Mulitple issues compiling for arm-unknown-linux-gnueabihf (armv6hf)

[Trayshar]

Checklist

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

Describe your issue

I have multiple issues compiling for arm-unknown-linux-gnueabihf. Building my project yields

thread 'main' panicked at 'Unable to find libudev: Failure { command: "\"pkg-config\" \"--libs\" \"--cflags\" \"libudev\"", output: Output { status: ExitStatus(ExitStatus(256)), stdout: "", stderr: "Package libudev was not found in the pkg-config search path.\nPerhaps you should add the directory containing libudev.pc into the PKG_CONFIG_PATH environment variable\nNo package \'libudev\' found\n" } }'

libudev-dev is installed correctly inside the image. Re-adding the lineENV PKG_CONFIG_PATH="/usr/lib/arm-linux-gnueabihf/pkgconfig/:${PKG_CONFIG_PATH}" that was removed in #734 to my own Dockerfile fixes this for me, but leaves me with another error:

warning: etc/hidapi/linux/hid.c:44:10: fatal error: libudev.h: No such file or directory
warning:  #include <libudev.h>
warning:           ^~~~~~~~~~~
warning: compilation terminated.

I solved this by copying the header file into /x-tools/arm-unknown-linux-gnueabihf/arm-unknown-linux-gnueabihf/sysroot/usr/include/libudev.h. I believe that this is not a good solution. Is there a way to fix this in the base dockerfile itself?

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

aarch64-unknown-linux-gnu, arm-unknown-linux-gnueabihf, armv7-unknown-linux-gnueabihf, i686-unknown-linux-gnu, x86_64-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 0.22.0

Example

No response

Additional information / notes

All other architectures(armv7, aarch64, i686, x86) build without issues with just some commands to install "libudev-dev" in the pre-built section of my Cross.toml file, e.g.:

[target.armv7-unknown-linux-gnueabihf]
pre-build = [
    "dpkg --add-architecture armhf",
    "apt-get update",
    "apt-get install -y libudev-dev:armhf"
]

[Trayshar]

Another, related question (which I originally had inside this issue) was split into #875

[Alexhuszagh]

Since this is the only crosstool-ng-based image among these, it might due to the include search directories being different to obviously avoid including headers for the host architecture. There should be a fairly easy way to ensure that any Debian packages installed use are found by crosstool-ng. You can also technically override CFLAGS_${TARGET} and just had -I /path/to/header/dir, but that should be something that we handle.

[Trayshar]

What about the first part with PKG_CONFIG_PATH not being set? I'd say that's a bug (maybe I should've split this issue in two?)

[Alexhuszagh]

Let me quickly verify why I didn't set it (I think I was worried because the default version compiled for ARMv7 so I was worried the system libraries would also be the same, so I intentionally removed it), but I can go back and check the architecture data via readelf just to ensure. This image was patched because it originally and incorrectly targeted ARMv7.

[Alexhuszagh]

My fears were correct: I believe you'll have to build any packages from source (or even better, use vcpkg or Conan. Maybe this is also worth a Wiki entry? I did this extensively in my C++ port of cross, so it should be trivial to document. Yes, I like cross enough to maintain a spiritual port for a different language.

$ readelf -A ./lib/arm-linux-gnueabihf/libudev.so
Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "7-A"
  Tag_CPU_arch: v7
  Tag_CPU_arch_profile: Application
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-2
  Tag_FP_arch: VFPv3-D16
  Tag_ABI_PCS_wchar_t: 4
  Tag_ABI_FP_rounding: Needed
  Tag_ABI_FP_denormal: Needed
  Tag_ABI_FP_exceptions: Needed
  Tag_ABI_FP_number_model: IEEE 754
  Tag_ABI_align_needed: 8-byte
  Tag_ABI_align_preserved: 8-byte, except leaf SP
  Tag_ABI_enum_size: int
  Tag_ABI_VFP_args: VFP registers
  Tag_CPU_unaligned_access: v6

So just using the system packages won't work here.

[Alexhuszagh]

I've since documented using vcpkg, Meson, and Conan on the Wiki, and created a sample project using them. It still needs a little bit of work so it uses CMake and Meson rust-bindings to integrate better into build systems rather than building binaries, but the general documentation and working samples are there.