anchor.diff:  assert stdenv.cc ? libc ;
   assert stdenv.cc.libc != null ;
   
  -stdenv.mkDerivation {
  +stdenv.mkDerivation rec {
     pname = "gcl";
  -  version = "2.6.13pre50";
  +  version = "2.6.13pre124";
   
     src = fetchgit {
  -    sha256 = "0vpxb6z5g9fjavrgx8gz8fsjvskfz64f63qibh5s00fvvndlwi88";
  +    sha256 = "sha256-e4cUQlNSfdz+B3urlZ82pf7fTc6aoloUyDDorAUi5kc=";
       url = "https://git.savannah.gnu.org/r/gcl.git";
  -    rev = "refs/tags/Version_2_6_13pre50";
  +    rev = "refs/tags/Version_${builtins.replaceStrings ["."] ["_"] version}";
     };
   
     postPatch = ''
       sed -e 's/<= obj-date/<= (if (= 0 obj-date) 1 obj-date)/' -i lsp/make.lisp
  -  ''
  -  # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=902475
  -  + ''
  -    substituteInPlace h/elf64_i386_reloc.h \
  -      --replace 'case R_X86_64_PC32:' 'case R_X86_64_PC32: case R_X86_64_PLT32:'
     '';
   
     sourceRoot = "gcl/gcl";
  +
  +  # breaks when compiling in parallel
  +  enableParallelBuilding = false;
   
     patches = [];
   
  
positive.code: { lib, stdenv, fetchgit, mpfr, m4, binutils, emacs, zlib, which
  , texinfo, libX11, xorgproto, libXi, gmp, readline, strace
  , libXext, libXt, libXaw, libXmu } :
  
  assert stdenv ? cc ;
  
negative.code:     mpfr m4 binutils emacs gmp
      libX11 xorgproto libXi
      libXext libXt libXaw libXmu
      zlib which texinfo readline
    ];
  
    configureFlags = [
  