Cross compile roslibrust_ros1 to aarch64 (arm64, e.g. a Jetson)?

[lucasw]

Windows/mingw cross compiling works fine like this (though I haven't tested the built .exes much):

rustup target add x86_64-pc-windows-gnu
apt install mingw-w64
cargo build --target x86_64-pc-windows-gnu --release

But what I'm more interested in is cross compiling to arm for use on a Jetson:

rustup target add aarch64-unknown-linux-gnu
apt install gcc-aarch64-linux-gnu

cargo build --target aarch64-unknown-linux-gnu

This fails because of openssl:

warning: openssl-sys@0.9.111: Could not find directory of OpenSSL installation, and this `-sys` crate cannot proceed without this knowledge. If OpenSSL is installed and this crate had trouble finding it,  you can set the `OPENSSL_DIR` environment variable for the compilation process. See stderr section below for further information.
error: failed to run custom build command for `openssl-sys v0.9.111`

Caused by:
  process didn't exit successfully: `.../roslibrust_upstream/target/debug/build/openssl-sys-46b0cda03573f495/build-script-main` (exit status: 101)
  --- stdout
  cargo:rustc-check-cfg=cfg(osslconf, values("OPENSSL_NO_OCB", "OPENSSL_NO_SM4", "OPENSSL_NO_SEED", "OPENSSL_NO_CHACHA", "OPENSSL_NO_CAST", "OPENSSL_NO_IDEA", "OPENSSL_NO_CAMELLIA", "OPENSSL_NO_RC4", "OPENSSL_NO_BF", "OPENSSL_NO_PSK", "OPENSSL_NO_DEPRECATED_3_0", "OPENSSL_NO_SCRYPT", "OPENSSL_NO_SM3", "OPENSSL_NO_RMD160", "OPENSSL_NO_EC2M", "OPENSSL_NO_OCSP", "OPENSSL_NO_CMS", "OPENSSL_NO_COMP", "OPENSSL_NO_SOCK", "OPENSSL_NO_STDIO", "OPENSSL_NO_EC", "OPENSSL_NO_SSL3_METHOD", "OPENSSL_NO_KRB5", "OPENSSL_NO_TLSEXT", "OPENSSL_NO_SRP", "OPENSSL_NO_SRTP", "OPENSSL_NO_RFC3779", "OPENSSL_NO_SHA", "OPENSSL_NO_NEXTPROTONEG", "OPENSSL_NO_ENGINE", "OPENSSL_NO_BUF_FREELISTS", "OPENSSL_NO_RC2"))
  cargo:rustc-check-cfg=cfg(openssl)
  cargo:rustc-check-cfg=cfg(libressl)
...
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR


  Could not find openssl via pkg-config:
  pkg-config has not been configured to support cross-compilation.

  Install a sysroot for the target platform and configure it via
  PKG_CONFIG_SYSROOT_DIR and PKG_CONFIG_PATH, or install a
  cross-compiling wrapper for pkg-config and set it via
  PKG_CONFIG environment variable.

  cargo:warning=Could not find directory of OpenSSL installation, and this `-sys` crate cannot proceed without this knowledge. If OpenSSL is installed and this crate had trouble finding it,  you can set the `OPENSSL_DIR` environment variable for the compilation process. See stderr section below for further information.

  --- stderr


  Could not find directory of OpenSSL installation, and this `-sys` crate cannot
  proceed without this knowledge. If OpenSSL is installed and this crate had
  trouble finding it,  you can set the `OPENSSL_DIR` environment variable for the
  compilation process.

  Make sure you also have the development packages of openssl installed.
  For example, `libssl-dev` on Ubuntu or `openssl-devel` on Fedora.

  If you're in a situation where you think the directory *should* be found
  automatically, please open a bug at https://github.com/rust-openssl/rust-openssl
  and include information about your system as well as this message.

  $HOST = x86_64-unknown-linux-gnu
  $TARGET = aarch64-unknown-linux-gnu
  openssl-sys = 0.9.111

openssl is depended on through reqwest

roslibrust_ros1# cargo tree -i openssl
openssl v0.10.75
`-- native-tls v0.2.14
    |-- hyper-tls v0.5.0
    |   `-- reqwest v0.11.27
    |       `-- roslibrust_ros1 v0.16.0 (.../roslibrust_upstream/roslibrust_ros1)
    |           `-- roslibrust v0.16.0 (/../roslibrust_upstream/roslibrust)
    |               `-- roslibrust_test v0.1.0 (.../roslibrust_upstream/roslibrust_test)
    |                   [dev-dependencies]
    |                   `-- roslibrust_ros1 v0.16.0 (...roslibrust_upstream/roslibrust_ros1) (*)
    |-- reqwest v0.11.27 (*)
    `-- tokio-native-tls v0.3.1
        |-- hyper-tls v0.5.0 (*)
        `-- reqwest v0.11.27 (*)

One route is to make reqwest not use openssl, I think that's like this but there are other options

reqwest = { version = "0.11", default-features = false, features = ["rustls-tls"] }

cargo update maybe is necessary after that

• and that appears to work fine with latest roslibrust (0.16 e8f81f7), but I have an older version of roslibrust (based on v0.12.1) and am getting errors like this:

  = note: /usr/bin/ld: ...roslibrust/target/aarch64-unknown-linux-gnu/debug/deps/roslibrust_ros1-f3f932adb17bfc0f.3dawdu7ydopqmq3t8d4yef6pt.1224mww.rcgu.o: Relocations in generic ELF (EM: 183)
          /usr/bin/ld: .../roslibrust/target/aarch64-unknown-linux-gnu/debug/deps/roslibrust_ros1-f3f932adb17bfc0f.3dawdu7ydopqmq3t8d4yef6pt.1224mww.rcgu.o: Relocations in generic ELF (EM: 183)

I should get updated, though I may spend a few minutes bisecting to see what changed.

(this is all within a debian 13 trixie docker container, but Ubuntu 24.04 had similar issues before I switched to docker)

[lucasw]

It's something between 0.13 and 0.14 -> 9cf4d0b

[Carter12s]

I pushed a demo branch here that successfully cross compiles. Little bit of arcana involved to make everything work.

We could certainly add a feature flag to overall roslibrust to add "vendored" as an option, but honestly this would be a great topic for a page in the book/

[lucasw]

Thanks! I can cross build my project now with that .cargo/config.toml

# Cross-compilation configuration for aarch64-unknown-linux-gnu

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

# Environment variables for OpenSSL vendored build
# These ensure that openssl-sys builds from source with the correct cross-compiler
[target.aarch64-unknown-linux-gnu.env]
CC = "aarch64-linux-gnu-gcc"
CXX = "aarch64-linux-gnu-g++"
AR = "aarch64-linux-gnu-ar"
CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER = "aarch64-linux-gnu-gcc"