anchor.diff:    , withLibseccomp ? lib.any (lib.meta.platformMatch stdenv.hostPlatform) libseccomp.meta.platforms, libseccomp
     , withAWS ? stdenv.isLinux || stdenv.isDarwin, aws-sdk-cpp
   
  -  , name, suffix ? "", src, includesPerl ? false, fromGit ? false
  +  , name, suffix ? "", src, includesPerl ? false
   
     }:
     let
  
positive.code:       version = lib.getVersion name;
  
        is20 = lib.versionAtLeast version "2.0pre";
  
        VERSION_SUFFIX = lib.optionalString fromGit suffix;
  
        outputs = [ "out" "dev" "man" "doc" ];
  
        nativeBuildInputs =
          [ pkgconfig ]
          ++ lib.optionals (!is20) [ curl perl ]
          ++ lib.optionals fromGit [ autoreconfHook autoconf-archive bison flex libxml2 libxslt docbook5 docbook_xsl_ns jq ];
  
        buildInputs = [ curl openssl sqlite xz bzip2 nlohmann_json ]
          ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium
          ++ lib.optionals is20 [ brotli boost editline ]
          ++ lib.optional withLibseccomp libseccomp
          ++ lib.optional (withAWS && is20)
              ((aws-sdk-cpp.override {
  
negative.code:   });
  
    nixUnstable = lib.lowPrio (callPackage common rec {
      name = "nix-2.4${suffix}";
      suffix = "pre7250_94c93437";
      src = fetchurl {
        url = "https://hydra.nixos.org/build/112193977/download/3/nix-2.4${suffix}.tar.xz";
        sha256 = "f9baf241c9449c1e3e5c9610adbcd2ce9e5fbcab16aff3ba3030d2fad7b34d7b";
      };
  
      inherit storeDir stateDir confDir boehmgc;
    });
  
    nixFlakes = lib.lowPrio (callPackage common rec {
      name = "nix-2.4${suffix}";
      suffix = "pre20200207_d2032ed";
      src = fetchurl {
        url = "https://hydra.nixos.org/build/111815420/download/3/nix-2.4${suffix}.tar.xz";
        sha256 = "e72a20efeee4ccc704cca3a06de9185fb8742bc7ef1a62af5896ec0f379b9ceb";
      };
  
      inherit storeDir stateDir confDir boehmgc;
    });
  