[PATCH] D136315: [clang][Darwin] Try to guess the SDK root with xcrun when unspecified

Thu Jan 19 07:31:40 PST 2023

calebzulawski added a comment.

In D136315#4065481 <https://reviews.llvm.org/D136315#4065481>, @thakis wrote:

> In D136315#4065426 <https://reviews.llvm.org/D136315#4065426>, @calebzulawski wrote:
>
>> I don't think we necessarily need to revert due to the xcrun quirk since I think it's harmless, though I can provide a follow up change if necessary.  I just checked Rust's source as a comparison and it appears that for macOS targets it will always attempt to invoke xcrun regardless of host as well.
>
> Needlessly spawning additional processes doesn't seem "harmless" to me.
>
> If you can fix quickly, sure, do that.
>
>> I could see a macOS cross-compiler environment providing an xcrun replacement, for example.
>
> That's theoretically possible I suppose, but it doesn't exist. No mac cross compiling uses `xcrun`.

Sorry, I agree that we shouldn't do things needlessly, but xcrun is only invoked if the compiler otherwise can't figure out the sysroot.  I just tried using `--target=x86_64-apple-macos` on its own on Linux and sure enough the sysroot included `/usr/include` etc, which is surely also wrong.  I suspect any existing cross-compiler environments either set SDKROOT or pass a sysroot flag, otherwise they wouldn't work (and this change doesn't affect them).

It seems osxcross does provide an xcrun replacement: https://github.com/tpoechtrager/osxcross/blob/master/wrapper/programs/xcrun.cpp

>> The test failures are another issue but I still don't quite understand the cause.
>
> I can investigate a bit more. Which version of macOS are you running? Are you using system python3 or brew python3? I know that system python3 sets SDKROOT by default on macOS 13+ for some reason, so maybe that's related. (The bot runs macOS 13.)

I'm using 13.1 and I do have brew python installed.  I see what you're describing, system python has SDKROOT set.

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