Error when cross-compiling to macOS with cc 1.2.12

[tuxu]

I have cross-compilation from Linux to macOS set up for a project. cc 1.2.12 omits the --target argument, which Clang (currently using 18.1.8) doesn't like.

Minimum reproducible example with a dummy project:

$ export CARGO_TARGET_AARCH64_APPLE_DARWIN_RUSTFLAGS="-C linker=clang -C link-arg=--target=aarch64-apple-darwin -C link-arg=-fuse-ld=lld"
$ cargo new hello
$ cd hello
$ cargo add bzip2
$ cargo build --target aarch64-apple-darwin

This fails with:

  cargo:warning=clang: error: unsupported option '-arch' for target 'aarch64-unknown-linux-gnu'
  cargo:warning=clang: warning: argument unused during compilation: '-mmacosx-version-min=11.0' [-Wunused-command-line-argument]

  --- stderr


  error occurred in cc-rs: Command LC_ALL="C" "clang" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-2" "-fno-omit-frame-pointer" "-arch" "arm64" "-mmacosx-version-min=11.0" "-I" "bzip2-1.0.8" "-D_FILE_OFFSET_BITS=64" "-DBZ_NO_STDIO" "-o" "/tmp/hello/target/aarch64-apple-darwin/debug/build/bzip2-sys-9c6e283515f24e27/out/lib/a9dc8ba631b1466a-blocksort.o" "-c" "bzip2-1.0.8/blocksort.c" with args clang did not execute successfully (status code exit status: 1).

Click for full output

root@ac6839d585fb:/tmp# curl -L "https://github.com/phracker/MacOSX-SDKs/releases/download/11.0-11.1/MacOSX11.0.sdk.tar.xz" | tar xJ -C /opt
root@ac6839d585fb:/tmp# export SDKROOT=/opt/MacOSX11.0.sdk
root@ac6839d585fb:/tmp# export CARGO_TARGET_AARCH64_APPLE_DARWIN_RUSTFLAGS="-C linker=clang -C link-arg=--target=aarch64-apple-darwin -C link-arg=-fuse-ld=lld"
root@ac6839d585fb:/tmp# rustc --version
rustc 1.84.1 (e71f9a9a9 2025-01-27)
root@ac6839d585fb:/tmp# clang --version
clang version 18.1.8 (http://git.linaro.org/toolchain/jenkins-scripts.git e5def089cd9f5aa71524f82fef301ca66eaa38d2)
Target: aarch64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/llvm/18.1.8/bin
root@ac6839d585fb:/tmp# cargo new hello
    Creating binary (application) `hello` package
note: see more `Cargo.toml` keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
root@ac6839d585fb:/tmp# cd hello
root@ac6839d585fb:/tmp/hello# cargo add bzip2
    Updating crates.io index
      Adding bzip2 v0.5.0 to dependencies
             Features:
             - libbz2-rs-sys
             - static
    Updating crates.io index
     Locking 6 packages to latest compatible versions
root@ac6839d585fb:/tmp/hello# cargo build --target aarch64-apple-darwin
   Compiling shlex v1.3.0
   Compiling pkg-config v0.3.31
   Compiling libc v0.2.169
   Compiling cc v1.2.12
   Compiling bzip2-sys v0.1.11+1.0.8
warning: bzip2-sys@0.1.11+1.0.8: clang: error: unsupported option '-arch' for target 'aarch64-unknown-linux-gnu'
warning: bzip2-sys@0.1.11+1.0.8: clang: warning: argument unused during compilation: '-mmacosx-version-min=11.0' [-Wunused-command-line-argument]
error: failed to run custom build command for `bzip2-sys v0.1.11+1.0.8`

Caused by:
  process didn't exit successfully: `/tmp/hello/target/debug/build/bzip2-sys-a1f70d461238d3ac/build-script-build` (exit status: 1)
  --- stdout
  cargo:rerun-if-env-changed=BZIP2_NO_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_aarch64-apple-darwin
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_aarch64_apple_darwin
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_ALLOW_CROSS
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64-apple-darwin
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64_apple_darwin
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_aarch64-apple-darwin
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_aarch64_apple_darwin
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR
  OPT_LEVEL = Some(0)
  TARGET = Some(aarch64-apple-darwin)
  HOST = Some(aarch64-unknown-linux-gnu)
  cargo:rerun-if-env-changed=CC_aarch64-apple-darwin
  CC_aarch64-apple-darwin = None
  cargo:rerun-if-env-changed=CC_aarch64_apple_darwin
  CC_aarch64_apple_darwin = None
  cargo:rerun-if-env-changed=TARGET_CC
  TARGET_CC = None
  cargo:rerun-if-env-changed=CC
  CC = Some(clang)
  cargo:rerun-if-env-changed=CC_KNOWN_WRAPPER_CUSTOM
  CC_KNOWN_WRAPPER_CUSTOM = None
  RUSTC_WRAPPER = None
  cargo:rerun-if-env-changed=CC_ENABLE_DEBUG_OUTPUT
  cargo:rerun-if-env-changed=CRATE_CC_NO_DEFAULTS
  CRATE_CC_NO_DEFAULTS = None
  DEBUG = Some(true)
  cargo:rerun-if-env-changed=MACOSX_DEPLOYMENT_TARGET
  MACOSX_DEPLOYMENT_TARGET = None
  cargo:rerun-if-env-changed=CFLAGS_aarch64-apple-darwin
  CFLAGS_aarch64-apple-darwin = None
  cargo:rerun-if-env-changed=CFLAGS_aarch64_apple_darwin
  CFLAGS_aarch64_apple_darwin = None
  cargo:rerun-if-env-changed=TARGET_CFLAGS
  TARGET_CFLAGS = None
  cargo:rerun-if-env-changed=CFLAGS
  CFLAGS = None
  CARGO_ENCODED_RUSTFLAGS = Some(-Clinker=clang-Clink-arg=--target=aarch64-apple-darwin-Clink-arg=-fuse-ld=lld)
  cargo:warning=clang: error: unsupported option '-arch' for target 'aarch64-unknown-linux-gnu'
  cargo:warning=clang: warning: argument unused during compilation: '-mmacosx-version-min=11.0' [-Wunused-command-line-argument]

