diff --git a/C/absmi.c b/C/absmi.c
index 9218014e4..431781709 100755
--- a/C/absmi.c
+++ b/C/absmi.c
@@ -2948,45 +2948,8 @@ Yap_absmi(int inp)
       if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
 	PredEntry *ap = PREG->u.pp.p;
 
-	if (ap->PredFlags & HiddenPredFlag) {
-	  CACHE_Y_AS_ENV(YREG);
-	  CACHE_A1();
-	  check_depth(DEPTH, ap);
-	  PREG = ap->CodeOfPred;
-	  /* for profiler */
-	  save_pc();
-	  ALWAYS_LOOKAHEAD(ap->OpcodeOfPred);
-	  /* do deallocate */
-	  CPREG = (yamop *) ENV_YREG[E_CP];
-	  ENV_YREG = ENV = (CELL *) ENV_YREG[E_E];
-#ifdef FROZEN_STACKS
-	  { 
-	    choiceptr top_b = PROTECT_FROZEN_B(B);
-
-#ifdef YAPOR_SBA
-	    if (ENV_YREG > (CELL *) top_b || ENV_YREG < H) ENV_YREG = (CELL *) top_b;
-#else
-	    if (ENV_YREG > (CELL *) top_b) ENV_YREG = (CELL *) top_b;
-#endif
-	    else ENV_YREG = (CELL *)((CELL)ENV_YREG + ENV_Size(CPREG));
-	  }
-#else
-	  if (ENV_YREG > (CELL *)B) {
-	    ENV_YREG = (CELL *)B;
-	  } else {
-	    ENV_YREG = (CELL *) ((CELL) ENV_YREG + ENV_Size(CPREG));
-	  }
-#endif /* FROZEN_STACKS */
-	  WRITEBACK_Y_AS_ENV();
-	  /* setup GB */
-	  ENV_YREG[E_CB] = (CELL) B;
-	  ALWAYS_GONext();
-	  ALWAYS_END_PREFETCH();
-	  ENDCACHE_Y_AS_ENV();
-	} else {
-	  SREG = (CELL *) ap;
-	  goto creepde;
-	}
+	SREG = (CELL *) ap;
+	goto creepde;
       }
       /* set SREG for next instructions */
       SREG = (CELL *) PREG->u.p.p;
@@ -6918,7 +6881,7 @@ Yap_absmi(int inp)
 
       BOp(call_cpred, Osbpp);
       check_trail(TR);
-      if (!(PREG->u.Osbpp.p->PredFlags & (SafePredFlag|HiddenPredFlag))) {
+      if (!(PREG->u.Osbpp.p->PredFlags & (SafePredFlag))) {
 	CACHE_Y_AS_ENV(YREG);
 	check_stack(NoStackCall, H);
 	ENDCACHE_Y_AS_ENV();
diff --git a/C/agc.c b/C/agc.c
index ecf7f5108..d5d35e5b1 100644
--- a/C/agc.c
+++ b/C/agc.c
@@ -557,7 +557,7 @@ p_agc_threshold(USES_REGS1)
 void 
 Yap_init_agc(void)
 {
-  Yap_InitCPred("$atom_gc", 0, p_atom_gc, HiddenPredFlag);
-  Yap_InitCPred("$inform_agc", 3, p_inform_agc, HiddenPredFlag);
-  Yap_InitCPred("$agc_threshold", 1, p_agc_threshold, HiddenPredFlag|SafePredFlag);
+  Yap_InitCPred("$atom_gc", 0, p_atom_gc, 0);
+  Yap_InitCPred("$inform_agc", 3, p_inform_agc, 0);
+  Yap_InitCPred("$agc_threshold", 1, p_agc_threshold, SafePredFlag);
 }
diff --git a/C/arrays.c b/C/arrays.c
index 298818265..d87a081cb 100644
--- a/C/arrays.c
+++ b/C/arrays.c
@@ -2445,9 +2445,9 @@ p_static_array_location( USES_REGS1 )
 void 
 Yap_InitArrayPreds( void )
 {
-  Yap_InitCPred("$create_array", 2, p_create_array, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$array_references", 3, p_array_references, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$array_arg", 3, p_array_arg, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$create_array", 2, p_create_array, SyncPredFlag);
+  Yap_InitCPred("$array_references", 3, p_array_references, SafePredFlag);
+  Yap_InitCPred("$array_arg", 3, p_array_arg, SafePredFlag);
   Yap_InitCPred("static_array", 3, p_create_static_array, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("resize_static_array", 3, p_resize_static_array, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("mmapped_array", 4, p_create_mmapped_array, SafePredFlag|SyncPredFlag);
@@ -2457,10 +2457,10 @@ Yap_InitArrayPreds( void )
   Yap_InitCPred("array_element", 3, p_access_array, 0);
   Yap_InitCPred("reset_static_array", 1, p_clear_static_array, SafePredFlag);
   Yap_InitCPred("close_static_array", 1, p_close_static_array, SafePredFlag);
-  Yap_InitCPred("$sync_mmapped_arrays", 0, p_sync_mmapped_arrays, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$compile_array_refs", 0, p_compile_array_refs, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$array_refs_compiled", 0, p_array_refs_compiled, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$static_array_properties", 3, p_static_array_properties, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$sync_mmapped_arrays", 0, p_sync_mmapped_arrays, SafePredFlag);
+  Yap_InitCPred("$compile_array_refs", 0, p_compile_array_refs, SafePredFlag);
+  Yap_InitCPred("$array_refs_compiled", 0, p_array_refs_compiled, SafePredFlag);
+  Yap_InitCPred("$static_array_properties", 3, p_static_array_properties, SafePredFlag);
   Yap_InitCPred("static_array_to_term", 2, p_static_array_to_term, 0L);
   Yap_InitCPred("static_array_location", 2, p_static_array_location, 0L);
 }
diff --git a/C/attvar.c b/C/attvar.c
index 454b1b2f9..0c6fcf9ad 100644
--- a/C/attvar.c
+++ b/C/attvar.c
@@ -1075,7 +1075,7 @@ void Yap_InitAttVarPreds(void)
   Yap_InitCPred("all_attvars", 1, p_all_attvars, 0);
   CurrentModule = OldCurrentModule;
   Yap_InitCPred("attvar", 1, p_is_attvar, SafePredFlag|TestPredFlag);
-  Yap_InitCPred("$att_bound", 1, p_attvar_bound, SafePredFlag|TestPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$att_bound", 1, p_attvar_bound, SafePredFlag|TestPredFlag);
 }
 
 
diff --git a/C/bb.c b/C/bb.c
index a42034fba..2b5cf8402 100644
--- a/C/bb.c
+++ b/C/bb.c
@@ -375,6 +375,6 @@ Yap_InitBBPreds(void)
   Yap_InitCPred("bb_get", 2, p_bb_get, 0);
   Yap_InitCPred("bb_delete", 2, p_bb_delete, 0);
   Yap_InitCPred("bb_update", 3, p_bb_update, 0);
-  Yap_InitCPred("$resize_bb_int_keys", 1, p_resize_bb_int_keys, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$resize_bb_int_keys", 1, p_resize_bb_int_keys, SafePredFlag|SyncPredFlag);
 }
 
diff --git a/C/bignum.c b/C/bignum.c
index b6997ec53..b3da97128 100644
--- a/C/bignum.c
+++ b/C/bignum.c
@@ -556,8 +556,8 @@ Yap_BlobStringOfTermAndLength(Term t, size_t *sp)
 void
 Yap_InitBigNums(void)
 {
-  Yap_InitCPred("$has_bignums", 0, p_has_bignums, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$bignum", 1, p_is_bignum, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$has_bignums", 0, p_has_bignums, SafePredFlag);
+  Yap_InitCPred("$bignum", 1, p_is_bignum, SafePredFlag);
   Yap_InitCPred("rational", 3, p_rational, 0);
   Yap_InitCPred("rational", 1, p_is_rational, SafePredFlag);
 }
diff --git a/C/cdmgr.c b/C/cdmgr.c
index 78b0827a5..b6d0b6afe 100644
--- a/C/cdmgr.c
+++ b/C/cdmgr.c
@@ -4335,6 +4335,42 @@ p_all_system_pred( USES_REGS1 )
 	 pe->OpcodeOfPred == Yap_opcode(_try_userc));
 }
 
+void
+Yap_HidePred(PredEntry *pe)
+{
+  Prop p0 = AbsPredProp(pe);
+  if (pe->ArityOfPE == 0) {
+    Atom a = (Atom)pe->FunctorOfPred;
+
+    p0 = RepAtom(a)->PropsOfAE;
+    if (p0 == AbsPredProp(pe)) {
+      RepAtom(a)->PropsOfAE = pe->NextOfPE;
+    } else {
+      while (p0->NextOfPE != AbsPredProp(pe))
+	p0 = p0->NextOfPE;
+      if (p0 == NIL)
+	return;
+      p0->NextOfPE = pe->NextOfPE;
+    }
+  } else {
+    Functor         funt = pe->FunctorOfPred;
+
+    p0 = funt->PropsOfFE;
+    if (p0 == AbsPredProp(pe)) {
+      funt->PropsOfFE = pe->NextOfPE;
+    } else {
+      while (p0->NextOfPE != AbsPredProp(pe))
+	p0 = p0->NextOfPE;
+      if (p0 == NIL)
+	return;
+      p0->NextOfPE = pe->NextOfPE;
+    }
+  }
+  pe->NextOfPE = HIDDEN_PREDICATES;
+  HIDDEN_PREDICATES = AbsPredProp(pe);
+  pe->PredFlags |= HiddenPredFlag;  
+}
+
 static Int			/* $system_predicate(P) */
 p_hide_predicate( USES_REGS1 )
 {
@@ -4342,12 +4378,15 @@ p_hide_predicate( USES_REGS1 )
 
