anchor.diff:      zstd
       lapack
       libxml2
  -    llvm_9
  +    _llvm_9
       lz4
       xz
       gsl
  
positive.code: 
    patches = [
      ./sw_vers.patch
  
      # Fix builtin_llvm=OFF support
      (fetchpatch {
        url = "https://github.com/root-project/root/commit/0cddef5d3562a89fe254e0036bb7d5ca8a5d34d2.diff";
        excludes = [ "interpreter/cling/tools/plugins/clad/CMakeLists.txt" ];
        sha256 = "sha256-VxWUbxRHB3O6tERFQdbGI7ypDAZD3sjSi+PYfu1OAbM=";
      })
    ];
  
    # Fix build against vanilla LLVM 9
  
negative.code: , noSplash ? false
  }:
  
  let
  
    _llvm_9 = llvm_9.overrideAttrs (prev: {
      patches = (prev.patches or []) ++ [
        (fetchpatch {
          url = "https://github.com/root-project/root/commit/a9c961cf4613ff1f0ea50f188e4a4b0eb749b17d.diff";
          stripLen = 3;
          hash = "sha256-LH2RipJICEDWOr7JzX5s0QiUhEwXNMFEJihYKy9qWpo=";
        })
      ];
    });
  
  in
  
  stdenv.mkDerivation rec {
    pname = "root";
    version = "6.26.04";
  
    src = fetchurl {
      url = "https://root.cern.ch/download/root_v${version}.source.tar.gz";
      hash = "sha256-onHPgngtbtLIfqXu9mgYA/LmnhezA2352GNjbpNYQh4=";
    };
  
    nativeBuildInputs = [ makeWrapper cmake pkg-config git ];
  