anchor.diff:  
     meta = {
       homepage = http://www.gnu.org/software/libc/;
  -    description = "The GNU C Library"
  -      + stdenv.lib.optionalString (hurdHeaders != null) ", for GNU/Hurd";
  +    description = "The GNU C Library";
   
       longDescription =
         '' Any Unix-like operating system needs a C library: the library which
  
positive.code: 
  // stdenv.lib.optionalAttrs withGd {
    preBuild = "unset NIX_DONT_SET_RPATH";
  }
  
  // stdenv.lib.optionalAttrs (hurdHeaders != null) {
    # Work around the fact that the configure snippet that looks for
    # <hurd/version.h> does not honor `--with-headers=$sysheaders' and that
    # glibc expects Mach, Hurd, and pthread headers to be in the same place.
    CPATH = "${hurdHeaders}/include:${machHeaders}/include:${libpthreadHeaders}/include";
  
    # Install NSS stuff in the right place.
    # XXX: This will be needed for all new glibcs and isn't Hurd-specific.
    makeFlags = ''vardbdir="$out/var/db"'';
  })
  
negative.code: 
    /* Don't try to apply these patches to the Hurd's snapshot, which is
       older.  */
    patches =
      [ /* Have rpcgen(1) look for cpp(1) in $PATH.  */
        ./rpcgen-path.patch
  
  