Fix cross-compiling for Apple platforms #1389
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madsmtm
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madsmtm
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Feb 5, 2025
| # Test with clang/llvm for now, has better cross-compilation support (GCC requires downloading a different toolchain) | ||
| echo "CC=clang" >> $GITHUB_ENV | ||
| echo "CXX=clang++" >> $GITHUB_ENV | ||
| echo "AR=llvm-ar" >> $GITHUB_ENV |
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It is unclear to me why llvm-ar is required here, it seems to not be on my local Ubuntu 24 VM? But if we don't include it, we fail with:
rust-lld: error: /home/runner/work/cc-rs/cc-rs/target/aarch64-apple-darwin/debug/build/cc-test-5875314a6fda6e38/out/libOptLinkage.a: archive has no index; run ranlib to add one
rust-lld: error: undefined symbol: _answer
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No idea maybe there's some apple/clang stuff default ar not supporting?
NobodyXu
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Feb 5, 2025
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I'm not sure if this is relevant to the last fix, but trying to bump cc in rust gives us rust-lang/rust#136720 (comment) |
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Hmm, that's what #1384 fixed. Seems like it's not failing in bootstrap, but when building |
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(So, of course we weren't done here...)
Basically, the only difference between this and pre-#1384 is that on visionOS and Mac Catalyst, we pass a versioned
--targetinstead of unversioned--target+-mtargetos=.This is similar to the alternative I noted in that PR, and while it does run into #1278 (the bug that configuration files + versioned targets are badly supported on older Clang) on those targets, I think that's the better option.
Fixes #1388. To avoid this in the future, I have added a CI step to verify that cross-compilation works (fails in the first commit, succeeds in the second).
Alternatives
I looked through Clang's parsing code, and from that I glean that an alternative would probably be to set
--target+*_DEPLOYMENT_TARGET. This has a few problems though:Tool::args/.get_compiler().get_command().get_args(), and forget to also look atTool::env(I know at least Rust'sbootstrapcurrently forgets to do this).-mmacosx-version-min=there) (probably acceptable to not do if we did Detect common misconfigurations on error #1391).