Got windows cross-compilation working

The resulting binary is still untested, but it _does_ compile!

This required re-jiggering basically everything about the nix flake,
including replacing the toolchain management to fenix.

flake.lock

@@ -1,26 +1,27 @@
 {
   "nodes": {
-    "flake-utils": {
+    "fenix": {
       "inputs": {
-        "systems": "systems"
+        "nixpkgs": "nixpkgs",
+        "rust-analyzer-src": "rust-analyzer-src"
       },
       "locked": {
-        "lastModified": 1681202837,
+        "lastModified": 1699770036,
-        "narHash": "sha256-H+Rh19JDwRtpVPAWp64F+rlEtxUWBAQW28eAi3SRSzg=",
+        "narHash": "sha256-bZmI7ytPAYLpyFNgj5xirDkKuAniOkj1xHdv5aIJ5GM=",
-        "owner": "numtide",
+        "owner": "nix-community",
-        "repo": "flake-utils",
+        "repo": "fenix",
-        "rev": "cfacdce06f30d2b68473a46042957675eebb3401",
+        "rev": "81ab0b4f7ae9ebb57daa0edf119c4891806e4d3a",
         "type": "github"
       },
       "original": {
-        "owner": "numtide",
+        "owner": "nix-community",
-        "repo": "flake-utils",
+        "repo": "fenix",
         "type": "github"
       }
     },
     "naersk": {
       "inputs": {
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs_2"
       },
       "locked": {
         "lastModified": 1690373729,
@@ -38,6 +39,22 @@
       }
     },
     "nixpkgs": {
+      "locked": {
+        "lastModified": 1699099776,
+        "narHash": "sha256-X09iKJ27mGsGambGfkKzqvw5esP1L/Rf8H3u3fCqIiU=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "85f1ba3e51676fa8cc604a3d863d729026a6b8eb",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
       "locked": {
         "lastModified": 1691003216,
         "narHash": "sha256-Qq/MPkhS12Bl0X060pPvX3v9ac3f2rRQfHjjozPh/Qs=",
@@ -51,7 +68,7 @@
         "type": "indirect"
       }
     },
-    "nixpkgs_2": {
+    "nixpkgs_3": {
       "locked": {
         "lastModified": 1688392541,
         "narHash": "sha256-lHrKvEkCPTUO+7tPfjIcb7Trk6k31rz18vkyqmkeJfY=",
@@ -67,94 +84,27 @@
         "type": "github"
       }
     },
-    "nixpkgs_3": {
-      "locked": {
-        "lastModified": 1681358109,
-        "narHash": "sha256-eKyxW4OohHQx9Urxi7TQlFBTDWII+F+x2hklDOQPB50=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "96ba1c52e54e74c3197f4d43026b3f3d92e83ff9",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "ref": "nixpkgs-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
     "root": {
       "inputs": {
+        "fenix": "fenix",
         "naersk": "naersk",
-        "nixpkgs": "nixpkgs_2",
-        "rust-overlay": "rust-overlay",
-        "utils": "utils"
-      }
-    },
-    "rust-overlay": {
-      "inputs": {
-        "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs_3"
-      },
-      "locked": {
-        "lastModified": 1691029059,
-        "narHash": "sha256-QwVeE9YTgH3LmL7yw2V/hgswL6yorIvYSp4YGI8lZYM=",
-        "owner": "oxalica",
-        "repo": "rust-overlay",
-        "rev": "99df4908445be37ddb2d332580365fce512a7dcf",
-        "type": "github"
-      },
-      "original": {
-        "owner": "oxalica",
-        "repo": "rust-overlay",
-        "type": "github"
       }
     },
-    "systems": {
+    "rust-analyzer-src": {
+      "flake": false,
       "locked": {
-        "lastModified": 1681028828,
+        "lastModified": 1699715108,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "narHash": "sha256-yPozsobJU55gj+szgo4Lpcg1lHvGQYAT6Y4MrC80mWE=",
-        "owner": "nix-systems",
+        "owner": "rust-lang",
-        "repo": "default",
+        "repo": "rust-analyzer",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "rev": "5fcf5289e726785d20d3aa4d13d90a43ed248e83",
         "type": "github"
       },
       "original": {
-        "owner": "nix-systems",
+        "owner": "rust-lang",
-        "repo": "default",
+        "ref": "nightly",
-        "type": "github"
+        "repo": "rust-analyzer",
-      }
-    },
-    "systems_2": {
-      "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
-      }
-    },
-    "utils": {
-      "inputs": {
-        "systems": "systems_2"
-      },
-      "locked": {
-        "lastModified": 1689068808,
-        "narHash": "sha256-6ixXo3wt24N/melDWjq70UuHQLxGV8jZvooRanIHXw0=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "919d646de7be200f3bf08cb76ae1f09402b6f9b4",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
         "type": "github"
       }
     }

flake.nix

@@ -1,102 +1,143 @@
 {
   inputs = {
+    fenix.url = "github:nix-community/fenix";
     naersk.url = "github:nix-community/naersk/master";
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.11";
-    utils.url = "github:numtide/flake-utils";
-
-    rust-overlay.url = "github:oxalica/rust-overlay";
   };
 
