The UserManual states wrongly (AFAICT) that these default are not being defined for clang-cl, whereas further up the opposite is stated: https://github.com/llvm/llvm-project/blob/c86fe3ee0b92934f5d18394d9a0cdc1d3f0eef64/clang/docs/UsersManual.rst#L3375-L3382 I've chosen to follow that wording, as it's the latest related update. CC @RIscRIpt who recently touched this inb3e6ff3319CC @AaronBallman who cared about this, c.f.8fc0dcf036