Cross-compiling

2021-05-29T01:45:40Z

Theintern:

The Pinephone's triple for cross-compiling is aarch64-unknown-linux-gnu.

= Rust =
In order to cross-compile Rust applications for the Pinephone, you need to have a gcc cross-compiler installed and the Rust dependencies, usually the std crate, cross compiled for the target system. A more extensive explanation can be found on https://github.com/japaric/rust-cross. This instruction is based on it's description.

== Installing gcc cross-compiler ==
The cross-compiler might have a different name depending on the operating system. Further along this instruction the name for the gcc cross-compiler will be used. Replace all occurences of $gcc_name with the name on your distribution.
Under Arch Linux the cross-compilers name is aarch64-linux-gnu-gcc and it can be installed with:
$ sudo pacman -S aarch64-linux-gnu-gcc

Ubuntu:
$ sudo apt install gcc-aarch64-linux-gnu

Other distributions:
Please add

== Installing Rust dependencies ==

The necessary dependencies can easily be installed with rustup:
$ rustup target add aarch64-unknown-linux-gnu
OR it can be installed with multirust [Is this still accurate???]:
$ multirust add-target nightly aarch64-unknown-linux-gnu

== Compiling ==

=== rustc ===

When using rustc just add the two flags --target=aarch64-unknown-linux-gnu and -C linker=$gcc_name. Under Arch, this would look like:
$ rustc --target=aarch64-unknown-linux-gnu -C linker=aarch64-linux-gnu-gcc main.rs

To test it, run the program on your Pinephone

$ scp main user@ipadress:/home/user/Downloads
$ ssh user@ipadress /home/user/Downloads/main
Hello, world!

=== cargo ===
To cross-compile a project with cargo, open the folder of the project in a terminal. Then create a new folder and a file for cargo.
$ mkdir .cargo
$ cat >.cargo/config <<EOF
> [target.aarch64-unknown-linux-gnu]
> linker = "$gcc_name"
> EOF
Then you can compile it with
$ cargo build --target=aarch64-unknown-linux-gnu

To test it, copy the file on your Pinephone
$ scp target/aarch64-unknown-linux-gnu/debug/main user@ipadress:/home/user/Downloads
Then you can execute it by
$ ssh user@ipadress ./main -h
Hello, world!

== Possible errors ==
If you encounter an error saying
Cross compilation detected. Use PKG_CONFIG_ALLOW_CROSS=1 to override
just add that variable in front of your command e.g.
PKG_CONFIG_ALLOW_CROSS=1 cargo build --target=aarch64-unknown-linux-gnu

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Cross-compiling