-  outputs = { self, nixpkgs, utils, naersk, rust-overlay }:
+  outputs = { self, nixpkgs, naersk, fenix }:
     let
-      buildTargetsBySystem = {
+      buildTargets = {
-        "x86_64-linux" = "x86_64-unknown-linux-musl";
+        "x86_64-linux" = {
-        "i686-linux" = "i686-unknown-linux-musl";
+          crossSystemConfig = "x86_64-unknown-linux-musl";
-        "aarch64-linux" = "aarch64-unknown-linux-musl";
+          rustTarget = "x86_64-unknown-linux-musl";
         };
 
-      supportedSystems = builtins.attrNames buildTargetsBySystem;
+        "i686-linux" = {
+          crossSystemConfig = "i686-unknown-linux-musl";
+          rustTarget = "i686-unknown-linux-musl";
+        };
 
-      eachCrossSystem = callback: (builtins.foldl'
+        "aarch64-linux" = {
-        (overall: buildSystem: overall // {
+          crossSystemConfig = "aarch64-unknown-linux-musl";
-          ${buildSystem} = (builtins.foldl'
+          rustTarget = "aarch64-unknown-linux-musl";
-            (inner: hostSystem: inner // {
+        };
-              "cross-${hostSystem}" = callback buildSystem hostSystem;
+
+        "x86_64-windows" = {
+          crossSystemConfig = "x86_64-w64-mingw32";
+          rustTarget = "x86_64-pc-windows-gnu";
+          makeBuildPackageAttrs = pkgsCross: {
+            depsBuildBuild = [
+              pkgsCross.stdenv.cc
+              pkgsCross.windows.pthreads
+            ];
+          };
+        };
+      };
+
+      # eachSystem [system] (system: ...)
+      #
+      # Returns an attrset with a key for every system in the given array, with
+      # the key's value being the result of calling the callback with that key.
+      eachSystem = supportedSystems: callback: builtins.foldl'
+        (overall: system: overall // { ${system} = callback system; })
+        {}
+        supportedSystems;
+
+      # eachCrossSystem [system] (buildSystem: targetSystem: ...)
+      #
+      # Returns an attrset with a key "$buildSystem.cross-$targetSystem" for
+      # every combination of the elements of the array of system strings. The
+      # value of the attrs will be the result of calling the callback with each
+      # combination.
+      #
+      # There will also be keys "$system.default", which are aliases of
+      # "$system.cross-$system" for every system.
+      #
+      eachCrossSystem = supportedSystems: callback:
+        eachSystem supportedSystems (buildSystem: builtins.foldl'
+            (inner: targetSystem: inner // {
+              "cross-${targetSystem}" = callback buildSystem targetSystem;
             })
             { default = callback buildSystem buildSystem; }
             supportedSystems
         );
-        })
-        {}
-        supportedSystems
-      );
 
-      mkPkgs = buildSystem: hostSystem: import nixpkgs ({
+      mkPkgs = buildSystem: targetSystem: import nixpkgs ({
         system = buildSystem;
-        overlays = [
+      } // (if targetSystem == null then {} else {
-          (import rust-overlay)
-          (final: prev: {
-            rust-toolchain = prev.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
-          })
-        ];
-      } // (if buildSystem == hostSystem then {} else {
         # The nixpkgs cache doesn't have any packages where cross-compiling has
         # been enabled, even if the target platform is actually the same as the
         # build platform (and therefore it's not really cross-compiling). So we
         # only set up the cross-compiling config if the target platform is
         # different.
-        crossSystem.config = hostSystem;
+        crossSystem.config = buildTargets.${targetSystem}.crossSystemConfig;
       }));
 