   Term t1 = Deref(ARG1);
   Term mod = Deref(ARG2);
+  Prop p0;
 
  restart_system_pred:
   if (IsVarTerm(t1))
     return (FALSE);
   if (IsAtomTerm(t1)) {
-    pe = RepPredProp(Yap_GetPredPropByAtom(AtomOfTerm(t1), mod));
+    Atom a = AtomOfTerm(t1);
+
+    pe = RepPredProp(Yap_GetPredPropByAtom(a, mod));
   } else if (IsApplTerm(t1)) {
     Functor         funt = FunctorOfTerm(t1);
     if (IsExtensionFunctor(funt)) {
@@ -4368,15 +4407,16 @@ p_hide_predicate( USES_REGS1 )
     }
     pe = RepPredProp(Yap_GetPredPropByFunc(funt, mod));
   } else if (IsPairTerm(t1)) {
-    return (TRUE);
+    return TRUE;
   } else
-    return (FALSE);
+    return FALSE;
   if (EndOfPAEntr(pe))
     return FALSE;
-  pe->PredFlags |= HiddenPredFlag;
-  return(TRUE);
+  Yap_HidePred(pe);
+  return TRUE;
 }
 
+
 static Int			/* $hidden_predicate(P) */
 p_hidden_predicate( USES_REGS1 )
 {
@@ -5888,65 +5928,65 @@ Yap_InitCdMgr(void)
   CACHE_REGS
   Term cm = CurrentModule;
 
-  Yap_InitCPred("$compile_mode", 2, p_compile_mode, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$start_consult", 3, p_startconsult, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$show_consult_level", 1, p_showconslultlev, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$end_consult", 0, p_endconsult, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$set_spy", 2, p_setspy, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$rm_spy", 2, p_rmspy, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$compile_mode", 2, p_compile_mode, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$start_consult", 3, p_startconsult, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$show_consult_level", 1, p_showconslultlev, SafePredFlag);
+  Yap_InitCPred("$end_consult", 0, p_endconsult, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$set_spy", 2, p_setspy, SyncPredFlag);
+  Yap_InitCPred("$rm_spy", 2, p_rmspy, SafePredFlag|SyncPredFlag);
   /* gc() may happen during compilation, hence these predicates are
 	now unsafe */
-  Yap_InitCPred("$compile", 4, p_compile, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$compile_dynamic", 5, p_compile_dynamic, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$purge_clauses", 2, p_purge_clauses, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$in_use", 2, p_in_use, TestPredFlag | SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$is_dynamic", 2, p_is_dynamic, TestPredFlag | SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$is_metapredicate", 2, p_is_metapredicate, TestPredFlag | SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$is_expand_goal_or_meta_predicate", 2, p_is_expandgoalormetapredicate, TestPredFlag | SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$is_log_updatable", 2, p_is_log_updatable, TestPredFlag | SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$is_source", 2, p_is_source, TestPredFlag | SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$owner_file", 3, p_owner_file, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$mk_d", 2, p_mk_d, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$pred_exists", 2, p_pred_exists, TestPredFlag | SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$number_of_clauses", 3, p_number_of_clauses, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$undefined", 2, p_undefined, SafePredFlag|TestPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$optimizer_on", 0, p_optimizer_on, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$clean_up_dead_clauses", 0, p_clean_up_dead_clauses, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$optimizer_off", 0, p_optimizer_off, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$kill_dynamic", 2, p_kill_dynamic, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$new_multifile", 3, p_new_multifile, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$is_multifile", 2, p_is_multifile, TestPredFlag | SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$is_profiled", 1, p_is_profiled, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$profile_info", 3, p_profile_info, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$profile_reset", 2, p_profile_reset, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$is_call_counted", 1, p_is_call_counted, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$call_count_info", 3, p_call_count_info, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$call_count_set", 6, p_call_count_set, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$call_count_reset", 0, p_call_count_reset, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$toggle_static_predicates_in_use", 0, p_toggle_static_predicates_in_use, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$set_pred_module", 2, p_set_pred_module, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$parent_pred", 3, p_parent_pred, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$system_predicate", 2, p_system_pred, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$all_system_predicate", 3, p_all_system_pred, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$hide_predicate", 2, p_hide_predicate, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$hidden_predicate", 2, p_hidden_predicate, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$pred_for_code", 5, p_pred_for_code, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$current_stack", 1, p_current_stack, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$log_update_clause", 4, p_log_update_clause, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$continue_log_update_clause", 5, p_continue_log_update_clause, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$log_update_clause_erase", 4, p_log_update_clause_erase, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$continue_log_update_clause_erase", 5, p_continue_log_update_clause_erase, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$static_clause", 4, p_static_clause, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$continue_static_clause", 5, p_continue_static_clause, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$static_pred_statistics", 5, p_static_pred_statistics, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$p_nth_clause", 4, p_nth_clause, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$program_continuation", 3, p_program_continuation, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$compile", 4, p_compile, SyncPredFlag);
+  Yap_InitCPred("$compile_dynamic", 5, p_compile_dynamic, SyncPredFlag);
+  Yap_InitCPred("$purge_clauses", 2, p_purge_clauses, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$in_use", 2, p_in_use, TestPredFlag | SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$is_dynamic", 2, p_is_dynamic, TestPredFlag | SafePredFlag);
+  Yap_InitCPred("$is_metapredicate", 2, p_is_metapredicate, TestPredFlag | SafePredFlag);
+  Yap_InitCPred("$is_expand_goal_or_meta_predicate", 2, p_is_expandgoalormetapredicate, TestPredFlag | SafePredFlag);
+  Yap_InitCPred("$is_log_updatable", 2, p_is_log_updatable, TestPredFlag | SafePredFlag);
+  Yap_InitCPred("$is_source", 2, p_is_source, TestPredFlag | SafePredFlag);
+  Yap_InitCPred("$owner_file", 3, p_owner_file, SafePredFlag);
+  Yap_InitCPred("$mk_d", 2, p_mk_d, SafePredFlag);
+  Yap_InitCPred("$pred_exists", 2, p_pred_exists, TestPredFlag | SafePredFlag);
+  Yap_InitCPred("$number_of_clauses", 3, p_number_of_clauses, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$undefined", 2, p_undefined, SafePredFlag|TestPredFlag);
+  Yap_InitCPred("$optimizer_on", 0, p_optimizer_on, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$clean_up_dead_clauses", 0, p_clean_up_dead_clauses, SyncPredFlag);
+  Yap_InitCPred("$optimizer_off", 0, p_optimizer_off, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$kill_dynamic", 2, p_kill_dynamic, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$new_multifile", 3, p_new_multifile, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$is_multifile", 2, p_is_multifile, TestPredFlag | SafePredFlag);
+  Yap_InitCPred("$is_profiled", 1, p_is_profiled, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$profile_info", 3, p_profile_info, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$profile_reset", 2, p_profile_reset, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$is_call_counted", 1, p_is_call_counted, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$call_count_info", 3, p_call_count_info, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$call_count_set", 6, p_call_count_set, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$call_count_reset", 0, p_call_count_reset, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$toggle_static_predicates_in_use", 0, p_toggle_static_predicates_in_use, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$set_pred_module", 2, p_set_pred_module, SafePredFlag);
+  Yap_InitCPred("$parent_pred", 3, p_parent_pred, SafePredFlag);
+  Yap_InitCPred("$system_predicate", 2, p_system_pred, SafePredFlag);
+  Yap_InitCPred("$all_system_predicate", 3, p_all_system_pred, SafePredFlag);
+  Yap_InitCPred("$hide_predicate", 2, p_hide_predicate, SafePredFlag);
+  Yap_InitCPred("$hidden_predicate", 2, p_hidden_predicate, SafePredFlag);
+  Yap_InitCPred("$pred_for_code", 5, p_pred_for_code, SyncPredFlag);
+  Yap_InitCPred("$current_stack", 1, p_current_stack, SyncPredFlag);
+  Yap_InitCPred("$log_update_clause", 4, p_log_update_clause, SyncPredFlag);
+  Yap_InitCPred("$continue_log_update_clause", 5, p_continue_log_update_clause, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$log_update_clause_erase", 4, p_log_update_clause_erase, SyncPredFlag);
+  Yap_InitCPred("$continue_log_update_clause_erase", 5, p_continue_log_update_clause_erase, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$static_clause", 4, p_static_clause, SyncPredFlag);
+  Yap_InitCPred("$continue_static_clause", 5, p_continue_static_clause, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$static_pred_statistics", 5, p_static_pred_statistics, SyncPredFlag);
+  Yap_InitCPred("$p_nth_clause", 4, p_nth_clause, SyncPredFlag);
+  Yap_InitCPred("$program_continuation", 3, p_program_continuation, SafePredFlag|SyncPredFlag);
   CurrentModule = HACKS_MODULE;
-  Yap_InitCPred("current_choicepoints", 1, p_all_choicepoints, HiddenPredFlag);
-  Yap_InitCPred("current_continuations", 1, p_all_envs, HiddenPredFlag);
-  Yap_InitCPred("choicepoint", 7, p_choicepoint_info, HiddenPredFlag);
-  Yap_InitCPred("continuation", 4, p_env_info, HiddenPredFlag);
-  Yap_InitCPred("cp_to_predicate", 5, p_cpc_info, HiddenPredFlag);
+  Yap_InitCPred("current_choicepoints", 1, p_all_choicepoints, 0);
+  Yap_InitCPred("current_continuations", 1, p_all_envs, 0);
+  Yap_InitCPred("choicepoint", 7, p_choicepoint_info, 0);
+  Yap_InitCPred("continuation", 4, p_env_info,0);
+  Yap_InitCPred("cp_to_predicate", 5, p_cpc_info, 0);
   CurrentModule = cm;
   CurrentModule = DBLOAD_MODULE;
   Yap_InitCPred("dbload_get_space", 4, p_dbload_get_space, 0L);
diff --git a/C/cmppreds.c b/C/cmppreds.c
index d750fe84c..4b833a0e0 100644
--- a/C/cmppreds.c
+++ b/C/cmppreds.c
@@ -728,7 +728,7 @@ Yap_InitCmpPreds(void)
   Yap_InitCmpPred("=<", 2, a_le, SafePredFlag | BinaryPredFlag);
   Yap_InitCmpPred("<", 2, a_lt, SafePredFlag | BinaryPredFlag);
   Yap_InitCmpPred(">=", 2, a_ge, SafePredFlag | BinaryPredFlag);
-  Yap_InitCPred("$a_compare", 3, p_acomp, TestPredFlag | SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$a_compare", 3, p_acomp, TestPredFlag | SafePredFlag);
   Yap_InitCmpPred("\\==", 2, a_noteq, BinaryPredFlag | SafePredFlag);
   Yap_InitCmpPred("@<", 2, a_gen_lt, BinaryPredFlag | SafePredFlag);
   Yap_InitCmpPred("@=<", 2, a_gen_le, BinaryPredFlag | SafePredFlag);
diff --git a/C/corout.c b/C/corout.c
index 7210058d2..9cbf3b3b2 100644
--- a/C/corout.c
+++ b/C/corout.c
@@ -563,12 +563,12 @@ Yap_InitCoroutPreds( void )
   WakeUpCode = pred;
 #endif
   Yap_InitAttVarPreds();
-  Yap_InitCPred("$yap_has_rational_trees", 0, p_yap_has_rational_trees, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$yap_has_coroutining", 0, p_yap_has_coroutining, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$can_unify", 3, p_can_unify, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$non_ground", 2, p_non_ground, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$coroutining", 0, p_coroutining, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$awoken_goals", 1, p_awoken_goals, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$yap_has_rational_trees", 0, p_yap_has_rational_trees, SafePredFlag);
+  Yap_InitCPred("$yap_has_coroutining", 0, p_yap_has_coroutining, SafePredFlag);
+  Yap_InitCPred("$can_unify", 3, p_can_unify, SafePredFlag);
+  Yap_InitCPred("$non_ground", 2, p_non_ground, SafePredFlag);
+  Yap_InitCPred("$coroutining", 0, p_coroutining, SafePredFlag);
+  Yap_InitCPred("$awoken_goals", 1, p_awoken_goals, SafePredFlag);
 }
 
