Add Nix flake

README.md

@@ -105,6 +105,10 @@ In order to optimize support effort,
 		brew install cmake ninja openssl@3 wget doxygen graphviz astyle valgrind
 		pip3 install pytest pytest-xdist pyyaml
 
+	Using Nix:
+
+	    nix develop
+
 	Note that, if you want liboqs to use OpenSSL for various symmetric crypto algorithms (AES, SHA-2, etc.) then you must have OpenSSL installed (version 3.x recommended; EOL version 1.1.1 also still possible).
 
 2. Get the source:

flake.nix

@@ -0,0 +1,87 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-24.05";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+  outputs = {
+    self,
+    nixpkgs,
+    flake-utils,
+  }:
+    flake-utils.lib.eachDefaultSystem (system: let
+      name = "liboqs";
+      src = ./.;
+      pkgs = nixpkgs.legacyPackages.${system};
+
+      # Function to create compiler-specific package sets
+      mkPackageSet = compiler: let
+        # Override the stdenv to use the specified compiler
+        stdenv =
+          if compiler == "clang"
+          then pkgs.clangStdenv
+          else pkgs.stdenv;
+
+        mkLib = shared:
+          stdenv.mkDerivation {
+            inherit name src;
+            nativeBuildInputs = with pkgs;
+              [cmake ninja doxygen pkg-config graphviz]
+              ++ (
+                if compiler == "clang"
+                then [pkgs.clang]
+                else [pkgs.gcc]
+              );
+
+            buildInputs = with pkgs; [openssl];
+
+            cmakeFlags = [
+              "-GNinja"
+              "-DOQS_DIST_BUILD=ON"
+              "-DOQS_BUILD_ONLY_LIB=ON"
+              "-DBUILD_SHARED_LIBS=${
+                if shared
+                then "ON"
+                else "OFF"
+              }"
+              "-DCMAKE_INSTALL_LIBDIR=lib"
+              "-DCMAKE_INSTALL_INCLUDEDIR=include"
+              "-DCMAKE_INSTALL_PREFIX=${placeholder "out"}"
+              "-DCMAKE_INSTALL_FULL_LIBDIR=${placeholder "out"}/lib"
+              "-DCMAKE_INSTALL_FULL_INCLUDEDIR=${placeholder "out"}/include"
+            ];
+          };
+      in {
+        shared = mkLib true;
+        static = mkLib false;
+      };
+
+      # Create development shell for specified compiler
+      mkDevShell = compiler: let
+        packageSet = mkPackageSet compiler;
+      in
+        pkgs.mkShell {
+          inherit (packageSet.shared) nativeBuildInputs buildInputs;
+
+          # astyle formats C source code and alejandra formats nix source code
+          packages = with pkgs; [astyle alejandra];
+
+          shellHook = ''
+            export CMAKE_EXPORT_COMPILE_COMMANDS=1
+            echo "Using ${compiler} toolchain"
+          '';
+        };
+    in {
+      packages = {
+        default = (mkPackageSet "gcc").shared; # default is gcc shared
+        gcc = mkPackageSet "gcc";
+        clang = mkPackageSet "clang";
+      };
+
+      # Development shells
+      devShells = {
+        default = mkDevShell "gcc";
+        gcc = mkDevShell "gcc";
+        clang = mkDevShell "clang";
+      };
+    });
+}