cross confuses wrong target environment variables such as CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER when building for aarch64

[tgrushka]

Checklist

• I've looked through the issues and pull requests for similar reports

Describe your issue

Build fails with cross when I build with cross for Raspberry Pi, etc.:

cross build --target aarch64-unknown-linux-gnu

on my amd64 Linux system, and have local system environment for all my other, non-cross Rust projects:

export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER='/usr/bin/clang'
export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTFLAGS="-Z threads=8 -C linker=/usr/bin/clang -C link-arg=-fuse-ld=/usr/local/bin/mold"
export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTC_WRAPPER='/home/tom/.cargo/bin/sccache'

Error

cross build --target aarch64-unknown-linux-gnu
   Compiling proc-macro2 v1.0.92
   Compiling serde v1.0.216
   Compiling serde_json v1.0.134
error: linker `/usr/bin/clang` not found
  |
  = note: No such file or directory (os error 2)

error: could not compile `serde_json` (build script) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
...

When I remove those environment variables, my cross build succeeds:

set -e CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER
set -e CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTFLAGS
set -e CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTC_WRAPPER
cross build --target aarch64-unknown-linux-gnu
   Compiling proc-macro2 v1.0.92
   Compiling unicode-ident v1.0.14
   Compiling serde v1.0.216
   Compiling serde_json v1.0.134
...
   Compiling cross-test v0.1.0 (/project)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 1.83s

Conclusion: It seems cross is "confusing" the environment variables specific to one target with a different target.

Versions

cross --version
cross 0.2.5
[cross] note: Falling back to `cargo` on the host.
cargo 1.85.0-nightly (652623b77 2024-12-20)

rustc --version
rustc 1.85.0-nightly (bdc6b3de4 2024-12-23)

uname -a
Linux framework-mint 6.8.0-51-generic #52-Ubuntu SMP PREEMPT_DYNAMIC Thu Dec  5 13:09:44 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

What target(s) are you cross-compiling for?

aarch64-unknown-linux-gnu

Which operating system is the host (e.g computer cross is on) running?

• macOS
• Windows
• Linux / BSD
• other OS (specify in description)

What architecture is the host?

• x86_64 / AMD64
• arm32
• arm64 (including Mac M1)

What container engine is cross using?

• docker
• podman
• other container engine (specify in description)

cross version

cross 0.2.5

Example

This error seems not to occur in a new project with no dependencies, so let's add some:

cargo new cross-test
cd cross-test
cargo add serde serde-json

Ensure it works with default config (ensure a clean shell with no CARGO_TARGET_ variables set):

env | grep CARGO_TARGET_

cross build --target aarch64-unknown-linux-gnu

Build succeeds. Add different target config than building with cross:

export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER='/usr/bin/clang'
export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTFLAGS="-Z threads=8 -C linker=/usr/bin/clang -C link-arg=-fuse-ld=/usr/local/bin/mold"
export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTC_WRAPPER='/home/tom/.cargo/bin/sccache'

cross build --target aarch64-unknown-linux-gnu

Build fails:

cross build --target aarch64-unknown-linux-gnu
   Compiling serde v1.0.216
   Compiling serde_json v1.0.134
   Compiling ryu v1.0.18
   Compiling itoa v1.0.14
   Compiling memchr v2.7.4
error: linker `/usr/bin/clang` not found
  |
  = note: No such file or directory (os error 2)

error: could not compile `serde_json` (build script) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
...

Additional information / notes

A whole bunch of results come up when I search issues for environment variables. I can't tell if they're related. There was another issue closed back in 2020 that seems related, but still not sure.

[tgrushka]

Verbose output

It seems there may be 2 issues:

• cross is passing all the CARGO_TARGET_ env vars, even if they are blank. Shouldn't cargo itself ignore them if they are blank? That's a cargo issue, but why is cross passing them if empty?
• cross seems to then confuse the target architectures -- shouldn't it pass only the intended target env vars to cargo?

Without CARGO_TARGET_ env:

cross build --verbose --target aarch64-unknown-linux-gnu
+ cargo metadata --format-version 1 --filter-platform aarch64-unknown-linux-gnu
+ rustc --print sysroot
+ rustup toolchain list
+ rustup target list --toolchain nightly-x86_64-unknown-linux-gnu
+ rustup component list --toolchain nightly-x86_64-unknown-linux-gnu
+ /usr/local/bin/docker
+ /usr/local/bin/docker run --userns host -e 'PKG_CONFIG_ALLOW_CROSS=1' -e 'XARGO_HOME=/xargo' -e 'CARGO_HOME=/cargo' -e 'CARGO_TARGET_DIR=/target' -e 'CROSS_RUNNER=' -e CARGO_REGISTRY_TOKEN -e TERM -e 'USER=tom' --rm --user 1000:1000 -v /home/tom/.xargo:/xargo:z -v /home/tom/.cargo:/cargo:z -v /cargo/bin -v /home/tom/src/cross-test:/project:z -v /home/tom/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu:/rust:z,ro -v /home/tom/src/cross-test/target:/target:z -w /project -i -t ghcr.io/cross-rs/aarch64-unknown-linux-gnu:0.2.5 sh -c 'PATH=$PATH:/rust/bin cargo build --verbose --target aarch64-unknown-linux-gnu'
...