 
diff --git a/C/dbase.c b/C/dbase.c
index 565334911..90fc7cb4d 100644
--- a/C/dbase.c
+++ b/C/dbase.c
@@ -5522,56 +5522,56 @@ Yap_InitDBPreds(void)
   Yap_InitCPred("recorded", 3, p_recorded, SyncPredFlag);
   Yap_InitCPred("recorda", 3, p_rcda, SyncPredFlag);
   Yap_InitCPred("recordz", 3, p_rcdz, SyncPredFlag);
-  Yap_InitCPred("$still_variant", 2, p_still_variant, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$still_variant", 2, p_still_variant, SyncPredFlag);
   Yap_InitCPred("recorda_at", 3, p_rcda_at, SyncPredFlag);
   Yap_InitCPred("recordz_at", 3, p_rcdz_at, SyncPredFlag);
-  Yap_InitCPred("$recordap", 3, p_rcdap, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$recordzp", 3, p_rcdzp, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$recordap", 4, p_drcdap, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$recordzp", 4, p_drcdzp, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$recordap", 3, p_rcdap, SyncPredFlag);
+  Yap_InitCPred("$recordzp", 3, p_rcdzp, SyncPredFlag);
+  Yap_InitCPred("$recordap", 4, p_drcdap, SyncPredFlag);
+  Yap_InitCPred("$recordzp", 4, p_drcdzp, SyncPredFlag);
   Yap_InitCPred("erase", 1, p_erase, SafePredFlag|SyncPredFlag);
-  Yap_InitCPred("$erase_clause", 2, p_erase_clause, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$erase_clause", 2, p_erase_clause, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("increase_reference_count", 1, p_increase_reference_counter, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("decrease_reference_count", 1, p_decrease_reference_counter, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("current_reference_count", 2, p_current_reference_counter, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("erased", 1, p_erased, TestPredFlag | SafePredFlag|SyncPredFlag);
   Yap_InitCPred("instance", 2, p_instance, SyncPredFlag);
-  Yap_InitCPred("$instance_module", 2, p_instance_module, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$instance_module", 2, p_instance_module, SyncPredFlag);
   Yap_InitCPred("eraseall", 1, p_eraseall, SafePredFlag|SyncPredFlag);
-  Yap_InitCPred("$record_stat_source", 4, p_rcdstatp, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$some_recordedp", 1, p_somercdedp, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$first_instance", 3, p_first_instance, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$init_db_queue", 1, p_init_queue, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$db_key", 2, p_db_key, HiddenPredFlag);
-  Yap_InitCPred("$db_enqueue", 2, p_enqueue, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$db_enqueue_unlocked", 2, p_enqueue_unlocked, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$db_dequeue", 2, p_dequeue, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$db_dequeue_unlocked", 2, p_dequeue_unlocked, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$db_peek_queue", 2, p_peek_queue, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$db_clean_queues", 1, p_clean_queues, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$switch_log_upd", 1, p_slu, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$log_upd", 1, p_lu, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$hold_index", 3, p_hold_index, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$fetch_reference_from_index", 3, p_fetch_reference_from_index, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$resize_int_keys", 1, p_resize_int_keys, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$record_stat_source", 4, p_rcdstatp, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$some_recordedp", 1, p_somercdedp, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$first_instance", 3, p_first_instance, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$init_db_queue", 1, p_init_queue, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$db_key", 2, p_db_key, 0L);
+  Yap_InitCPred("$db_enqueue", 2, p_enqueue, SyncPredFlag);
+  Yap_InitCPred("$db_enqueue_unlocked", 2, p_enqueue_unlocked, SyncPredFlag);
+  Yap_InitCPred("$db_dequeue", 2, p_dequeue, SyncPredFlag);
+  Yap_InitCPred("$db_dequeue_unlocked", 2, p_dequeue_unlocked, SyncPredFlag);
+  Yap_InitCPred("$db_peek_queue", 2, p_peek_queue, SyncPredFlag);
+  Yap_InitCPred("$db_clean_queues", 1, p_clean_queues, SyncPredFlag);
+  Yap_InitCPred("$switch_log_upd", 1, p_slu, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$log_upd", 1, p_lu, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$hold_index", 3, p_hold_index, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$fetch_reference_from_index", 3, p_fetch_reference_from_index, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$resize_int_keys", 1, p_resize_int_keys, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("key_statistics", 4, p_key_statistics, SyncPredFlag);
   Yap_InitCPred("$lu_statistics", 5, p_lu_statistics, SyncPredFlag);
   Yap_InitCPred("total_erased", 4, p_total_erased, SyncPredFlag);
   Yap_InitCPred("key_erased_statistics", 5, p_key_erased_statistics, SyncPredFlag);
   Yap_InitCPred("heap_space_info", 3, p_heap_space_info, SyncPredFlag);
   Yap_InitCPred("$nth_instance", 3, p_nth_instance, SyncPredFlag);
-  Yap_InitCPred("$nth_instancep", 3, p_nth_instancep, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$jump_to_next_dynamic_clause", 0, p_jump_to_next_dynamic_clause, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$install_thread_local", 2, p_install_thread_local, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$nth_instancep", 3, p_nth_instancep, SyncPredFlag);
+  Yap_InitCPred("$jump_to_next_dynamic_clause", 0, p_jump_to_next_dynamic_clause, SyncPredFlag);
+  Yap_InitCPred("$install_thread_local", 2, p_install_thread_local, SafePredFlag);
 }
 
 void 
 Yap_InitBackDB(void)
 {
-  Yap_InitCPredBack("$recorded_with_key", 3, 3, in_rded_with_key, co_rded, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPredBack("$recorded_with_key", 3, 3, in_rded_with_key, co_rded, SyncPredFlag);
   RETRY_C_RECORDED_K_CODE = NEXTOP(PredRecordedWithKey->cs.p_code.FirstClause,OtapFs);
-  Yap_InitCPredBack("$recordedp", 3, 3, in_rdedp, co_rdedp, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPredBack("$recordedp", 3, 3, in_rdedp, co_rdedp, SyncPredFlag);
   RETRY_C_RECORDEDP_CODE = NEXTOP(RepPredProp(PredPropByFunc(Yap_MkFunctor(AtomRecordedP, 3),0))->cs.p_code.FirstClause,OtapFs);
   Yap_InitCPredBack("$current_immediate_key", 2, 4, init_current_key, cont_current_key,
-		SyncPredFlag|HiddenPredFlag);
+		SyncPredFlag);
 }
diff --git a/C/depth_bound.c b/C/depth_bound.c
index 20d1abcd9..cf56a392a 100644
--- a/C/depth_bound.c
+++ b/C/depth_bound.c
@@ -72,8 +72,8 @@ static Int p_set_depth_limit_for_next_call( USES_REGS1 )
 void Yap_InitItDeepenPreds(void)
 {
   Yap_InitCPred("get_depth_limit", 1, p_get_depth_limit, SafePredFlag);
-  Yap_InitCPred("$set_depth_limit", 1, p_set_depth_limit, HiddenPredFlag);
-  Yap_InitCPred("$set_depth_limit_for_next_call", 1, p_set_depth_limit_for_next_call, HiddenPredFlag);
+  Yap_InitCPred("$set_depth_limit", 1, p_set_depth_limit, 0);
+  Yap_InitCPred("$set_depth_limit_for_next_call", 1, p_set_depth_limit_for_next_call, 0);
 }
 
