Rustc cross-compiling to aarch64-unknown-linux-gnu uses wrong compiler

[ghost]

Cross compiling from x86_64 to aarch64 uses /usr/bin/ld instead of /usr/bin/aarch64-linux-gnu-ld
This happens using stable and nightly version of rust toolchians/targets

Code

any simple code

fn main() {
    println!("a message");
}

Meta

rustc --version --verbose:

rustc 1.52.0-nightly (a15f484b9 2021-02-22)
binary: rustc
commit-hash: a15f484b918a4533ad633ea903ccce82910af342
commit-date: 2021-02-22
host: x86_64-unknown-linux-gnu
release: 1.52.0-nightly
LLVM version: 11.0.1

Error output

RUST_BACKTRACE=1 cargo build --target aarch64-unknown-linux-gnu

  = note: /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: /home/avery/Documents/git/plage/target/aarch64-unknown-linux-gnu/debug/deps/plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: error adding symbols: file in wrong format
          collect2: error: ld returned 1 exit status

file plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o

plage-7843fadef320354a.1115kt21cxrb61jx.rcgu.o: ELF 64-bit LSB relocatable, ARM aarch64, version 1 (SYSV), with debug_info, not stripped

[ghost]

The issue comes from it using the wrong cc compiler. It prints out a very long command before the errors using "cc", copying it and changing cc to aarch64-linux-gnu-gcc works without any errors. This means rustc is calling the wrong compiler.

[nagisa]

Ah, my bad, I missed that this is not about rustbuild, but about using rustc in crosscompiling regular programs.

As far as I know there are no such heuristics when invoking plain rustc. It is a responsibility of the user to specify the linkers etc to use (via e.g. -Clinker when invoking rustc directly and via corresponding configuration in cargo when building via cargo).

[ghost]

  [target.aarch64-unknown-linux-gnu]
  linker = "aarch64-linux-gnu-ld"

cargo +nightly b --target aarch64-unknown-linux-gnu

still uses the incorrect compiler and linker (cc & /usr/bin/ld)

[nagisa]

That would mean its either a bug in cargo, or cargo can't find your cargo config (as documented here). Where did you put the file with these contents?

Another caveat is that you want to use aarch64-linux-gnu-cc as your linker, rather than the bare ld – there is a way to use ld (-Clinker-flavor=ld), but by default we rely on cc to do the job of finding the libraries, etc.

[ghost]

Cargo.toml works now. Thank you for the help.