How do I cross compile my own package (rather than something in nix-pkgs)

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1

The cross compilation tutorials all have examples of how to use nix to cross compile packages in nixpkgs, but I cannot find one on how to cross compile my own package. I have the following default.nix.

{ pkgs ? import <nixpkgs> {} }:
   pkgs.stdenv.mkDerivation {
     name = "atest";
     src = ./src;

     buildInputs = [
       pkgs.SDL2
       pkgs.SDL2.dev
     ];

     buildPhase = ''
     gcc -o example main.c -lSDL2
     '';

     installPhase = ''
       mkdir -p $out
       cp example $out/
     '';
    }

and in src/main.c I have

#include <SDL2/SDL.h>

int main(int arc, char ** argv) {
    if (SDL_Init( SDL_INIT_VIDEO ) < 0) {
        printf("SDL could not initialize!\n");
    } else {
        SDL_CreateWindow(
            "SDL2 Demo",
            SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
            800, 600,
            SDL_WINDOW_SHOWN
        );

        SDL_Delay(2000);
    }

    return 0;
}

If I type nix-build it builds without problem for linux, but I cannot figure out how to cross compile this for windows (mingw) with nix.

2

First you need to separate your nix file in two files, one that does callPackage on the other:
default.nix:

{ pkgs ? import <nixpkgs> {} }:
   pkgs.callPackage ./myapp.nix {}

and ./myapp.nix:

{ stdenv, SDL2 }: mkDerivation { ... }

Then check that it still builds. Then to cross compile, replace usage of pkgs.callPackage by pkgs.pkgsCross.mingw64.callPackage.

Good luck :slight_smile:

5 Likes
3

Thanks, that solves it!