This is probably a bit of a niche use-case that is not well-supported, as I understand, but I wanted to work on a small haskell application for my e-book reader, for which I would have to target a 32-bit ARM architecture.
I was using haskell.nix for cross compilation in different variants (including fully statically linked builds against glibc and musl and a dynamically linked build where I would deploy all dynamic dependencies onto the device). I have had varying degrees of success with this. For example, computing fibonacci numbers and printing out the results was working fine. However, as soon as I introduced some code interacting with the filesystem, the stuff got a bit wonky. For example, when I am having the equivalent of readFile "SomeExistingFile" >>= putStrLn in my file, the output would be just the name of my executable, I guess, followed by a colon.
Originally, I aimed for making some syscalls via FFI (which work locally and also when I cross-compile a similar C program for my reader), but the syscalls return weird stuff (like open returning -1, even though it returns a valid file descriptor in the equivalent C code).
For now, I have failed to set up a cross-compiler toolchain for anything newer than GHC 9.2.8 (haven’t tested with GHC 9.4.x yet), but my basic setup is the following haskell.nix-based flake, sorry it is a bit messy:
My flake.nix
inputs.haskellNix.url = "./haskell.nix";
inputs.nixpkgs.follows = "haskellNix/nixpkgs-unstable";
inputs.flake-utils.url = "github:numtide/flake-utils";
outputs = { self, nixpkgs, flake-utils, haskellNix }:
let
supportedSystems = [
"x86_64-linux"
];
in
flake-utils.lib.eachSystem supportedSystems (system:
let
drv' = pkgs': extraModules:
let
isCrossStatic = pkgs'.stdenv.hostPlatform != pkgs.stdenv.hostPlatform;
in pkgs'.haskell-nix.project {
src = ./.;
compiler-nix-name = (if isCrossStatic then "ghc928" else "ghc964");
modules = [
{
packages.koboworld.components.exes.koboworld =
let p = nixpkgs.lib.strings.makeSearchPath "include" (with pkgs'; [
linuxHeaders
]);
in {
configureFlags = ["--extra-include-dirs=${p}"];
};
}]
++ (if isCrossStatic then
[{
packages.koboworld.components.exes.koboworld = {
configureFlags = [
"--disable-executable-dynamic"
"--disable-shared"
"--ghc-option=-optl-pthread"
"--ghc-option=-optl-static"
"--ghc-option=-optl-lffi"
"--ghc-option=-optl-lnuma"
"--ghc-option=-optl-lgmp"
"--ghc-option=-optl-lz"
"--disable-executable-stripping"
"--disable-library-stripping"
] ++ map (l: "--ghc-option=-optl=-L${l}/lib") (with pkgs'; [
gmp6
zlib
libffi
numactl
]);
};
}]
else [])
++ extraModules;
shell.tools = {
cabal = {};
} // (if isCrossStatic then {} else {
hlint = {};
haskell-language-server = {};
});
};
drv = pkgs': drv' pkgs' [];
pkgs = haskellNix.legacyPackages.${system};
pkgsArm = haskellNix.legacyPackages.${system}.pkgsCross.armv7l-hf-multiplatform.pkgsMusl;
in {
p = (drv pkgs);
packages = {
"exe:koboworld" = (drv pkgs).koboworld.components.exes.koboworld;
"armv7l-hf-multiplatform:exe:koboworld" = (drv pkgsArm).koboworld.components.exes.koboworld;
};
devShells = {
default = (drv pkgs).shell;
};
}
);
}```
For the musl-based build I built GHC with ld.gold, even though this is disabled in haskelll.nix, but since the referenced ld.gold bug is fixed, I still wanted to give it a try. The behaviour, I have described above, however, is the same as if I do a dynamically linked build against glibc and deploy all dependencies onto the device (or a statically linked one against glibc, I think, but I can’t confirm this easily anymore right now and this does not seem to be super-safe?).
Before I give up on this foolish undertaking, I wanted to ask whether any of you has any hints on how I could possibly proceed?
Any help is appreciated!