 #endif
diff --git a/C/exec.c b/C/exec.c
index 5142f7456..55558eb91 100644
--- a/C/exec.c
+++ b/C/exec.c
@@ -236,7 +236,7 @@ do_execute(Term t, Term mod USES_REGS)
 
     if (a == AtomTrue || a == AtomOtherwise || a == AtomCut)
       return(TRUE);
-    else if (a == AtomFail || a == AtomFalse)
+    else if (a == AtomFail || (a == AtomFalse && !RepPredProp(PredPropByAtom(a, mod))->ModuleOfPred) )
       return(FALSE);
     /* call may not define new system predicates!! */
     pe = RepPredProp(PredPropByAtom(a, mod));
@@ -1789,56 +1789,56 @@ Yap_InitExecFs(void)
   CACHE_REGS
   Term cm = CurrentModule;
   Yap_InitComma();
-  Yap_InitCPred("$execute", 1, p_execute, HiddenPredFlag);
-  Yap_InitCPred("$execute", 2, p_execute2, HiddenPredFlag);
-  Yap_InitCPred("$execute", 3, p_execute3, HiddenPredFlag);
-  Yap_InitCPred("$execute", 4, p_execute4, HiddenPredFlag);
-  Yap_InitCPred("$execute", 5, p_execute5, HiddenPredFlag);
-  Yap_InitCPred("$execute", 6, p_execute6, HiddenPredFlag);
-  Yap_InitCPred("$execute", 7, p_execute7, HiddenPredFlag);
-  Yap_InitCPred("$execute", 8, p_execute8, HiddenPredFlag);
-  Yap_InitCPred("$execute", 9, p_execute9, HiddenPredFlag);
-  Yap_InitCPred("$execute", 10, p_execute10, HiddenPredFlag);
-  Yap_InitCPred("$execute", 11, p_execute11, HiddenPredFlag);
-  Yap_InitCPred("$execute", 12, p_execute12, HiddenPredFlag);
-  Yap_InitCPred("$execute_in_mod", 2, p_execute_in_mod, HiddenPredFlag);
-  Yap_InitCPred("$execute_wo_mod", 2, p_execute_in_mod, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 1, p_execute_0, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 2, p_execute_1, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 3, p_execute_2, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 4, p_execute_3, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 5, p_execute_4, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 6, p_execute_5, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 7, p_execute_6, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 8, p_execute_7, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 9, p_execute_8, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 10, p_execute_9, HiddenPredFlag);
-  Yap_InitCPred("call_with_args", 11, p_execute_10, HiddenPredFlag);
-  Yap_InitCPred("$debug_on", 1, p_debug_on, HiddenPredFlag);
+  Yap_InitCPred("$execute", 1, p_execute, 0);
+  Yap_InitCPred("$execute", 2, p_execute2, 0);
+  Yap_InitCPred("$execute", 3, p_execute3, 0);
+  Yap_InitCPred("$execute", 4, p_execute4, 0);
+  Yap_InitCPred("$execute", 5, p_execute5, 0);
+  Yap_InitCPred("$execute", 6, p_execute6, 0);
+  Yap_InitCPred("$execute", 7, p_execute7, 0);
+  Yap_InitCPred("$execute", 8, p_execute8, 0);
+  Yap_InitCPred("$execute", 9, p_execute9, 0);
+  Yap_InitCPred("$execute", 10, p_execute10, 0);
+  Yap_InitCPred("$execute", 11, p_execute11, 0);
+  Yap_InitCPred("$execute", 12, p_execute12, 0);
+  Yap_InitCPred("$execute_in_mod", 2, p_execute_in_mod, 0);
+  Yap_InitCPred("$execute_wo_mod", 2, p_execute_in_mod, 0);
+  Yap_InitCPred("call_with_args", 1, p_execute_0, 0);
+  Yap_InitCPred("call_with_args", 2, p_execute_1, 0);
+  Yap_InitCPred("call_with_args", 3, p_execute_2, 0);
+  Yap_InitCPred("call_with_args", 4, p_execute_3, 0);
+  Yap_InitCPred("call_with_args", 5, p_execute_4, 0);
+  Yap_InitCPred("call_with_args", 6, p_execute_5, 0);
+  Yap_InitCPred("call_with_args", 7, p_execute_6, 0);
+  Yap_InitCPred("call_with_args", 8, p_execute_7, 0);
+  Yap_InitCPred("call_with_args", 9, p_execute_8, 0);
+  Yap_InitCPred("call_with_args", 10, p_execute_9, 0);
+  Yap_InitCPred("call_with_args", 11, p_execute_10, 0);
+  Yap_InitCPred("$debug_on", 1, p_debug_on, 0);
 #ifdef DEPTH_LIMIT
-  Yap_InitCPred("$execute_under_depth_limit", 2, p_execute_depth_limit, HiddenPredFlag);
+  Yap_InitCPred("$execute_under_depth_limit", 2, p_execute_depth_limit, 0);
 #endif
-  Yap_InitCPred("$execute0", 2, p_execute0, HiddenPredFlag);
-  Yap_InitCPred("$execute_nonstop", 2, p_execute_nonstop, HiddenPredFlag);
-  Yap_InitCPred("$execute_clause", 4, p_execute_clause, HiddenPredFlag);
+  Yap_InitCPred("$execute0", 2, p_execute0, 0);
+  Yap_InitCPred("$execute_nonstop", 2, p_execute_nonstop, 0);
+  Yap_InitCPred("$execute_clause", 4, p_execute_clause, 0);
   CurrentModule = HACKS_MODULE;
-  Yap_InitCPred("current_choice_point", 1, p_save_cp, HiddenPredFlag);
-  Yap_InitCPred("current_choicepoint", 1, p_save_cp, HiddenPredFlag);
-  Yap_InitCPred("env_choice_point", 1, p_save_env_b, HiddenPredFlag);
-  Yap_InitCPred("trail_suspension_marker", 1, p_trail_suspension_marker, HiddenPredFlag);
+  Yap_InitCPred("current_choice_point", 1, p_save_cp, 0);
+  Yap_InitCPred("current_choicepoint", 1, p_save_cp, 0);
+  Yap_InitCPred("env_choice_point", 1, p_save_env_b, 0);
+  Yap_InitCPred("trail_suspension_marker", 1, p_trail_suspension_marker, 0);
   Yap_InitCPred("cut_at", 1, p_clean_ifcp, SafePredFlag);
   CurrentModule = cm;
-  Yap_InitCPred("$pred_goal_expansion_on", 0, p_pred_goal_expansion_on, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$restore_regs", 1, p_restore_regs, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$restore_regs", 2, p_restore_regs2, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$clean_ifcp", 1, p_clean_ifcp, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$pred_goal_expansion_on", 0, p_pred_goal_expansion_on, SafePredFlag);
+  Yap_InitCPred("$restore_regs", 1, p_restore_regs, SafePredFlag);
+  Yap_InitCPred("$restore_regs", 2, p_restore_regs2, SafePredFlag);
+  Yap_InitCPred("$clean_ifcp", 1, p_clean_ifcp, SafePredFlag);
   Yap_InitCPred("qpack_clean_up_to_disjunction", 0, p_cut_up_to_next_disjunction, SafePredFlag);
-  Yap_InitCPred("$jump_env_and_store_ball", 1, p_jump_env, HiddenPredFlag);
-  Yap_InitCPred("$creep_allowed", 0, p_creep_allowed, HiddenPredFlag);
-  Yap_InitCPred("$generate_pred_info", 4, p_generate_pred_info, HiddenPredFlag);
-  Yap_InitCPred("$uncaught_throw", 0, p_uncaught_throw, HiddenPredFlag);
-  Yap_InitCPred("$reset_exception", 1, p_reset_exception, HiddenPredFlag);
-  Yap_InitCPred("$get_exception", 1, p_get_exception, HiddenPredFlag);
+  Yap_InitCPred("$jump_env_and_store_ball", 1, p_jump_env, 0);
+  Yap_InitCPred("$creep_allowed", 0, p_creep_allowed, 0);
+  Yap_InitCPred("$generate_pred_info", 4, p_generate_pred_info, 0);
+  Yap_InitCPred("$uncaught_throw", 0, p_uncaught_throw, 0);
+  Yap_InitCPred("$reset_exception", 1, p_reset_exception, 0);
+  Yap_InitCPred("$get_exception", 1, p_get_exception, 0);
 }
 