  --- stderr


  error occurred in cc-rs: Command LC_ALL="C" "clang" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-gdwarf-2" "-fno-omit-frame-pointer" "-arch" "arm64" "-mmacosx-version-min=11.0" "-I" "bzip2-1.0.8" "-D_FILE_OFFSET_BITS=64" "-DBZ_NO_STDIO" "-o" "/tmp/hello/target/aarch64-apple-darwin/debug/build/bzip2-sys-9c6e283515f24e27/out/lib/a9dc8ba631b1466a-blocksort.o" "-c" "bzip2-1.0.8/blocksort.c" with args clang did not execute successfully (status code exit status: 1).

It works when downgrading cc to 1.2.11:

root@ac6839d585fb:/tmp/hello# cargo update -p cc --precise 1.2.11
    Updating crates.io index
 Downgrading cc v1.2.12 -> v1.2.11
root@ac6839d585fb:/tmp/hello# cargo build --target aarch64-apple-darwin
  Downloaded cc v1.2.11
  Downloaded 1 crate (102.0 KB) in 0.13s
   Compiling cc v1.2.11
   Compiling bzip2-sys v0.1.11+1.0.8
   Compiling bzip2 v0.5.0
   Compiling hello v0.1.0 (/tmp/hello)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.80s

I can work around by adding --target=aarch64-apple-darwin to CFLAGS_aarch64_apple_darwin.

[madsmtm]

Argh!

[madsmtm]

I'll have a look, thanks for the report.

[madsmtm]

I have cross-compilation from Linux to macOS set up for a project

Could you share your project setup (if it's GitHub Actions or similar)? I'd like to configure something similar for this repo when fixing the bug.

[tuxu]

It's an internal project, but I'm happy to share a trimmed down Dockerfile:

Click here

FROM ubuntu:22.04

ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get -qq update \
    && apt-get -qq install -y curl \
       make cmake ninja-build pkg-config \
       libc6-dev libgcc-11-dev libstdc++-11-dev \
    && rm -rf /var/lib/apt/lists/*

ENV LLVM_VERSION=18.1.8
RUN mkdir -p /opt/llvm/$LLVM_VERSION \
    && url=https://github.com/llvm/llvm-project/releases/download/llvmorg-${LLVM_VERSION}/$(test $(arch) = aarch64 && echo "clang+llvm-${LLVM_VERSION}-aarch64-linux-gnu.tar.xz" || echo "clang+llvm-${LLVM_VERSION}-x86_64-linux-gnu-ubuntu-18.04.tar.xz") \
    && curl --fail -L $url | tar xJ --strip-components=1 -C /opt/llvm/$LLVM_VERSION
ENV PATH=/opt/llvm/$LLVM_VERSION/bin:$PATH

ARG RUST_VERSION=1.84.1
RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
    | bash -s -- -y --default-toolchain=$RUST_VERSION
ENV PATH="/root/.cargo/bin:$PATH"

# Cross-compilation targets
RUN rustup target add \
    x86_64-apple-darwin \
    aarch64-apple-darwin

# Install macOS SDKs
RUN curl -L "https://github.com/phracker/MacOSX-SDKs/releases/download/11.0-11.1/MacOSX11.0.sdk.tar.xz" | tar xJ -C /opt
ENV SDKROOT=/opt/MacOSX11.0.sdk

# Set default compiler
ENV CC=clang CXX=clang++

# Set flags for cross-compilation
ENV CARGO_TARGET_X86_64_APPLE_DARWIN_RUSTFLAGS="-C linker=clang -C link-arg=--target=x86_64-apple-darwin -C link-arg=-fuse-ld=lld"
ENV CARGO_TARGET_AARCH64_APPLE_DARWIN_RUSTFLAGS="-C linker=clang -C link-arg=--target=aarch64-apple-darwin -C link-arg=-fuse-ld=lld"

# Workaround for cc-rs 1.2.12, see: https://github.com/rust-lang/cc-rs/issues/1388
ENV CFLAGS_x86_64_apple_darwin="--target=x86_64-apple-darwin"
ENV CFLAGS_aarch64_apple_darwin="--target=aarch64-apple-darwin"

# Trial build for supported platforms
RUN cd /tmp \
    && cargo new foo \
    && cd foo \
    # add dependency on C library for testing
    && cargo add bzip2 \
    # macOS builds through Clang + LLD
    && cargo build --target aarch64-apple-darwin \
    && cargo build --target x86_64-apple-darwin \
    && rm -rf /tmp/foo

[madsmtm]

Thanks! I've filed #1389, and added a CI step loosely based on your work.

[tuxu]

That's fantastic. Thanks for the swift fix!