[clang] [Clang] Add __datasizeof (PR #67805)

[via cfe-commits]

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@@ -236,6 +236,7 @@ FEATURE(shadow_call_stack,
 FEATURE(tls, PP.getTargetInfo().isTLSSupported())
 FEATURE(underlying_type, LangOpts.CPlusPlus)
 FEATURE(experimental_library, LangOpts.ExperimentalLibrary)
+FEATURE(datasizeof, LangOpts.CPlusPlus)
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philnik777 wrote:

The problem with `EXTENSION` is that it's influenced by `-pedantic-errors`, which makes it pretty much useless for standard libraries.

https://github.com/llvm/llvm-project/pull/67805