 
diff --git a/C/grow.c b/C/grow.c
index f6c9ef817..76c470b8e 100644
--- a/C/grow.c
+++ b/C/grow.c
@@ -1980,11 +1980,11 @@ Yap_total_stack_shift_time(void)
 void
 Yap_InitGrowPreds(void)
 {
-  Yap_InitCPred("$grow_heap", 1, p_growheap, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$grow_stack", 1, p_growstack, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$inform_trail_overflows", 2, p_inform_trail_overflows, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$inform_heap_overflows", 2, p_inform_heap_overflows, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$inform_stack_overflows", 2, p_inform_stack_overflows, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$grow_heap", 1, p_growheap, SafePredFlag);
+  Yap_InitCPred("$grow_stack", 1, p_growstack, SafePredFlag);
+  Yap_InitCPred("$inform_trail_overflows", 2, p_inform_trail_overflows, SafePredFlag);
+  Yap_InitCPred("$inform_heap_overflows", 2, p_inform_heap_overflows, SafePredFlag);
+  Yap_InitCPred("$inform_stack_overflows", 2, p_inform_stack_overflows, SafePredFlag);
   Yap_init_gc();
   Yap_init_agc();
 }
diff --git a/C/heapgc.c b/C/heapgc.c
index aa0598bfe..2f4617664 100644
--- a/C/heapgc.c
+++ b/C/heapgc.c
@@ -4201,8 +4201,8 @@ p_gc( USES_REGS1 )
 void 
 Yap_init_gc(void)
 {
-  Yap_InitCPred("$gc", 0, p_gc, HiddenPredFlag);
-  Yap_InitCPred("$inform_gc", 3, p_inform_gc, HiddenPredFlag);
+  Yap_InitCPred("$gc", 0, p_gc, 0);
+  Yap_InitCPred("$inform_gc", 3, p_inform_gc, 0);
 }
 
 void
diff --git a/C/iopreds.c b/C/iopreds.c
index c2546b803..65d2fafc3 100644
--- a/C/iopreds.c
+++ b/C/iopreds.c
@@ -1114,24 +1114,24 @@ Yap_InitIOPreds(void)
   if (!Stream)
     Stream = (StreamDesc *)Yap_AllocCodeSpace(sizeof(StreamDesc)*MaxStreams);
   /* here the Input/Output predicates */
-  Yap_InitCPred ("$set_read_error_handler", 1, p_set_read_error_handler, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$get_read_error_handler", 1, p_get_read_error_handler, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$read", 7, p_read, SyncPredFlag|HiddenPredFlag|UserCPredFlag);
-  Yap_InitCPred ("$read", 8, p_read2, SyncPredFlag|HiddenPredFlag|UserCPredFlag);
+  Yap_InitCPred ("$set_read_error_handler", 1, p_set_read_error_handler, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$get_read_error_handler", 1, p_get_read_error_handler, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$read", 7, p_read, SyncPredFlag|UserCPredFlag);
+  Yap_InitCPred ("$read", 8, p_read2, SyncPredFlag|UserCPredFlag);
 #if DEBUG
   Yap_InitCPred ("write_string", 2, p_write_string, SyncPredFlag|UserCPredFlag);
 #endif
-  Yap_InitCPred ("$start_line", 1, p_startline, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$change_type_of_char", 2, p_change_type_of_char, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$type_of_char", 2, p_type_of_char, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred ("$start_line", 1, p_startline, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$change_type_of_char", 2, p_change_type_of_char, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$type_of_char", 2, p_type_of_char, SafePredFlag|SyncPredFlag);
   Yap_InitCPred ("char_conversion", 2, p_char_conversion, SyncPredFlag);
-  Yap_InitCPred ("$current_char_conversion", 2, p_current_char_conversion, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$all_char_conversions", 1, p_all_char_conversions, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$force_char_conversion", 0, p_force_char_conversion, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$disable_char_conversion", 0, p_disable_char_conversion, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred ("$current_char_conversion", 2, p_current_char_conversion, SyncPredFlag);
+  Yap_InitCPred ("$all_char_conversions", 1, p_all_char_conversions, SyncPredFlag);
+  Yap_InitCPred ("$force_char_conversion", 0, p_force_char_conversion, SyncPredFlag);
+  Yap_InitCPred ("$disable_char_conversion", 0, p_disable_char_conversion, SyncPredFlag);
 #if HAVE_SELECT
     //  Yap_InitCPred ("stream_select", 3, p_stream_select, SafePredFlag|SyncPredFlag);
 #endif
-  Yap_InitCPred ("$float_format", 1, p_float_format, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred ("$float_format", 1, p_float_format, SafePredFlag|SyncPredFlag);
 
 }
diff --git a/C/load_foreign.c b/C/load_foreign.c
index b0d39fad8..4d96f19b4 100644
--- a/C/load_foreign.c
+++ b/C/load_foreign.c
@@ -229,12 +229,12 @@ Yap_InitLoadForeign( void )
     Yap_FindExecutable("yap");
   else
     Yap_FindExecutable(GLOBAL_argv[0]);
-  Yap_InitCPred("$load_foreign_files", 3, p_load_foreign, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$open_shared_objects", 0, p_open_shared_objects, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$open_shared_object", 3, p_open_shared_object, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$load_foreign_files", 3, p_load_foreign, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$open_shared_objects", 0, p_open_shared_objects, SafePredFlag);
+  Yap_InitCPred("$open_shared_object", 3, p_open_shared_object, SyncPredFlag);
   Yap_InitCPred("close_shared_object", 1, p_close_shared_object, SyncPredFlag|SafePredFlag);
   Yap_InitCPred("call_shared_object_function", 2, p_call_shared_object_function, SyncPredFlag);
-  Yap_InitCPred("$obj_suffix", 1, p_obj_suffix, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$obj_suffix", 1, p_obj_suffix, SafePredFlag);
 }
 
 void 
diff --git a/C/modules.c b/C/modules.c
index 0c9e64b16..f6ec73135 100644
--- a/C/modules.c
+++ b/C/modules.c
@@ -301,13 +301,13 @@ Yap_StripModule(Term t,  Term *modp)
 void 
 Yap_InitModulesC(void)
 {
-  Yap_InitCPred("$current_module", 2, p_current_module, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$current_module", 1, p_current_module1, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$change_module", 1, p_change_module, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("strip_module", 3, p_strip_module, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$current_module", 2, p_current_module, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$current_module", 1, p_current_module1, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$change_module", 1, p_change_module, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("strip_module", 3, p_strip_module, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("context_module", 1, p_context_module, 0);
   Yap_InitCPredBack("$all_current_modules", 1, 1, init_current_module, cont_current_module,
-		SafePredFlag|SyncPredFlag|HiddenPredFlag);
+		SafePredFlag|SyncPredFlag);
 }
 
 
diff --git a/C/qlyr.c b/C/qlyr.c
index 6e12eeb2b..c4c0b0ef3 100644
--- a/C/qlyr.c
+++ b/C/qlyr.c
@@ -934,6 +934,9 @@ read_pred(IOSTREAM *stream, Term mod) {
   if (flags & MultiFileFlag && ap->ModuleOfPred == PROLOG_MODULE)
     ap->ModuleOfPred = TermProlog;
   read_clauses(stream, ap, nclauses, flags);
+  if (flags & HiddenPredFlag) {
+    Yap_HidePred(ap);
+  }
 }
 
 static void
@@ -1054,8 +1057,8 @@ Yap_Restore(char *s, char *lib_dir)
 
 void Yap_InitQLYR(void)
 {
-  Yap_InitCPred("$qload_module_preds", 1, p_read_module_preds, SyncPredFlag|HiddenPredFlag|UserCPredFlag);
-  Yap_InitCPred("$qload_program", 1, p_read_program, SyncPredFlag|HiddenPredFlag|UserCPredFlag);
+  Yap_InitCPred("$qload_module_preds", 1, p_read_module_preds, SyncPredFlag|UserCPredFlag);
+  Yap_InitCPred("$qload_program", 1, p_read_program, SyncPredFlag|UserCPredFlag);
   if (FALSE) {
     restore_codes();
   }
diff --git a/C/qlyw.c b/C/qlyw.c
index c7a872d80..b00b923fb 100644
--- a/C/qlyw.c
+++ b/C/qlyw.c
@@ -898,8 +898,8 @@ p_save_program( USES_REGS1 )
 
