commit d433ed913427395adad5088ee4c3a8cd593a2b02
Author: Tobias Berger <toby@tobot.dev>
Date:   Fri Dec 20 16:26:13 2024 +0100

    Initial commit

diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..8392d15
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use flake
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..2bbdbfe
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.direnv
+result
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..89618d2
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,48 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1734424634,
+        "narHash": "sha256-cHar1vqHOOyC7f1+tVycPoWTfKIaqkoe1Q6TnKzuti4=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "d3c42f187194c26d9f0309a8ecc469d6c878ce33",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs",
+        "treefmt-nix": "treefmt-nix"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1734704479,
+        "narHash": "sha256-MMi74+WckoyEWBRcg/oaGRvXC9BVVxDZNRMpL+72wBI=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "65712f5af67234dad91a5a4baee986a8b62dbf8f",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..c50ccb3
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,143 @@
+{
+  description = "An over-engineered Hello World in C";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+
+    treefmt-nix = {
+      url = "github:numtide/treefmt-nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      treefmt-nix,
+    }:
+    let
+      # to work with older version of flakes
+      lastModifiedDate = self.lastModifiedDate or self.lastModified or "19700101";
+
+      # Generate a user-friendly version number.
+      version = builtins.substring 0 8 lastModifiedDate;
+
+      # System types to support.
+      supportedSystems = [
+        "x86_64-linux"
+        "x86_64-darwin"
+        "aarch64-linux"
+        "aarch64-darwin"
+      ];
+
+      forEachSupportedSystem =
+        f:
+        nixpkgs.lib.genAttrs supportedSystems (
+          system:
+          f ({
+            pkgs = import nixpkgs {
+              inherit system;
+              overlays = [ self.overlays.default ];
+            };
+          })
+        );
+    in
+    {
+      formatter = forEachSupportedSystem (
+        { pkgs, ... }: (treefmt-nix.lib.evalModule pkgs ./treefmt.nix).config.build.wrapper
+      );
+      devShells = forEachSupportedSystem (
+        { pkgs, ... }:
+        {
+          default = pkgs.mkShell {
+            nativeBuildInputs = with pkgs; [
+              gcc14
+            ];
+          };
+        }
+      );
+      packages = forEachSupportedSystem (
+        { pkgs, ... }:
+        {
+          default = pkgs.hello;
+        }
+      );
+      overlays.default = final: prev: {
+        hello =
+          with final;
+          gcc14Stdenv.mkDerivation {
+            pname = "main";
+            inherit version;
+
+            src = ./.;
+
+            buildPhase = ''
+              gcc gcc14 --version
+              gcc --std=gnu23 main.c -o main
+            '';
+            installPhase = ''
+              mkdir -p $out/bin
+              install ./main $out/bin
+            '';
+          };
+      };
+
+      nixosModules.hello =
+        { pkgs, ... }:
+        {
+          nixpkgs.overlays = [ self.overlay ];
+
+          environment.systemPackages = [ pkgs.hello ];
+        };
+
+      # Tests run by 'nix flake check' and by Hydra.
+      checks = forEachSupportedSystem (
+        { pkgs, ... }:
+        with pkgs;
+        {
+          inherit (self.packages.${system}) hello;
+
+          # Additional tests, if applicable.
+          test = stdenv.mkDerivation {
+            pname = "hello-test";
+            inherit version;
+
+            buildInputs = [ hello ];
+
+            dontUnpack = true;
+
+            buildPhase = ''
+              echo 'running some integration tests'
+              [[ $(hello) = 'Hello Nixers!' ]]
+            '';
+
+            installPhase = "mkdir -p $out";
+          };
+        }
+        // lib.optionalAttrs gcc14stdenv.isLinux {
+          # A VM test of the NixOS module.
+          vmTest =
+            with import (nixpkgs + "/nixos/lib/testing-python.nix") {
+              inherit system;
+            };
+
+            makeTest {
+              nodes = {
+                client =
+                  { ... }:
+                  {
+                    imports = [ self.nixosModules.hello ];
+                  };
+              };
+
+              testScript = ''
+                start_all()
+                client.wait_for_unit("multi-user.target")
+                client.succeed("hello")
+              '';
+            };
+        }
+      );
+    };
+}
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..dfe19e7
--- /dev/null
+++ b/main.c
@@ -0,0 +1,42 @@
+#include <stdio.h>
+#define Result_t(T, E)                                                         \
+  struct Result_##T##_##E {                                                    \
+    bool is_ok;                                                                \
+    union {                                                                    \
+      T value;                                                                 \
+      E error;                                                                 \
+    };                                                                         \
+  }
+
+#define Ok(T, E)                                                               \
+  (struct Result_##T##_##E) {                                                  \
+    .is_ok = true, .value = (T)_OK_IMPL
+#define _OK_IMPL(...)                                                          \
+  __VA_ARGS__                                                                  \
+  }
+
+#define Err(T, E)                                                              \
+  (struct Result_##T##_##E) {                                                  \
+    .is_ok = false, .error = (E)_ERR_IMPL
+#define _ERR_IMPL(...)                                                         \
+  __VA_ARGS__                                                                  \
+  }
+
+typedef const char *ErrorMessage_t;
+
+Result_t(int, ErrorMessage_t) my_func(int i) {
+  if (i == 42)
+    return Ok(int, ErrorMessage_t)(100);
+  else
+    return Err(int, ErrorMessage_t)("Cannot do the thing");
+}
+
+int main(void) {
+  Result_t(int, ErrorMessage_t) x = my_func(42);
+
+  if (x.is_ok) {
+    printf("%d\n", x.value);
+  } else {
+    printf("%s\n", x.error);
+  }
+}
diff --git a/treefmt.nix b/treefmt.nix
new file mode 100644
index 0000000..ec20712
--- /dev/null
+++ b/treefmt.nix
@@ -0,0 +1,8 @@
+{ ... }:
+{
+  projectRootFile = "flake.nix";
+  programs = {
+    nixfmt.enable = true;
+    clang-format.enable = true;
+  };
+}