Error with -ludev when cross compiling for ARMv7

[vicdoja]

• Parity Ethereum version: 2.2.7

• Operating system: Linux

• Installation: built from source

• Description: When I try to cross-compile the source for Raspberry Pi (armv7), I get an error saying that "-ludev" couldn't be found. This error occurs at the very end of the compiling process

• Expected behavior: The binaries get built correctly and work on a Raspberry Pi

• Actual behavior: The compilation process ends with an error

Compiling parity-ethereum v2.2.7 (/home/thevidoja/Desktop/parity-ethereum-2.2.7)
Building [=====================================================> ] 490/491: parity(bin)
error: linking with arm-linux-gnueabihf-gcc failed: exit code: 1
  |
  = note: "arm-linux-gnueabihf-gcc" "-Wl,--as-needed" 
...
 "/home/thevidoja/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/armv7-unknown-linux-gnueabihf/lib/libcompiler_builtins-d0572f7a936161bf.rlib" "-Wl,-Bdynamic" "-ludev" "-lstdc++" "-lstdc++" "-lutil" "-lutil" "-ldl" "-lrt" "-lpthread" "-lgcc_s" "-lc" "-lm" "-lrt" "-lpthread" "-lutil" "-lutil"
  = note: /usr/lib/gcc-cross/arm-linux-gnueabihf/7/../../../../arm-linux-gnueabihf/bin/ld: cannot find -ludev
          collect2: error: ld returned 1 exit status
          

error: aborting due to previous error

error: Could not compile parity-ethereum.

To learn more, run the command again with --verbose.

The actual output is much longer, so I attached it as a file.
output.txt

• Steps to reproduce: cargo build --release --features final --target=armv7-unknown-linux-gnueabihf

[jam10o-new]

According to #9750, this error is caused by a missing/misplaced libudev dependency (which might be libudev-dev in your package repository)

[vicdoja]

According to #9750, this error is caused by a missing/misplaced libudev dependency (which might be libudev-dev in your package repository)

The package libudev-dev is already installed on the system, because there was a previous error that got fixed by installing it.
So what should I do to fix this issue if I already installed it?
My experience with cross compiling and compiling from sources is kind of limited and I don't really know how to fix it.

[jam10o-new]

@TheVidoja here's all the dependencies afaict, you can probably just run these commands:

https://github.com/paritytech/parity-ethereum/blob/0bfd5bacafc8914405c16454eb386737e2d2ea8a/scripts/docker/ubuntu-aarch64/Dockerfile#L19-L25

Since you're cross compiling, you need the library for the architecture you're compiling to as well.

[vicdoja]

@joshua-mir when I try and install the armhf library this happens:

sudo apt install libudev-dev:armhf
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package libudev-dev:armhf is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  libudev-dev libudev-dev:i386

E: Package 'libudev-dev:armhf' has no installation candidate

I don't really know where to go from here.

[jam10o-new]

@TheVidoja from earlier in the dockerfile I linked above, you need to add source URLs for the architecture you're compiling to

[niklasad1]

@TheVidoja

I think you want this package (might a different track) if it works otherwise I think you need build it from source as @joshua-mir suggested.

However, I now see that our docker image is broken for ubuntu arm which we need to fix!

[niklasad1]

libudev is not required anymore after hardware wallet support was removed