 void Yap_InitQLY(void)
 {
-  Yap_InitCPred("$qsave_module_preds", 2, p_save_module_preds, SyncPredFlag|HiddenPredFlag|UserCPredFlag);
-  Yap_InitCPred("$qsave_program", 1, p_save_program, SyncPredFlag|HiddenPredFlag|UserCPredFlag);
+  Yap_InitCPred("$qsave_module_preds", 2, p_save_module_preds, SyncPredFlag|UserCPredFlag);
+  Yap_InitCPred("$qsave_program", 1, p_save_program, SyncPredFlag|UserCPredFlag);
   if (FALSE) {
     restore_codes();
   }
diff --git a/C/save.c b/C/save.c
index 28960b8ed..416e812a7 100755
--- a/C/save.c
+++ b/C/save.c
@@ -1843,7 +1843,7 @@ p_restore( USES_REGS1 )
 void 
 Yap_InitSavePreds(void)
 {
-  Yap_InitCPred("$save", 2, p_save2, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$save_program", 1, p_save_program, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$restore", 1, p_restore, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$save", 2, p_save2, SyncPredFlag);
+  Yap_InitCPred("$save_program", 1, p_save_program, SyncPredFlag);
+  Yap_InitCPred("$restore", 1, p_restore, SyncPredFlag);
 }
diff --git a/C/sort.c b/C/sort.c
index 6b2d06617..a22f339d2 100644
--- a/C/sort.c
+++ b/C/sort.c
@@ -415,7 +415,7 @@ p_ksort( USES_REGS1 )
 void 
 Yap_InitSortPreds(void)
 {
-  Yap_InitCPred("$sort", 2, p_sort, HiddenPredFlag);
-  Yap_InitCPred("$msort", 2, p_msort, HiddenPredFlag);
-  Yap_InitCPred("$keysort", 2, p_ksort, HiddenPredFlag);
+  Yap_InitCPred("$sort", 2, p_sort, 0);
+  Yap_InitCPred("$msort", 2, p_msort, 0);
+  Yap_InitCPred("$keysort", 2, p_ksort, 0);
 }
diff --git a/C/stdpreds.c b/C/stdpreds.c
index 1e3118e87..b4da79f74 100644
--- a/C/stdpreds.c
+++ b/C/stdpreds.c
@@ -4395,19 +4395,19 @@ void
 Yap_InitBackCPreds(void)
 {
   Yap_InitCPredBack("$current_atom", 1, 2, init_current_atom, cont_current_atom,
-		SafePredFlag|SyncPredFlag|HiddenPredFlag);
+		SafePredFlag|SyncPredFlag);
   Yap_InitCPredBack("$current_wide_atom", 1, 2, init_current_wide_atom,
 		    cont_current_wide_atom,
-		    SafePredFlag|SyncPredFlag|HiddenPredFlag);
+		    SafePredFlag|SyncPredFlag);
   Yap_InitCPredBack("$current_predicate", 3, 1, init_current_predicate, cont_current_predicate,
-		SafePredFlag|SyncPredFlag|HiddenPredFlag);
+		SafePredFlag|SyncPredFlag);
   Yap_InitCPredBack("$current_predicate_for_atom", 3, 1, init_current_predicate_for_atom, cont_current_predicate_for_atom,
-		SafePredFlag|SyncPredFlag|HiddenPredFlag);
+		SafePredFlag|SyncPredFlag);
   Yap_InitCPredBack("$current_op", 5, 1, init_current_op, cont_current_op,
 		SafePredFlag|SyncPredFlag);
   Yap_InitCPredBack("$current_atom_op", 5, 1, init_current_atom_op, cont_current_atom_op,
 		SafePredFlag|SyncPredFlag);
-  Yap_InitCPredBack("$sub_atom_fetch", 5, 5, init_sub_atom_fetch, cont_sub_atom_fetch, HiddenPredFlag);
+  Yap_InitCPredBack("$sub_atom_fetch", 5, 5, init_sub_atom_fetch, cont_sub_atom_fetch, 0);
 #ifdef BEAM
   Yap_InitCPredBack("eam", 1, 0, start_eam, cont_eam,
 		SafePredFlag);
@@ -4452,9 +4452,9 @@ Yap_InitCPreds(void)
   /* numerical comparison */
   Yap_InitCPred("set_value", 2, p_setval, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("get_value", 2, p_value, TestPredFlag|SafePredFlag|SyncPredFlag);
-  Yap_InitCPred("$values", 3, p_values, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$values", 3, p_values, SafePredFlag|SyncPredFlag);
   /* general purpose */
-  Yap_InitCPred("$opdec", 4, p_opdec, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$opdec", 4, p_opdec, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("name", 2, p_name, 0);
   Yap_InitCPred("string_to_atom", 2, p_string_to_atom, 0);
   Yap_InitCPred("string_to_list", 2, p_string_to_list, 0);
@@ -4462,8 +4462,8 @@ Yap_InitCPreds(void)
   Yap_InitCPred("atom_chars", 2, p_atom_chars, 0);
   Yap_InitCPred("atom_codes", 2, p_atom_codes, 0);
   Yap_InitCPred("atom_length", 2, p_atom_length, SafePredFlag);
-  Yap_InitCPred("$atom_split", 4, p_atom_split, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$sub_atom_extract", 5, p_sub_atom_extract, HiddenPredFlag);
+  Yap_InitCPred("$atom_split", 4, p_atom_split, SafePredFlag);
+  Yap_InitCPred("$sub_atom_extract", 5, p_sub_atom_extract, 0);
   Yap_InitCPred("number_chars", 2, p_number_chars, 0);
   Yap_InitCPred("number_atom", 2, p_number_atom, 0);
   Yap_InitCPred("number_codes", 2, p_number_codes, 0);
@@ -4471,28 +4471,28 @@ Yap_InitCPreds(void)
   Yap_InitCPred("atom_concat", 2, p_atom_concat, 0);
   Yap_InitCPred("atomic_concat", 2, p_atomic_concat, 0);
   Yap_InitCPred("=..", 2, p_univ, 0);
-  Yap_InitCPred("$statistics_trail_max", 1, p_statistics_trail_max, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_heap_max", 1, p_statistics_heap_max, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_global_max", 1, p_statistics_global_max, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_local_max", 1, p_statistics_local_max, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_heap_info", 2, p_statistics_heap_info, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_stacks_info", 3, p_statistics_stacks_info, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_trail_info", 2, p_statistics_trail_info, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_atom_info", 2, p_statistics_atom_info, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_db_size", 4, p_statistics_db_size, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$statistics_lu_db_size", 5, p_statistics_lu_db_size, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$argv", 1, p_argv, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$executable", 1, p_executable, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$runtime", 2, p_runtime, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$cputime", 2, p_cputime, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$systime", 2, p_systime, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$walltime", 2, p_walltime, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$access_yap_flags", 2, p_access_yap_flags, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$set_yap_flags", 2, p_set_yap_flags, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$p_system_mode", 1, p_system_mode, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$statistics_trail_max", 1, p_statistics_trail_max, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_heap_max", 1, p_statistics_heap_max, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_global_max", 1, p_statistics_global_max, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_local_max", 1, p_statistics_local_max, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_heap_info", 2, p_statistics_heap_info, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_stacks_info", 3, p_statistics_stacks_info, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_trail_info", 2, p_statistics_trail_info, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_atom_info", 2, p_statistics_atom_info, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_db_size", 4, p_statistics_db_size, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$statistics_lu_db_size", 5, p_statistics_lu_db_size, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$argv", 1, p_argv, SafePredFlag);
+  Yap_InitCPred("$executable", 1, p_executable, SafePredFlag);
+  Yap_InitCPred("$runtime", 2, p_runtime, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$cputime", 2, p_cputime, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$systime", 2, p_systime, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$walltime", 2, p_walltime, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$access_yap_flags", 2, p_access_yap_flags, SafePredFlag);
+  Yap_InitCPred("$set_yap_flags", 2, p_set_yap_flags, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$p_system_mode", 1, p_system_mode, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("abort", 0, p_abort, SyncPredFlag);
-  Yap_InitCPred("$max_tagged_integer", 1, p_max_tagged_integer, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$min_tagged_integer", 1, p_min_tagged_integer, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$max_tagged_integer", 1, p_max_tagged_integer, SafePredFlag);
+  Yap_InitCPred("$min_tagged_integer", 1, p_min_tagged_integer, SafePredFlag);
 #ifdef BEAM
   Yap_InitCPred("@", 0, eager_split, SafePredFlag);
   Yap_InitCPred(":", 0, force_wait, SafePredFlag);
@@ -4502,33 +4502,33 @@ Yap_InitCPreds(void)
   Yap_InitCPred("eamtime", 0, show_time, SafePredFlag);
   Yap_InitCPred("eam", 0, use_eam, SafePredFlag);
 #endif
-  Yap_InitCPred("$halt", 1, p_halt, SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$lock_system", 0, p_lock_system, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$unlock_system", 0, p_unlock_system, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$enter_undefp", 0, p_enterundefp, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$exit_undefp", 0, p_exitundefp, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$halt", 1, p_halt, SyncPredFlag);
+  Yap_InitCPred("$lock_system", 0, p_lock_system, SafePredFlag);
+  Yap_InitCPred("$unlock_system", 0, p_unlock_system, SafePredFlag);
+  Yap_InitCPred("$enter_undefp", 0, p_enterundefp, SafePredFlag);
+  Yap_InitCPred("$exit_undefp", 0, p_exitundefp, SafePredFlag);
   /* basic predicates for the prolog machine tracer */
   /* they are defined in analyst.c */
   /* Basic predicates for the debugger */
-  Yap_InitCPred("$creep", 0, p_creep, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$signal_creep", 0, p_signal_creep, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$disable_creep", 0, p_disable_creep, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$disable_docreep", 0, p_disable_docreep, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$do_not_creep", 0, p_stop_creep, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$creep", 0, p_creep, SafePredFlag);
+  Yap_InitCPred("$signal_creep", 0, p_signal_creep, SafePredFlag);
+  Yap_InitCPred("$disable_creep", 0, p_disable_creep, SafePredFlag);
+  Yap_InitCPred("$disable_docreep", 0, p_disable_docreep, SafePredFlag);
+  Yap_InitCPred("$do_not_creep", 0, p_stop_creep, SafePredFlag|SyncPredFlag);
 #ifdef DEBUG
-  Yap_InitCPred("$debug", 1, p_debug, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$debug", 1, p_debug, SafePredFlag|SyncPredFlag);
 #endif
   /* Accessing and changing the flags for a predicate */
-  Yap_InitCPred("$flags", 4, p_flags, SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$flags", 4, p_flags, SyncPredFlag);
   /* hiding and unhiding some predicates */
   Yap_InitCPred("hide", 1, p_hide, SafePredFlag|SyncPredFlag);
   Yap_InitCPred("unhide", 1, p_unhide, SafePredFlag|SyncPredFlag);
-  Yap_InitCPred("$hidden", 1, p_hidden, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$has_yap_or", 0, p_has_yap_or, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred("$has_eam", 0, p_has_eam, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$hidden", 1, p_hidden, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$has_yap_or", 0, p_has_yap_or, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$has_eam", 0, p_has_eam, SafePredFlag|SyncPredFlag);
 #ifndef YAPOR
   Yap_InitCPred("parallel_mode", 1, p_parallel_mode, SafePredFlag|SyncPredFlag);
-  Yap_InitCPred("$c_yapor_workers", 1, p_yapor_workers, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred("$c_yapor_workers", 1, p_yapor_workers, SafePredFlag|SyncPredFlag);
 #endif /* YAPOR */
 #ifdef INES
   Yap_InitCPred("euc_dist", 3, p_euc_dist, SafePredFlag);
diff --git a/C/sysbits.c b/C/sysbits.c
index a5f54a447..2d72dd135 100755
--- a/C/sysbits.c
+++ b/C/sysbits.c
@@ -3226,18 +3226,18 @@ Yap_InitSysPreds(void)
   InitLastWtime();
   Yap_InitCPred ("srandom", 1, p_srandom, SafePredFlag);
   Yap_InitCPred ("sh", 0, p_sh, SafePredFlag|SyncPredFlag);
-  Yap_InitCPred ("$shell", 1, p_shell, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred ("$shell", 1, p_shell, SafePredFlag|SyncPredFlag);
   Yap_InitCPred ("system", 1, p_system, SafePredFlag|SyncPredFlag);
   Yap_InitCPred ("rename", 2, p_mv, SafePredFlag|SyncPredFlag);
-  Yap_InitCPred ("$yap_home", 1, p_yap_home, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$dir_separator", 1, p_dir_sp, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$alarm", 4, p_alarm, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$getenv", 2, p_getenv, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$putenv", 2, p_putenv, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$set_fpu_exceptions", 0, p_set_fpu_exceptions, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$first_signal", 1, p_first_signal, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$host_type", 1, p_host_type, SafePredFlag|SyncPredFlag|HiddenPredFlag);
-  Yap_InitCPred ("$continue_signals", 0, p_continue_signals, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred ("$yap_home", 1, p_yap_home, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$dir_separator", 1, p_dir_sp, SafePredFlag);
+  Yap_InitCPred ("$alarm", 4, p_alarm, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$getenv", 2, p_getenv, SafePredFlag);
+  Yap_InitCPred ("$putenv", 2, p_putenv, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$set_fpu_exceptions", 0, p_set_fpu_exceptions, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$first_signal", 1, p_first_signal, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$host_type", 1, p_host_type, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$continue_signals", 0, p_continue_signals, SafePredFlag|SyncPredFlag);
   Yap_InitCPred ("$env_separator", 1, p_env_separator, SafePredFlag);
   Yap_InitCPred ("$unix", 0, p_unix, SafePredFlag);
   Yap_InitCPred ("$win32", 0, p_win32, SafePredFlag);
@@ -3247,7 +3247,7 @@ Yap_InitSysPreds(void)
   Yap_InitCPred ("win_registry_get_value", 3, p_win_registry_get_value,0);
 #endif
   CurrentModule = HACKS_MODULE;
-  Yap_InitCPred ("virtual_alarm", 4, p_virtual_alarm, SafePredFlag|SyncPredFlag|HiddenPredFlag);
+  Yap_InitCPred ("virtual_alarm", 4, p_virtual_alarm, SafePredFlag|SyncPredFlag);
   Yap_InitCPred ("enable_interrupts", 0, p_enable_interrupts, SafePredFlag);
   Yap_InitCPred ("disable_interrupts", 0, p_disable_interrupts, SafePredFlag);
   CurrentModule = OPERATING_SYSTEM_MODULE;
diff --git a/C/threads.c b/C/threads.c
index fd6cd59f5..8a4f253c2 100755
--- a/C/threads.c
+++ b/C/threads.c
@@ -949,41 +949,41 @@ p_thread_unlock( USES_REGS1 )
 
