How do I cross compile a Rust application from macOS x86 to macOS Silicon?

Question

I want to cross compile a Rust program from my x86 Mac to a binary that can run on a Silicon Mac, and I can't figure out linking.

I have:

• An x86 Mac running macOS 10.15.7 Catalina
• A Rust project called riff
• cargo 1.51.0 (43b129a20 2021-03-16) recently retrieved using rustup
• Xcode version 12.4 (12D4e)

I want to compile this into a binary that can run on a Silicon (ARM) Mac. This could be one of:

• A Silicon specific binary
• A Universal binary that can run on either Silicon or x86

I have tried (through ./release.sh --dry):

• rustup target add aarch64-apple-darwin
• cargo build --release --target=aarch64-apple-darwin

The result was too long to paste in here, so this is an excerpt:

   Compiling riff v0.1.0 (/Users/johan/src/riff)
error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-arch arm64" "-L" "/Users/johan/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-darwin/lib" "/Users/johan/src/riff/target/aarch64-apple-darwin/release/deps/riff.1g47gi93dk96t2va.rcgu.o" ... "/Users/johan/src/riff/target/aarch64-apple-darwin/release/deps/riff.thread_local-9baf7723f72eef37.thread_local.7fl1y1d9-cgu.9.rcgu.o.rcgu.o" "/Users/johan/src/riff/target/aarch64-apple-darwin/release/deps/riff.unwind-082f7f4ff792426f.unwind.7rkx2ya0-cgu.0.rcgu.o.rcgu.o" "-o /Users/johan/src/riff/target/aarch64-apple-darwin/release/deps/riff" "-Wl,-dead_strip" "-nodefaultlibs" "-L" "/Users/johan/src/riff/target/aarch64-apple-darwin/release/deps" "-L" "/Users/johan/src/riff/target/release/deps" "-L" "/Users/johan/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-darwin/lib" "/Users/johan/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-darwin/lib/libcompiler_builtins-9eb7dc999785b765.rlib" "-lSystem" "-lresolv" "-lc" "-lm"
  = note: ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libresolv.tbd, missing required architecture arm64 in file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libresolv.tbd
          ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libm.tbd, missing required architecture arm64 in file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libm.tbd
          ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libc.tbd, missing required architecture arm64 in file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libc.tbd
          ld: warning: ignoring file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libSystem.tbd, missing required architecture arm64 in file /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib/libSystem.tbd
          Undefined symbols for architecture arm64:
            "__tlv_atexit", referenced from:
                std::sys::unix::thread_local_dtor::register_dtor::h4ece0fa32a190720 in riff.std-e40bd6a3af835df4.std.5bd9rdky-cgu.0.rcgu.o.rcgu.o
...
            "_free", referenced from:
                alloc::raw_vec::finish_grow::hd210c40bc8674cab (.llvm.18296587876935678160) in riff.addr2line-220464f1af330a49.addr2line.6xizm3st-cgu.1.rcgu.o.rcgu.o
                addr2line::path_push::hf1048f2514c3ed28 in riff.addr2line-220464f1af330a49.addr2line.6xizm3st-cgu.5.rcgu.o.rcgu.o
                alloc::raw_vec::finish_grow::ha5f485527a5c6598 in riff.addr2line-a950b2eed913eb15.addr2line.1hygsg7c-cgu.0.rcgu.o.rcgu.o
                addr2line::path_push::h891160d400ff153e in riff.addr2line-a950b2eed913eb15.addr2line.1hygsg7c-cgu.0.rcgu.o.rcgu.o
                core::ptr::drop_in_place$LT$aho_corasick..prefilter..Packed$GT$::h03bcd2abfab8068d in riff.aho_corasick-5d6c900557669556.aho_corasick.4z4l4vb2-cgu.0.rcgu.o.rcgu.o
                core::ptr::drop_in_place$LT$aho_corasick..packed..pattern..Patterns$GT$::h0c7fda104debb352 in riff.aho_corasick-5d6c900557669556.aho_corasick.4z4l4vb2-cgu.0.rcgu.o.rcgu.o
                core::ptr::drop_in_place$LT$alloc..vec..Vec$LT$alloc..vec..Vec$LT$u8$GT$$GT$$GT$::h75f2b558c0581f8d in riff.aho_corasick-5d6c900557669556.aho_corasick.4z4l4vb2-cgu.0.rcgu.o.rcgu.o
                ...
               (maybe you meant: alloc::alloc::box_free::ha8718384ecb60252 (.llvm.10945926475227631812), alloc::alloc::box_free::h58e664059c03effd (.llvm.10945926475227631812) , alloc::alloc::box_free::h75cae1a8684a32ce (.llvm.8938487907768303252) , alloc::alloc::box_free::h0459f8e1bcc5ae0a (.llvm.8938487907768303252) , alloc::alloc::box_free::hc3b2f94f9be4da06 (.llvm.7882408235892284297) , alloc::alloc::box_free::h75cae1a8684a32ce (.llvm.7882408235892284297) , alloc::alloc::box_free::h0459f8e1bcc5ae0a (.llvm.11547294393004044273) , alloc::alloc::box_free::hcc8806ce168336a8 (.llvm.2537316772799228199) , alloc::alloc::box_free::h305ed20a6d3d49c7 (.llvm.11075277010792284734) , alloc::alloc::box_free::h384e6b725c5ad166 (.llvm.7882408235892284297) , alloc::alloc::box_free::h0459f8e1bcc5ae0a (.llvm.7882408235892284297) , alloc::alloc::box_free::hb8cf920d803cfa22 (.llvm.4992613404806278909) , alloc::alloc::box_free::h90dd1ed16b644fc1 (.llvm.9562203231941335137) , alloc::alloc::box_free::h9e3286b91a0737ba (.llvm.4992613404806278909) , alloc::alloc::box_free::h75cae1a8684a32ce (.llvm.11547294393004044273) )
          ld: symbol(s) not found for architecture arm64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

Add the appropriate target

rustup target add aarch64-apple-darwin

Compile your code using the macOS 11.x SDK ¹:

SDKROOT=$(xcrun -sdk macosx11.1 --show-sdk-path) \
MACOSX_DEPLOYMENT_TARGET=$(xcrun -sdk macosx11.1 --show-sdk-platform-version) \
cargo build --target=aarch64-apple-darwin

This produces a single-architecture binary:

file target/aarch64-apple-darwin/debug/riff
target/aarch64-apple-darwin/debug/riff: Mach-O 64-bit executable arm64

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1 — Find what the current available SDKs are via xcodebuild -showsdks.