[libcxx-commits] [libcxx] [libcxx] changes `__is_allocator` from a struct to a variable or concept (PR #68629)

[Louis Dionne via libcxx-commits]

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@@ -57,6 +57,8 @@
     # Disable warnings for extensions used in C++03
     "-Wno-local-type-template-args",
     "-Wno-c++11-extensions",
+    "-Wno-c++14-extensions",
+    "-Wno-c++17-extensions",
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ldionne wrote:

Also we would need to ensure that if users are using `-isystem` to include libc++, they never get these extension warnings. If they started to for some reason, for example an extension is used in a default argument and that triggers a diagnostic from the user's code despite `-isystem`, then we should catch that. IDK if that's even possible, but I think it would be safer to find a way not to disable extension warnings for the whole test suite.

It doesn't have to be done as part of this review, but I think it's important enough that we'd want to do it as a follow-up: shipping a bug of that sort could be quite disruptive and it would be even more embarrassing since it seems really easy to catch from a user's perspective.

https://github.com/llvm/llvm-project/pull/68629