with C++17 features and libraries (thanks!). You can also view this file online: https://chromium.googlesource.com/chromium/src/+/main/styleguide/c++/c++11.md

That file documents the process for adopting new features at the top. In short: For any feature in the "C++17 TBD Language Features" or "C++17 TBD Library Features" lists in that document that you think we should adopt, send a short proposal to c...@chromium.org. If folks like it, send a CL that moves the feature to the corresponding "Allowed" list in that doc. Ideally, include a use of that feature in the same CL, so that the CQ can verify that it works on all platforms.

You can also propose a feature to be banned in Chromium. Generally, we only try to ban what's banned in the regular Google style guide, so you should have a good reason for why the decision should be different for Chromium.

Every once in a while, we'll send a summary of newly-allowed and newly-banned things to chromium-dev.

Again, part of the motivation here is to spread the new things out over time a bit, so please don't send a thread for every single feature immediately :)

Cheers,

Nico