Cannot cross-compile rust crate for macOS

[hardcore-sushi]

Everything goes fine when I try to build the crate for GNU/Linux, Windows or even Android but when I set x86_64-apple-darwin as the target, I get the following error:

   ....
   Compiling blake3 v0.3.8
The following warnings were emitted during compilation:

warning: The C compiler "cc" does not support -mavx512f and -mavx512vl.
warning: cc: error: x86_64: No such file or directory
warning: cc: error: unrecognized command-line option ‘-arch’

error: failed to run custom build command for `blake3 v0.3.8`

Caused by:
  process didn't exit successfully: `/tmp/blake3-test/target/release/build/blake3-4842eee2252bfd15/build-script-build` (exit status: 1)
  --- stdout
  cargo:rerun-if-env-changed=CARGO_FEATURE_PURE
  TARGET = Some("x86_64-apple-darwin")
  HOST = Some("x86_64-unknown-linux-gnu")
  CC_x86_64-apple-darwin = None
  CC_x86_64_apple_darwin = None
  TARGET_CC = None
  CC = None
  CROSS_COMPILE = None
  CFLAGS_x86_64-apple-darwin = None
  CFLAGS_x86_64_apple_darwin = None
  TARGET_CFLAGS = None
  CFLAGS = None
  CRATE_CC_NO_DEFAULTS = None
  CARGO_CFG_TARGET_FEATURE = Some("fxsr,sse,sse2,sse3,ssse3")
  OPT_LEVEL = Some("3")
  CC_x86_64-apple-darwin = None
  CC_x86_64_apple_darwin = None
  TARGET_CC = None
  CC = None
  CROSS_COMPILE = None
  CFLAGS_x86_64-apple-darwin = None
  CFLAGS_x86_64_apple_darwin = None
  TARGET_CFLAGS = None
  CFLAGS = None
  CRATE_CC_NO_DEFAULTS = None
  DEBUG = Some("false")
  CARGO_CFG_TARGET_FEATURE = Some("fxsr,sse,sse2,sse3,ssse3")
  cargo:warning=The C compiler "cc" does not support -mavx512f and -mavx512vl.
  cargo:rerun-if-env-changed=BLAKE3_CI
  cargo:rerun-if-env-changed=CARGO_FEATURE_PREFER_INTRINSICS
  cargo:rerun-if-env-changed=CARGO_FEATURE_PURE
  cargo:rustc-cfg=blake3_sse2_ffi
  cargo:rustc-cfg=blake3_sse41_ffi
  cargo:rustc-cfg=blake3_avx2_ffi
  TARGET = Some("x86_64-apple-darwin")
  OPT_LEVEL = Some("3")
  HOST = Some("x86_64-unknown-linux-gnu")
  CC_x86_64-apple-darwin = None
  CC_x86_64_apple_darwin = None
  TARGET_CC = None
  CC = None
  CROSS_COMPILE = None
  CFLAGS_x86_64-apple-darwin = None
  CFLAGS_x86_64_apple_darwin = None
  TARGET_CFLAGS = None
  CFLAGS = None
  CRATE_CC_NO_DEFAULTS = None
  DEBUG = Some("false")
  CARGO_CFG_TARGET_FEATURE = Some("fxsr,sse,sse2,sse3,ssse3")
  running: "cc" "-O3" "-ffunction-sections" "-fdata-sections" "-fPIC" "-m64" "-arch" "x86_64" "-Wall" "-Wextra" "-std=c11" "-o" "/tmp/blake3-test/target/x86_64-apple-darwin/release/build/blake3-d3c1ad758db1c04d/out/c/blake3_sse2_x86-64_unix.o" "-c" "c/blake3_sse2_x86-64_unix.S"
  cargo:warning=cc: error: x86_64: No such file or directory
  cargo:warning=cc: error: unrecognized command-line option ‘-arch’
  exit status: 1

  --- stderr


  error occurred: Command "cc" "-O3" "-ffunction-sections" "-fdata-sections" "-fPIC" "-m64" "-arch" "x86_64" "-Wall" "-Wextra" "-std=c11" "-o" "/tmp/blake3-test/target/x86_64-apple-darwin/release/build/blake3-d3c1ad758db1c04d/out/c/blake3_sse2_x86-64_unix.o" "-c" "c/blake3_sse2_x86-64_unix.S" with args "cc" did not execute successfully (status code exit status: 1).


warning: build failed, waiting for other jobs to finish...
error: build failed

OS: Linux 5.10.0-8-amd64 #1 SMP Debian 5.10.46-1 (2021-06-24) x86_64 GNU/Linux
Rust version: v1.53.0
"cc -v" output:

Using built-in specs.
COLLECT_GCC=cc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/10/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa:hsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 10.2.1-6' --with-bugurl=file:///usr/share/doc/gcc-10/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-10 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none=/build/gcc-10-Km9U7s/gcc-10-10.2.1/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-10-Km9U7s/gcc-10-10.2.1/debian/tmp-gcn/usr,hsa --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu --with-build-config=bootstrap-lto-lean --enable-link-mutex
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.2.1 20210110 (Debian 10.2.1-6)

[oconnor663]

unrecognized command-line option ‘-arch’ seems to be the core issue. I wonder if this is the cc crate getting confused in a cross-compiling scenario. Do you have any generic steps to repro this issue, for example maybe building the b3sum crate?

[hardcore-sushi]

I get the same error when cross-compiling b3sum, and it seems to use blake3 v0.3.7.

[cipriancraciun]

So I've hit the same problem compiling my tool that depends on blake3.

The problem (at least for me) seems to be that the crate uses the wrong C compiler, namely cc, which most likely it's a symlink to one of the native compilers either GCC or Clang. You'll have to convince it to use the proper cross-compiler.

Assuming that you are using osxcross, here is how I've managed to make it build:

• start with a clean environment (in my case I've actually called env -i PATH=... TMPDIR=... ... cargo ...;
• export PATH="/opt/osxcross/bin:/usr/bin:/bin" -- make sure it doesn't pick the wrong compiler from somewhere else;
• export CC=x86_64-apple-darwin21.4-clang -- use the osxcross compiler for C;
• export CXX=x86_64-apple-darwin21.4-clang++ -- the same for C++;
• export AR=x86_64-apple-darwin21.4-ar -- also needed;
• export CARGO_TARGET_X86_64_APPLE_DARWIN_LINKER=x86_64-apple-darwin21.4-clang -- or just edit cargo.toml, but this environment variable should be enough;

After doing all this it now builds. (It works for both Linux-GNU, Linux-Musl, Android, Darwin, both x86_64 and aarch64.)

[jedisct1]

You need to use cargo-zigbuild to cross-compile Rust code that includes C code:

cargo zigbuild --target=x86_64-apple-darwin

[oconnor663]

@jedisct1 wow that is wonderful.

The complete pair of commands I just used to do a cross-compile was:

rustup target add x86_64-apple-darwin
cargo zigbuild --target=x86_64-apple-darwin

[jedisct1]

When targeting Linux, the command (actually Zig) also allows choosing a glibc version that may differ from the one installed on the system.

This is very useful to build redistributable binaries that work everywhere, even on CentOS 5.