With even blank CARGO_TARGET_ env:

export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=''
export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTFLAGS=''
export CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTC_WRAPPER=''

cross build --verbose --target aarch64-unknown-linux-gnu
+ cargo metadata --format-version 1 --filter-platform aarch64-unknown-linux-gnu
+ rustc --print sysroot
+ rustup toolchain list
+ rustup target list --toolchain nightly-x86_64-unknown-linux-gnu
+ rustup component list --toolchain nightly-x86_64-unknown-linux-gnu
+ /usr/local/bin/docker
+ /usr/local/bin/docker run --userns host -e 'PKG_CONFIG_ALLOW_CROSS=1' -e 'XARGO_HOME=/xargo' -e 'CARGO_HOME=/cargo' -e 'CARGO_TARGET_DIR=/target' -e 'CROSS_RUNNER=' -e CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTC_WRAPPER -e TERM -e CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTFLAGS -e CARGO_REGISTRY_TOKEN -e CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER -e 'USER=tom' --rm --user 1000:1000 -v /home/tom/.xargo:/xargo:z -v /home/tom/.cargo:/cargo:z -v /cargo/bin -v /home/tom/src/cross-test:/project:z -v /home/tom/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu:/rust:z,ro -v /home/tom/src/cross-test/target:/target:z -w /project -i -t ghcr.io/cross-rs/aarch64-unknown-linux-gnu:0.2.5 sh -c 'PATH=$PATH:/rust/bin cargo build --verbose --target aarch64-unknown-linux-gnu'
       Dirty serde v1.0.216: the config settings changed
   Compiling serde v1.0.216
       Dirty serde_json v1.0.134: the config settings changed
   Compiling serde_json v1.0.134
       Fresh ryu v1.0.18
       Fresh itoa v1.0.14
       Fresh memchr v2.7.4
     Running `rustc --crate-name build_script_build --edition=2018 /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/serde-1.0.216/build.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=87 --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="std"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("alloc", "default", "derive", "rc", "serde_derive", "std", "unstable"))' -C metadata=8d6fac6aa058f87e -C extra-filename=-50b94897c7732765 --out-dir /target/debug/build/serde-50b94897c7732765 -C linker= -L dependency=/target/debug/deps --cap-lints allow`
     Running `rustc --crate-name build_script_build --edition=2021 /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/serde_json-1.0.134/build.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=87 --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="std"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("alloc", "arbitrary_precision", "default", "float_roundtrip", "indexmap", "preserve_order", "raw_value", "std", "unbounded_depth"))' -C metadata=08be64cc0f951fa7 -C extra-filename=-c6d6a1facbc9aa6a --out-dir /target/debug/build/serde_json-c6d6a1facbc9aa6a -C linker= -L dependency=/target/debug/deps --cap-lints allow`
error: couldn't extract file stem from specified linker

error: could not compile `serde_json` (build script) due to 1 previous error

Caused by:
  process didn't exit successfully: `rustc --crate-name build_script_build --edition=2021 /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/serde_json-1.0.134/build.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=87 --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="std"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("alloc", "arbitrary_precision", "default", "float_roundtrip", "indexmap", "preserve_order", "raw_value", "std", "unbounded_depth"))' -C metadata=08be64cc0f951fa7 -C extra-filename=-c6d6a1facbc9aa6a --out-dir /target/debug/build/serde_json-c6d6a1facbc9aa6a -C linker= -L dependency=/target/debug/deps --cap-lints allow` (exit status: 1)
warning: build failed, waiting for other jobs to finish...
error: could not compile `serde` (build script) due to 1 previous error

Caused by:
  process didn't exit successfully: `rustc --crate-name build_script_build --edition=2018 /cargo/registry/src/index.crates.io-1949cf8c6b5b557f/serde-1.0.216/build.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --diagnostic-width=87 --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="std"' --check-cfg 'cfg(docsrs,test)' --check-cfg 'cfg(feature, values("alloc", "default", "derive", "rc", "serde_derive", "std", "unstable"))' -C metadata=8d6fac6aa058f87e -C extra-filename=-50b94897c7732765 --out-dir /target/debug/build/serde-50b94897c7732765 -C linker= -L dependency=/target/debug/deps --cap-lints allow` (exit status: 1)
+ rustup component list --toolchain nightly-x86_64-unknown-linux-gnu

[Emilgardis]

This is expected behaviour, the problem is the build scripts target is x86_64-unknown-linux-gnu, and it's the build script binary build that is complaining, not the actual crate binary

error: could not compile serde_json (build script) due to 1 previous error

note (build script) here