-      mkRustEnv = crossPkgs: hostSystem: {
+    in {
+      packages = eachCrossSystem
+        (builtins.attrNames buildTargets)
+        (buildSystem: targetSystem: let
+          pkgs = mkPkgs buildSystem null;
+          pkgsCross = mkPkgs buildSystem targetSystem;
+          rustTarget = buildTargets.${targetSystem}.rustTarget;
+
+          # TODO I'd prefer to use the toolchain file
+          # https://github.com/nix-community/fenix/issues/123
+          #toolchain = fenix.packages.${buildSystem}.fromToolchainFile {
+          #  file = ./rust-toolchain.toml;
+          #  sha256 = "sha256-LU4C/i+maIOqBZagUaXpFyWZyOVfQ3Ah5/JTz7v6CG4=";
+          #};
+
+          fenixPkgs = fenix.packages.${buildSystem};
+
+          mkToolchain = fenixPkgs: fenixPkgs.toolchainOf {
+            channel = "nightly";
+            date = "2023-07-23";
+            sha256 = "sha256-LU4C/i+maIOqBZagUaXpFyWZyOVfQ3Ah5/JTz7v6CG4=";
+          };
+
+          toolchain = fenixPkgs.combine [
+            (mkToolchain fenixPkgs).rustc
+            (mkToolchain fenixPkgs).cargo
+            (mkToolchain fenixPkgs.targets.${rustTarget}).rust-std
+          ];
+
+          buildPackageAttrs = if
+            builtins.hasAttr "makeBuildPackageAttrs" buildTargets.${targetSystem}
+          then
+            buildTargets.${targetSystem}.makeBuildPackageAttrs pkgsCross
+          else
+            {};
+
+          naersk-lib = pkgs.callPackage naersk {
+            cargo = toolchain;
+            rustc = toolchain;
+          };
+
+        in
+          naersk-lib.buildPackage (buildPackageAttrs // rec {
+            src = ./.;
+            strictDeps = true;
+            doCheck = false;
+
             OPENSSL_STATIC = "1";
-        OPENSSL_LIB_DIR = "${crossPkgs.pkgsStatic.openssl.out}/lib";
+            OPENSSL_LIB_DIR = "${pkgsCross.pkgsStatic.openssl.out}/lib";
-        OPENSSL_INCLUDE_DIR = "${crossPkgs.pkgsStatic.openssl.dev}/include";
+            OPENSSL_INCLUDE_DIR = "${pkgsCross.pkgsStatic.openssl.dev}/include";
-        CARGO_BUILD_TARGET = buildTargetsBySystem.${hostSystem};
+
+            # Required because ring crate is special. This also seems to have
+            # fixed some issues with the x86_64-windows cross-compile :shrug:
+            TARGET_CC="${pkgsCross.stdenv.cc}/bin/${pkgsCross.stdenv.cc.targetPrefix}cc";
+
+            CARGO_BUILD_TARGET = rustTarget;
             CARGO_BUILD_RUSTFLAGS = [
               "-C" "target-feature=+crt-static"
-          "-C" "linker=${crossPkgs.stdenv.cc}/bin/${crossPkgs.stdenv.cc.targetPrefix}cc"
               "-C" "link-arg=-static"
-        ];
-      };
 
-    in
+              # https://github.com/rust-lang/cargo/issues/4133
-    {
+              "-C" "linker=${TARGET_CC}"
-      packages = eachCrossSystem (buildSystem: hostSystem: let
+            ];
-        pkgs = mkPkgs buildSystem buildSystem;
+          })
-        crossPkgs = mkPkgs buildSystem hostSystem;
-        naersk-lib = pkgs.callPackage naersk {
-          cargo = pkgs.rust-toolchain;
-          rustc = pkgs.rust-toolchain;
-        };
-        rustEnv = mkRustEnv crossPkgs hostSystem;
-      in
-        naersk-lib.buildPackage ({
-          src = ./.;
-          doCheck = false;
-          nativeBuildInputs = [ crossPkgs.pkgsStatic.stdenv.cc ];
-        } // rustEnv)
         );
-
-      devShells = eachCrossSystem (buildSystem: hostSystem: let
-        pkgs = mkPkgs buildSystem buildSystem;
-        crossPkgs = mkPkgs buildSystem hostSystem;
-        rustEnv = mkRustEnv crossPkgs hostSystem;
-      in
-        pkgs.mkShell ({
-          nativeBuildInputs = [
-            crossPkgs.stdenv.cc
-            crossPkgs.openssl
-            pkgs.nmap # ncat
-            pkgs.rust-toolchain
-          ];
-          shellHook = ''
-            export CARGO_HOME=$(pwd)/.cargo
-
-            if [ -f "config.yml" ]; then
-              export DOMANI_CONFIG_PATH=config-dev.yml
-            fi
-          '';
-        } // rustEnv));
     };
 }

rust-toolchain.toml

@@ -4,5 +4,6 @@ components = [ "rustfmt", "rustc-dev", "clippy", "cargo" ]
 targets = [
     "x86_64-unknown-linux-musl",
     "i686-unknown-linux-musl",
-    "aarch64-unknown-linux-musl"
+    "aarch64-unknown-linux-musl",
+    "x86_64-pc-windows-gnu"
 ]