 void Yap_InitThreadPreds(void)
 {
-  Yap_InitCPred("$no_threads", 0, p_no_threads, HiddenPredFlag);
-  Yap_InitCPred("$max_workers", 1, p_max_workers, HiddenPredFlag);
-  Yap_InitCPred("$max_threads", 1, p_max_threads, HiddenPredFlag);
-  Yap_InitCPred("$thread_new_tid", 1, p_thread_new_tid, HiddenPredFlag);
-  Yap_InitCPred("$create_thread", 7, p_create_thread, HiddenPredFlag);
-  Yap_InitCPred("$thread_self", 1, p_thread_self, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_status_lock", 1, p_thread_status_lock, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_status_unlock", 1, p_thread_status_unlock, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_zombie_self", 1, p_thread_zombie_self, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_join", 1, p_thread_join, HiddenPredFlag);
-  Yap_InitCPred("$thread_destroy", 1, p_thread_destroy, HiddenPredFlag);
+  Yap_InitCPred("$no_threads", 0, p_no_threads, 0);
+  Yap_InitCPred("$max_workers", 1, p_max_workers, 0);
+  Yap_InitCPred("$max_threads", 1, p_max_threads, 0);
+  Yap_InitCPred("$thread_new_tid", 1, p_thread_new_tid, 0);
+  Yap_InitCPred("$create_thread", 7, p_create_thread, 0);
+  Yap_InitCPred("$thread_self", 1, p_thread_self, SafePredFlag);
+  Yap_InitCPred("$thread_status_lock", 1, p_thread_status_lock, SafePredFlag);
+  Yap_InitCPred("$thread_status_unlock", 1, p_thread_status_unlock, SafePredFlag);
+  Yap_InitCPred("$thread_zombie_self", 1, p_thread_zombie_self, SafePredFlag);
+  Yap_InitCPred("$thread_join", 1, p_thread_join, 0);
+  Yap_InitCPred("$thread_destroy", 1, p_thread_destroy, 0);
   Yap_InitCPred("thread_yield", 0, p_thread_yield, 0);
-  Yap_InitCPred("$detach_thread", 1, p_thread_detach, HiddenPredFlag);
-  Yap_InitCPred("$thread_detached", 1, p_thread_detached, HiddenPredFlag);
-  Yap_InitCPred("$thread_detached", 2, p_thread_detached2, HiddenPredFlag);
-  Yap_InitCPred("$thread_exit", 0, p_thread_exit, HiddenPredFlag);
+  Yap_InitCPred("$detach_thread", 1, p_thread_detach, 0);
+  Yap_InitCPred("$thread_detached", 1, p_thread_detached, 0);
+  Yap_InitCPred("$thread_detached", 2, p_thread_detached2, 0);
+  Yap_InitCPred("$thread_exit", 0, p_thread_exit, 0);
   Yap_InitCPred("thread_setconcurrency", 2, p_thread_set_concurrency, 0);
-  Yap_InitCPred("$valid_thread", 1, p_valid_thread, HiddenPredFlag);
-  Yap_InitCPred("$new_mutex", 1, p_new_mutex, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$destroy_mutex", 1, p_destroy_mutex, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$lock_mutex", 1, p_lock_mutex, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$trylock_mutex", 1, p_trylock_mutex, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$unlock_mutex", 1, p_unlock_mutex, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$mutex_info", 3, p_mutex_info, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$cond_create", 1, p_cond_create, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$cond_destroy", 1, p_cond_destroy, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$cond_signal", 1, p_cond_signal, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$cond_broadcast", 1, p_cond_broadcast, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$cond_wait", 2, p_cond_wait, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_stacks", 4, p_thread_stacks, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$signal_thread", 1, p_thread_signal, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$nof_threads", 1, p_nof_threads, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$nof_threads_created", 1, p_nof_threads_created, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_sleep", 4, p_thread_sleep, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_runtime", 1, p_thread_runtime, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$valid_thread", 1, p_valid_thread, 0);
+  Yap_InitCPred("$new_mutex", 1, p_new_mutex, SafePredFlag);
+  Yap_InitCPred("$destroy_mutex", 1, p_destroy_mutex, SafePredFlag);
+  Yap_InitCPred("$lock_mutex", 1, p_lock_mutex, SafePredFlag);
+  Yap_InitCPred("$trylock_mutex", 1, p_trylock_mutex, SafePredFlag);
+  Yap_InitCPred("$unlock_mutex", 1, p_unlock_mutex, SafePredFlag);
+  Yap_InitCPred("$mutex_info", 3, p_mutex_info, SafePredFlag);
+  Yap_InitCPred("$cond_create", 1, p_cond_create, SafePredFlag);
+  Yap_InitCPred("$cond_destroy", 1, p_cond_destroy, SafePredFlag);
+  Yap_InitCPred("$cond_signal", 1, p_cond_signal, SafePredFlag);
+  Yap_InitCPred("$cond_broadcast", 1, p_cond_broadcast, SafePredFlag);
+  Yap_InitCPred("$cond_wait", 2, p_cond_wait, SafePredFlag);
+  Yap_InitCPred("$thread_stacks", 4, p_thread_stacks, SafePredFlag);
+  Yap_InitCPred("$signal_thread", 1, p_thread_signal, SafePredFlag);
+  Yap_InitCPred("$nof_threads", 1, p_nof_threads, SafePredFlag);
+  Yap_InitCPred("$nof_threads_created", 1, p_nof_threads_created, SafePredFlag);
+  Yap_InitCPred("$thread_sleep", 4, p_thread_sleep, SafePredFlag);
+  Yap_InitCPred("$thread_runtime", 1, p_thread_runtime, SafePredFlag);
   Yap_InitCPred("$thread_self_lock", 1, p_thread_self_lock, SafePredFlag);
   Yap_InitCPred("$thread_run_at_exit", 2, p_thread_atexit, SafePredFlag);
   Yap_InitCPred("$thread_unlock", 1, p_thread_unlock, SafePredFlag);
@@ -1047,14 +1047,14 @@ p_max_workers(void)
 
