anchor.diff:  { fetchurl, stdenv, ncurses, readline, gmp, mpfr, expat, texinfo
  -, dejagnu, python, target ? null
  +, dejagnu, python, pkgconfig, guile, target ? null
   
   # Additional dependencies for GNU/Hurd.
   , mig ? null, hurd ? null
  
positive.code: 
  let
  
    basename = "gdb-7.7";
  
    # Whether (cross-)building for GNU/Hurd.  This is an approximation since
    # having `stdenv ? cross' doesn't tell us if we're building `crossDrv' and
  
negative.code:       ("-" + target.config);
  
    src = fetchurl {
      url = "mirror://gnu/gdb/${basename}.tar.xz";
      sha256 = "49c4abe174f79f54e1f9e75210ffb590d9b497d5b5200b5398c0e073a4ecb875";
    };
  
    patches = [ ./edit-signals.patch ];
  