anchor.diff:  
     src = fetchurl {
       urls = tarballUrls version;
  +    multihash = "QmTUVjSnPLPmYQmDFKb5Twfb3AQxv9Rx7FcLwjoQPfa6My";
       allowHashOutput = false;
  -    multihash = "QmTUVjSnPLPmYQmDFKb5Twfb3AQxv9Rx7FcLwjoQPfa6My";
       sha256 = "3f300087c42b6f35591163b48246b4098ce39c4c6f5d55a83023c903c5776553";
     };
   
  
positive.code: 
    tarballUrls = version: [
      "https://fedorahosted.org/releases/e/l/elfutils/${version}/elfutils-${version}.tar.bz2"
      "mirror://gentoo/elfutils-${version}.tar.bz2"
    ];
  
    version = "0.167";
  
negative.code:   ];
  
    passthru = {
      inherit version;
  
      srcVerification = fetchurl rec {
        failEarly = true;
        urls = tarballUrls "0.167";
  