From 60aa095ed9af44e5e18778b78454592e9ad61b65 Mon Sep 17 00:00:00 2001
From: Luke Gorrie <luke@snabb.co>
Date: Wed, 15 Mar 2017 13:24:42 +0000
Subject: [PATCH] Specify build dependencies with nix

This adds the file default.nix & instructions for use to README.
---
 README.md   | 29 +++++++++++++++++++++++++++++
 default.nix | 19 +++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 default.nix

diff --git a/README.md b/README.md
index 6d4eafa017..d446a53251 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,35 @@ Initial changes (ongoing work):
 
 PRs welcome! Shock me with your radical ideas! :-)
 
+### Compilation
+
+RaptorJIT is built using GNU Make, Clang (C compiler), and LuaJIT 2 (bootstrap Lua for DynASM etc.) The build environment is specified formally in `default.nix` and can be automatically provided using the [nix](http://nixos.org/nix/) package manager.
+
+Here is how to install nix:
+
+```
+$ curl https://nixos.org/nix/install | sh
+```
+
+Here is how to build raptorjit once nix is installed (note: the first
+compilation takes time to download dependencies):
+
+```shell
+$ nix-build    # produces result/bin/raptorjit
+```
+
+Here is the interactive version:
+
+```
+$ nix-shell    # start sub-shell with pristine build environment in $PATH
+[nix-shell]$ make -j    # build manually as many times as you like
+[nix-shell]$ exit       # quit when done
+```
+
+(You can also skip `nix` and install `clang` and `luajit` yourself if
+you like. The nix approach is future proof to new dependencies and
+allows for pinning specific versions.)
+
 ### Quotes
 
 Here are some borrowed words to put this branch into context:
diff --git a/default.nix b/default.nix
new file mode 100644
index 0000000000..b8081e6303
--- /dev/null
+++ b/default.nix
@@ -0,0 +1,19 @@
+{ pkgs ? (import <nixpkgs> {})
+, source ? ./.
+, version ? "dev"
+}:
+
+with pkgs;
+with clangStdenv;
+
+mkDerivation rec {
+  name = "raptorjit-${version}";
+  inherit version;
+  src = lib.cleanSource source;
+  enableParallelBuilding = true;
+  buildInputs = [ luajit ];
+  installPhase = ''
+    mkdir -p $out/bin
+    cp src/luajit $out/bin/raptorjit
+  '';
+}