Cross-Compiling for Raspberry Pi 2/3/4 servo-fontconfig-sys pkg-config

[nalply]

I am trying to find out if I can develop a Slint application for a Raspberry Pi on an Arch Linux machine.

I copied the Hello World project. I installed the cross-compiling toolchain for arm-none-linux-gnueabihf then entered cargo b. But the build got stopped by crate servo-fontconfig-sys complaining about pkg-config not configured for cross-compilation.

error: failed to run custom build command for `servo-fontconfig-sys v5.1.0`

Caused by:
  process didn't exit successfully: `/home/nalp/Projects/wzu/target/debug/build/servo-fontconfig-sys-9dd4967090b1ee22/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-env-changed=FONTCONFIG_NO_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_armv7-unknown-linux-gnueabihf
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_armv7_unknown_linux_gnueabihf
  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_armv7-unknown-linux-gnueabihf
  cargo:rerun-if-env-changed=PKG_CONFIG_armv7_unknown_linux_gnueabihf
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_armv7-unknown-linux-gnueabihf
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_armv7_unknown_linux_gnueabihf
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR

  --- stderr
  thread 'main' panicked at '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.', /home/nalp/.cargo/registry/src/github.com-1ecc6299db9ec823/servo-fontconfig-sys-5.1.0/build.rs:34:17
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

and I need some help to configure pkg-config correctly.

[tronical]

You can do this, but I recommend using cross to take care of the build environment that has the dependencies. You need fontconfig for host and target.

We have a docker image that you can use with a PI with cross, through Cross.toml:

https://github.com/slint-ui/slint/blob/master/Cross.toml

If you want to test this first in our git repo:

https://github.com/slint-ui/slint/blob/master/docs/building.md#cross-compiling

Edit: Docker files: https://github.com/slint-ui/slint/tree/master/docker

[nalply]

I always wondered why people use such a heavyweight tool like Docker.

This said, I will have a look at cross.

[tronical]

To be honest, I'm also not a fan of Docker. In this case it's just a massive time saver, especially for me as I'm on macOS. With a Linux host, setting up a PI compatible sysroot is indeed much easier and then you don't really need cross - provided you have fontconfig in your sysroot with pkgconfig files as well as in your host environment.

[nalply]

Perhaps, but cross also failed with a pkg-config problem for servo-fontconfig-sys. It seems I need fontconfig with pkg-config files anyway.

Should cross build really work out of the box?

[tronical]

Cross should build out of the box if your Cross.toml is configured to use the same Docker container that we are using (as linked above) as they install fontconfig for host and target, specifically either of these two sections:

[target.aarch64-unknown-linux-gnu]
image = "ghcr.io/slint-ui/slint/aarch64-unknown-linux-gnu"
[target.armv7-unknown-linux-gnueabihf]
image = "ghcr.io/slint-ui/slint/armv7-unknown-linux-gnueabihf"

If you are seeing build issues with these containers, could you paste them here please?

[omdxp]

@tronical I am using Docker image to cross compile with cross on macOS, and got this output:

$ cross build --target=aarch64-unknown-linux-gnu --workspace --exclude slint-node --exclude pyslint --release
...
warning: gobject-sys@0.18.0: pkg-config has not been configured to support cross-compilation.

error: failed to run custom build command for `gobject-sys v0.18.0`

Caused by:
  process didn't exit successfully: `/target/release/build/gobject-sys-6db2c5543bcf944e/build-script-build` (exit status: 1)
  --- stdout
  cargo:rerun-if-env-changed=GOBJECT_2.0_NO_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_aarch64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_aarch64_unknown_linux_gnu
  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-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64_unknown_linux_gnu
  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-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_aarch64_unknown_linux_gnu
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR
  cargo:warning=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.
warning: build failed, waiting for other jobs to finish...
The following warnings were emitted during compilation:

warning: glib-sys@0.18.1: pkg-config has not been configured to support cross-compilation.

error: failed to run custom build command for `glib-sys v0.18.1`

Caused by:
  process didn't exit successfully: `/target/release/build/glib-sys-abee0a9af31a5611/build-script-build` (exit status: 1)
  --- stdout
  cargo:rerun-if-env-changed=GLIB_2.0_NO_PKG_CONFIG
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_aarch64-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_ALLOW_CROSS_aarch64_unknown_linux_gnu
  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-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_aarch64_unknown_linux_gnu
  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-unknown-linux-gnu
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR_aarch64_unknown_linux_gnu
  cargo:rerun-if-env-changed=TARGET_PKG_CONFIG_SYSROOT_DIR
  cargo:rerun-if-env-changed=PKG_CONFIG_SYSROOT_DIR
  cargo:warning=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.

[tronical]

Hi! It looks like you're trying to run cross build on the Slint repository, in a way that it will try to build all projects. One of them that fails is one that needs libraries that aren't present in the docker images. I suggest to either select an example that works (for example -p printerdemo) or perhaps you'd like to use the Cross.toml file with a specific project of your own?