anchor.diff: -{ stdenv, fetchFromGitHub, cmake, boost, libevent, double-conversion, glog
  -, gflags, libiberty, openssl }:
  +{ stdenv
  +, fetchFromGitHub
  +, cmake
  +, boost
  +, libevent
  +, double-conversion
  +, glog
  +, gflags
  +, libiberty
  +, lz4
  +, lzma
  +, zlib
  +, jemalloc
  +, openssl
  +, pkg-config
  +, libunwind
  +, fmt
  +}:
   
  -stdenv.mkDerivation rec {
  +stdenv.mkDerivation (rec {
     pname = "folly";
  -  version = "2019.11.11.00";
  +  version = "2020.09.28.00";
   
     src = fetchFromGitHub {
       owner = "facebook";
       repo = "folly";
       rev = "v${version}";
  -    sha256 = "1sgv7sdalbs7zhz3zcc95gn2h8j2xjf7hkw2c618zc3pdn6aa58w";
  +    sha256 = "1ry2nqfavcbz0jvsqw71105gbxm5hpmdi2k1w155m957jrv3n5vg";
     };
   
  -  nativeBuildInputs = [ cmake ];
  +  nativeBuildInputs = [
  +    cmake
  +    pkg-config
  +  ];
   
     # See CMake/folly-deps.cmake in the Folly source tree.
     buildInputs = [
  
positive.code:     libevent
      libiberty
      openssl
    ];
  
    enableParallelBuilding = true;
  
    meta = with stdenv.lib; {
      description = "An open-source C++ library developed and used at Facebook";
  
negative.code:     platforms = [ "x86_64-linux" "x86_64-darwin" ];
      maintainers = with maintainers; [ abbradar pierreis ];
    };
  } // stdenv.lib.optionalAttrs stdenv.isDarwin {
    LDFLAGS = "-ljemalloc";
  })
  