[PATCH] D157283: [clang] Match -isysroot behaviour with system compiler on Darwin

Tue Sep 19 09:34:30 PDT 2023

ldionne added a comment.

In D157283#4614177 <https://reviews.llvm.org/D157283#4614177>, @DmitryPolukhin wrote:

> @ldionne could you please upstream 9edb9a711503d540cf3126c0fde11ce9a0d9a7aa <https://reviews.llvm.org/rG9edb9a711503d540cf3126c0fde11ce9a0d9a7aa> (I don't know what it is)?
> Alternatively I can figure out what to do with this test (it is just copies of the same test with minimal modifications) with a hint how it was resolved to make sure that it worn diverse from want it should be on Darwin.

As explained in https://reviews.llvm.org/D89001#4648241, upstream Clang is the way it should be right now. The intent is that we first look along the `clang` binary for headers (that way if you install a custom libc++ it will be picked up), and then we fall back to the SDK version. It's just unfortunate that AppleClang has lagged behind a bit and created some confusion, but I believe the latest release should have the exact same behavior as upstream Clang wrt search paths. The commit mentioned above (`9edb9a711503d540cf3126c0fde11ce9a0d9a7aa`) as actually just making downstream back in sync with upstream. So IMO the correct thing to do is to abandon this change and wait for a new AppleClang that has matching behavior with upstream Clang (it's probably in Xcode 15 RC which came out recently).

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https://reviews.llvm.org/D157283