anchor.diff: -{ lib, stdenv
  +{ lib
  +, stdenv
   , fetchurl
   , autoPatchelfHook
   , fixDarwinDylibNames
  
positive.code:     ++ optional stdenv.isLinux autoPatchelfHook
      ++ optional stdenv.isDarwin fixDarwinDylibNames;
  
    outputs = [ "out" "dev" "lib"];
  
    unpackCmd = "unzip $curSrc";
  
  
negative.code:   };
  
    # assemble srcs
    srcs = map
      (component:
        (fetcher (srcFilename component arch version rels.${component} or "") hashes.${component} or ""))
      components;
  
    pname = "oracle-instantclient";
    extLib = stdenv.hostPlatform.extensions.sharedLibrary;
  in
  stdenv.mkDerivation {
    inherit pname version srcs;
  
    buildInputs = [ stdenv.cc.cc.lib ]
  