anchor.diff:  
   %-define(TRACE(X,Y), io:format(X,Y)).
   -define(TRACE(X,Y), ok).
  +
  +-define(LOG_CC_FAILS, false).
  +%%-define(LOG_CC_FAILS, true).
  +
   -include("scalaris.hrl").
   -include("client_types.hrl").
   
  
positive.code: wf_set_wl(prbr_bottom, _UI = none, {TxId, -1}) ->
      set_writelock(new_entry(), TxId);
  wf_set_wl(prbr_bottom, _UI = none, {TxId, _}) ->
      ct:pal("should only happen in tester unittests~n"),
      set_writelock(new_entry(), TxId);
  wf_set_wl(DBEntry, _UI = none, {TxId, _Vers}) ->
      set_writelock(DBEntry, TxId).
  
negative.code: cc_commit_write({_WL, Vers}, _WF, _Val = {_TxId, TLogVers, _NewVal}) ->
      Checks =
          [ { Vers =:= TLogVers,  {version_mismatch, TLogVers, Vers} } ],
      cc_return_val(cc_commit_write, Checks, _UI_if_ok = none, ?LOG_CC_FAILS);
  %% in case of fast write we get the value of the last read as write
  %% value, which here was produced by the read filter of set_lock
  cc_commit_write({_RL, _WL, Vers}, _WF, _Val = {_TxId, TLogVers, _NewVal}) ->
      Checks =
          [ { Vers =:= TLogVers,  {version_mismatch, TLogVers, Vers} } ],
      cc_return_val(cc_commit_write, Checks, _UI_if_ok = none, ?LOG_CC_FAILS).
  
  
  -spec wf_val_unset_wl
  