anchor.diff:    src = fetchurl {
       urls = tarballUrls version;
       hashOutput = false;
  -    sha256 = "7cd8cc2e35b1aaede6084ea57cc9447752f498daaea854100a4bad567614977d";
  +    sha256 = "b8822cb4769e2d759c828c06f196614936c88c141c3132b18252fe25c2b635ce";
     };
   
     buildInputs = [
  
positive.code: }:
  
  let
    version = "1.17";
  
    tarballUrls = version: [
      "mirror://gnu/gdbm/gdbm-${version}.tar.gz"
  
negative.code:   passthru = {
      srcVerification = fetchurl rec {
        failEarly = true;
        urls = tarballUrls "1.18";
        fullOpts = {
          pgpsigUrls = map (n: "${n}.sig") urls;
          pgpKeyFingerprint = "325F 650C 4C2B 6AD5 8807  327A 3602 B07F 55D0 C732";
        };
        inherit (src) outputHashAlgo;
        outputHash = "b8822cb4769e2d759c828c06f196614936c88c141c3132b18252fe25c2b635ce";
      };
    };
  
  