anchor.diff:  { lib, stdenv, fetchurl, ncurses, pkgconfig
  +
  +# `ps` with systemd support is able to properly report different
  +# attributes like unit name, so we want to have it on linux.
  +# The strange `boostrap` condition is here because `procps` can be
  +# pulled in to early in bootstrap process, when `stdenv` is not yet
  +# functional enought to build `systemd` (or its dependencies).
  +# See https://github.com/NixOS/nixpkgs/pull/43817#issuecomment-408346135
  +, withSystemd ? stdenv.isLinux && !(lib.hasPrefix "bootstrap" stdenv.name)
  +, systemd
   
   # procps is mostly Linux-only. Most commands require a running Linux
   # system (or very similar like that found in Cygwin). The one
   # exception is ‘watch’ which is portable enough to run on pretty much
   # any UNIX-compatible system.
  -, watchOnly ? !(stdenv.isLinux || stdenv.isCygwin) }:
  +, watchOnly ? !(stdenv.isLinux || stdenv.isCygwin)
  +}:
   
   stdenv.mkDerivation rec {
     name = "procps-${version}";
  
positive.code:     sha256 = "0r84kwa5fl0sjdashcn4vh7hgfm7ahdcysig3mcjvpmkzi7p9g8h";
    };
  
    buildInputs = [ ncurses ];
    nativeBuildInputs = [ pkgconfig ];
  
    makeFlags = [ "usrbin_execdir=$(out)/bin" ]
  
negative.code: 
    # Too red
    configureFlags = [ "--disable-modern-top" ]
      ++ lib.optional withSystemd "--with-systemd"
      ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform)
      [ "ac_cv_func_malloc_0_nonnull=yes"
        "ac_cv_func_realloc_0_nonnull=yes" ];
  