 void Yap_InitThreadPreds(void)
 {
-  Yap_InitCPred("$max_workers", 1, p_max_workers, HiddenPredFlag);
-  Yap_InitCPred("$thread_self", 1, p_thread_self, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$no_threads", 0, p_no_threads, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$max_threads", 1, p_max_threads, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$nof_threads", 1, p_nof_threads, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$nof_threads_created", 1, p_nof_threads_created, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_stacks", 4, p_thread_stacks, SafePredFlag|HiddenPredFlag);
-  Yap_InitCPred("$thread_runtime", 1, p_thread_runtime, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$max_workers", 1, p_max_workers, 0);
+  Yap_InitCPred("$thread_self", 1, p_thread_self, SafePredFlag);
+  Yap_InitCPred("$no_threads", 0, p_no_threads, SafePredFlag);
+  Yap_InitCPred("$max_threads", 1, p_max_threads, SafePredFlag);
+  Yap_InitCPred("$nof_threads", 1, p_nof_threads, SafePredFlag);
+  Yap_InitCPred("$nof_threads_created", 1, p_nof_threads_created, SafePredFlag);
+  Yap_InitCPred("$thread_stacks", 4, p_thread_stacks, SafePredFlag);
+  Yap_InitCPred("$thread_runtime", 1, p_thread_runtime, SafePredFlag);
   Yap_InitCPred("$thread_unlock", 1, p_thread_unlock, SafePredFlag);
 }
 
diff --git a/C/utilpreds.c b/C/utilpreds.c
index df5c48ea1..2ec52e4ef 100644
--- a/C/utilpreds.c
+++ b/C/utilpreds.c
@@ -5195,8 +5195,8 @@ void Yap_InitUtilCPreds(void)
   Yap_InitCPred("duplicate_term", 2, p_duplicate_term, 0);
   Yap_InitCPred("copy_term_nat", 2, p_copy_term_no_delays, 0);
   Yap_InitCPred("ground", 1, p_ground, SafePredFlag);
-  Yap_InitCPred("$variables_in_term", 3, p_variables_in_term, HiddenPredFlag);
-  Yap_InitCPred("$non_singletons_in_term", 3, p_non_singletons_in_term, HiddenPredFlag);
+  Yap_InitCPred("$variables_in_term", 3, p_variables_in_term, 0);
+  Yap_InitCPred("$non_singletons_in_term", 3, p_non_singletons_in_term, 0);
   Yap_InitCPred("term_variables", 2, p_term_variables, 0);
   Yap_InitCPred("term_variables", 3, p_term_variables3, 0);
   Yap_InitCPred("term_attvars", 2, p_term_attvars, 0);
@@ -5224,7 +5224,7 @@ void Yap_InitUtilCPreds(void)
   Yap_InitCPred("import_term", 2, p_import_term, 0);
   CurrentModule = cm;
 #ifdef DEBUG
-  Yap_InitCPred("$force_trail_expansion", 1, p_force_trail_expansion, SafePredFlag|HiddenPredFlag);
+  Yap_InitCPred("$force_trail_expansion", 1, p_force_trail_expansion, SafePredFlag);
   Yap_InitCPred("dum", 1, camacho_dum, SafePredFlag);
 #endif
 }
diff --git a/H/Yapproto.h b/H/Yapproto.h
index 7cdf160c2..b46c64fee 100644
--- a/H/Yapproto.h
+++ b/H/Yapproto.h
@@ -137,6 +137,7 @@ void	STD_PROTO(Yap_BuildMegaClause,(struct pred_entry *));
 void	STD_PROTO(Yap_EraseMegaClause,(yamop *,struct pred_entry *));
 void	STD_PROTO(Yap_ResetConsultStack,(void));
 void	STD_PROTO(Yap_AssertzClause,(struct pred_entry *, yamop *));
+void    Yap_HidePred(struct pred_entry *pe);
 
 
 /* cmppreds.c */
diff --git a/H/dhstruct.h b/H/dhstruct.h
index a33b6bb4d..6d208d9ab 100644
--- a/H/dhstruct.h
+++ b/H/dhstruct.h
@@ -100,6 +100,8 @@
 #define SWI_MODULE Yap_heap_regs->swi_module
 #define DBLOAD_MODULE Yap_heap_regs->dbload_module
 
+#define HIDDEN_PREDICATES Yap_heap_regs->hidden_predicates
+
 
 
 #define CurrentModules Yap_heap_regs->current_modules
diff --git a/H/hstruct.h b/H/hstruct.h
index 5dd6f25c2..03b51954d 100644
--- a/H/hstruct.h
+++ b/H/hstruct.h
@@ -100,6 +100,8 @@
   Term  swi_module;
   Term  dbload_module;
 
+  Prop  hidden_predicates;
+
 
 
   struct mod_entry  *current_modules;
diff --git a/H/ihstruct.h b/H/ihstruct.h
index 3ffc74630..06fab5deb 100644
--- a/H/ihstruct.h
+++ b/H/ihstruct.h
@@ -100,6 +100,8 @@
   SWI_MODULE = MkAtomTerm(AtomSwi);
   DBLOAD_MODULE = MkAtomTerm(AtomDBLoad);
 
+  HIDDEN_PREDICATES = NULL;
+
 
 
   CurrentModules = NULL;
diff --git a/H/rheap.h b/H/rheap.h
index 290210a52..59e2d1245 100644
--- a/H/rheap.h
+++ b/H/rheap.h
@@ -726,6 +726,14 @@ RestoreSWIBlobs__( USES_REGS1 )
   RestoreAtomList(SWI_Blobs PASS_REGS);
 }
 
+static void
+RestoreHidenPredicates( USES_REGS1 )
+{
+  HIDDEN_PREDICATES = PropAdjust(HIDDEN_PREDICATES);
+  RestoreEntries(HIDDEN_PREDICATES, TRUE PASS_REGS);
+}
+
+
 static void
 RestorePredHash__( USES_REGS1 )
 {
diff --git a/H/rhstruct.h b/H/rhstruct.h
index 485a6ed5e..4b84266e4 100644
--- a/H/rhstruct.h
+++ b/H/rhstruct.h
@@ -100,6 +100,8 @@
   SWI_MODULE = AtomTermAdjust(SWI_MODULE);
   DBLOAD_MODULE = AtomTermAdjust(DBLOAD_MODULE);
 
+  RestoreHidenPredicates();
+
 
 
   CurrentModules = ModEntryPtrAdjust(CurrentModules);
diff --git a/misc/GLOBALS b/misc/GLOBALS
index aa69e10e6..4ab35df87 100644
--- a/misc/GLOBALS
+++ b/misc/GLOBALS
@@ -89,6 +89,9 @@ Int 				tot_agc_time 				=0
 /* number of heap objects in all garbage collections */
 Int 				tot_agc_recovered 			=0 
 
+// hidden predicates
+struct PropEntryStruct *	hidden_predicates			=NULL
+
 //arrays.c
 #if HAVE_MMAP
 struct MMAP_ARRAY_BLOCK* 	mmap_arrays 				=NULL
diff --git a/misc/HEAPFIELDS b/misc/HEAPFIELDS
index ecb62bc9a..597bd4e6b 100644
--- a/misc/HEAPFIELDS
+++ b/misc/HEAPFIELDS
@@ -102,6 +102,9 @@ Term		globals_module		GLOBALS_MODULE		MkAT AtomNb
 Term		swi_module		SWI_MODULE		MkAT AtomSwi
 Term		dbload_module		DBLOAD_MODULE		MkAT AtomDBLoad
 
+// hidden predicates
+Prop		hidden_predicates	HIDDEN_PREDICATES	=NULL RestoreHidenPredicates()
+
 //
 // Module list
 //
diff --git a/pl/flags.yap b/pl/flags.yap
index 99ef38c95..a08d937d5 100755
--- a/pl/flags.yap
+++ b/pl/flags.yap
@@ -647,7 +647,7 @@ yap_flag(update_semantics,X) :-
 
 yap_flag(toplevel_hook,G) :-
 	var(G), !,
-	( recorded('$toplevel_hooks',G,_) -> G ; G = false ).
+	( recorded('$toplevel_hooks',G,_) -> G ; G = fail ).
 yap_flag(toplevel_hook,G) :- !,
 	'$set_toplevel_hook'(G).
 
diff --git a/pl/protect.yap b/pl/protect.yap
index aa32a7f23..d4058f2c4 100755
--- a/pl/protect.yap
+++ b/pl/protect.yap
@@ -20,7 +20,7 @@
 '$protect' :-
 	current_atom(Name),
 	atom_codes(Name,[0'$|_]),
-	'$hide_predicates'(Name),
+%	'$hide_predicates'(Name),
 	'$hide'(Name).
 '$protect' :-
 	'$hide_predicates'(bootstrap),