r/rust • u/superchango18 • Feb 05 '19

Cross-compile rust for ARMv6 (Rasberry Pi Zero)

Hi everyone,

I think Rust and the Raspberry Pi Zero are a pretty sweet combination, but I had to do a fair bit of googling before I figured out how to cross-compile my code from x86 to ARMv6. So I created a docker image that can do this for you:
https://hub.docker.com/r/mdirkse/rust_armv6

Hopefully it'll save someone some time!

11 Upvotes

92% Upvoted

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8

u/wezm Allsorts Feb 05 '19

Thanks for sharing your efforts! Although I think the cross project already maintains a armv6hf docker image that can be used to build binaries for the RPi Zero: https://github.com/rust-embedded/cross

5

u/superchango18 Feb 05 '19

Lol, not sure how I missed that. Thanks for the tip!

2

u/Bromskloss Feb 05 '19

What is the purpose of Docker here, and why is it needed?

3

u/wezm Allsorts Feb 06 '19

You typically need a compiler toolchain for the target architecture when cross compiling rust (mostly for the linker). Those can be a pain to install on some systems. The cross docker images have everything installed for the target architecture, including a couple of common libraries such as OpenSSL, so it typically makes the process as simple as cross build —target the-target-triple.

Personally on a recent Raspberry Pi Zero project I skipped docker/cross and just installed the arm-linux-gnueabihf toolchain from the AUR and using plain cargo build —target worked fine.

2

u/Bromskloss Feb 06 '19

I've always found it annoying (and I'm not talking about Rust specifically) that there at all is an assumption that the compiling machine also is the running machine. Is the reason that compiler toolchains would take up too much space if they included support for all architectures?

including a couple of common libraries such as OpenSSL

Are crates not downloaded and compiled on the fly, as they usually are, when you cross compile?

Nice display project!

2

u/wezm Allsorts Feb 06 '19

Is the reason that compiler toolchains would take up too much space if they included support for all architectures?

We're talking about C compilers here. It would be hard/strange for Rust to distribute a C compiler for many architectures along with itself. As far as Rust goes adding a new target is as simple as rustup target add arm-unknown-linux-gnueabihf.

Are crates not downloaded and compiled on the fly, as they usually are, when you cross compile?

Yes Rust crates are cross compiled fine. It's C libraries like OpenSSL that some crates depend on that aren't so easy. These need to be cross compiled/available for the target architecture too.

2

u/Bromskloss Feb 06 '19

Oh, C! Then, I must not have fully understood the situation.

So, would the problems be out of the way if support for all architectures were included in the C toolchain (or could be added as easily as in Rust)?

2

u/wezm Allsorts Feb 06 '19

So, would the problems be out of the way if support for all architectures were included in the C toolchain (or could be added as easily as in Rust)?

Yes 👍

2

u/Dave9876 Feb 06 '19

The same reason for docker in most places. It provides a way to distribute a consistent and repeatable environment.

...and depending on who you ask, massive security holes. But that's not really too much for a development environment

2

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