[libcxx-commits] [PATCH] D62428: [libcxx] Slightly improved policy for handling experimental features

[Louis Dionne via Phabricator via libcxx-commits]

ldionne added a comment.

In D62428#1518488 <https://reviews.llvm.org/D62428#1518488>, @mclow.lists wrote:

> The deletions are fine, the doc updates are good, but I think deprecation warnings are not.
>  Things that are going to happen in the future (a year from now, say) or never (if people don't update their tools) don't belong in the warning spew for **every single build**


Okay, so we've had offline discussions about this, and the general idea I got is that you would prefer that these warnings be in a tool like `clang-tidy`, that users can run only when they so desire. Please correct me if that's incorrect.

However, the key thing here is that I would like for these warnings to be opt-OUT, not opt-IN. This is really important for me, as otherwise most users are not even aware of the situation and they don't turn the warnings on (aka run the tool). Hence, using `clang-tidy` or any similar solution that is NOT in the mandatory compilation workflow is not sufficient.

Furthermore, I think this is, at the end of the day, a vendor decision. I don't think having these warnings (or not having them) makes much of a difference for libc++ as an open source project, however it makes a big difference for vendors. I feel like this issue is important enough that we would do this downstream if we were only given that choice. However, one thing I would suggest in order to resolve the stalemate is to guard these deprecation warnings behind a CMake configuration option (for example). That way, vendors can decide whether they want their libc++ to contain the warnings or not, and upstream libc++ can decide to do differently. The downside with this solution is that we add yet another configuration that must be tested, but it's better than nothing.

@mclow.lists  How do you feel about that compromise?


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