From d18c67aa2a2e760273b21fcface127bd57382485 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADtor=20Santos=20Costa?= <vsc@dcc.fc.up.pt>
Date: Fri, 8 Feb 2013 10:35:40 -0600
Subject: [PATCH 1/4] try to reset stack

---
 console/yap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/console/yap.c b/console/yap.c
index d067acee9..fd5ed46a6 100755
--- a/console/yap.c
+++ b/console/yap.c
@@ -166,7 +166,7 @@ main (int argc, char **argv)
       YAP_RunGoalOnce(t_goal);
     }
   }
-  YAP_ClearExceptions();
+  YAP_Reset();
   /* End preprocessor code */
 
   exec_top_level(BootMode, &init_args);

From 046cb5f8d6b079dddeed535ec8244e780dc1321b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADtor=20Santos=20Costa?= <vsc@dcc.fc.up.pt>
Date: Fri, 8 Feb 2013 10:36:45 -0600
Subject: [PATCH 2/4] debugging

---
 C/absmi.c         |  26 ----
 C/c_interface.c   |  23 +--
 C/cdmgr.c         |   1 +
 C/exec.c          |  77 +++-------
 C/signals.c       | 381 ++++++++++++++++++++++++++++++++++++++++++++++
 C/stdpreds.c      | 225 +--------------------------
 C/sysbits.c       | 203 ------------------------
 H/Yapproto.h      |   7 +-
 pl/attributes.yap |   8 +-
 pl/boot.yap       | 105 +++++++------
 pl/consult.yap    |   8 +-
 pl/control.yap    |  31 ----
 pl/debug.yap      | 114 ++++++++------
 pl/errors.yap     |   8 +-
 pl/hacks.yap      |   1 +
 pl/modules.yap    |   2 +-
 pl/signals.yap    | 131 ++--------------
 17 files changed, 573 insertions(+), 778 deletions(-)
 create mode 100644 C/signals.c

diff --git a/C/absmi.c b/C/absmi.c
index f64ef6ae6..8a95d799c 100755
--- a/C/absmi.c
+++ b/C/absmi.c
@@ -512,26 +512,6 @@ Term Yap_XREGS[MaxTemps];	/* 29                                     */
 
 #include "arith2.h"
 
-/*
-  I can creep if I am not a prolog builtin that has been called
-  by a prolog builtin,
-  exception: meta-calls
-*/
-static PredEntry *
-creep_allowed(PredEntry *p, PredEntry *p0)
-{
-  if (!p0)
-    return NULL;
-  if (p0 == PredMetaCall)
-    return p0;
-  if (!p0->ModuleOfPred && 
-      (!p ||
-       !p->ModuleOfPred ||
-       p->PredFlags & StandardPredFlag))
-    return NULL;
-  return p;
-}
-
 #ifdef COROUTINING
 /*
   Imagine we are interrupting the execution, say, because we have a spy
@@ -2868,11 +2848,6 @@ Yap_absmi(int inp)
 	  CreepFlag = CalculateStackGap();
 	goto fail;
       }
-      if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
-	PredEntry *ap = PREG->u.Osbpp.p;
-	SREG = (CELL *) ap;
-	goto creepc;
-      }
       SREG = (CELL *) PREG->u.Osbpp.p;
       if (LOCAL_ActiveSignals & YAP_CDOVF_SIGNAL) {
 	SET_ASP(YREG, PREG->u.Osbpp.s);
@@ -3331,7 +3306,6 @@ Yap_absmi(int inp)
       /* tell whether we can creep or not, this is hard because we will
 	 lose the info RSN
       */
-      PP = creep_allowed((PredEntry*)SREG,PP);
       BEGD(d0);
       d0 = ((PredEntry *)(SREG))->ArityOfPE;
       if (d0 == 0) {
diff --git a/C/c_interface.c b/C/c_interface.c
index e5952e877..27b85ceac 100644
--- a/C/c_interface.c
+++ b/C/c_interface.c
@@ -3240,28 +3240,29 @@ X_API int
 YAP_Reset(void)
 {
   CACHE_REGS
+  int res = TRUE;
 #ifndef THREADS
   int worker_id = 0;
 #endif
   BACKUP_MACHINE_REGS();
 
+  YAP_ClearExceptions();
   /* first, backtrack to the root */
-  if (B != NULL) {
-    while (B->cp_b != NULL)
-      B = B->cp_b;
+  while (B->cp_b) {
+    B = B->cp_b;
     P = FAILCODE;
-    if (Yap_exec_absmi(0) != 0) {
-      GLOBAL_Initialised = TRUE;
-
-      Yap_InitYaamRegs( worker_id );
-      RECOVER_MACHINE_REGS();
-      return FALSE;
-    }
+    res = Yap_exec_absmi(0);
   }
   /* reinitialise the engine */
   //  Yap_InitYaamRegs( worker_id );
   GLOBAL_Initialised = TRUE;
-
+  ENV = LCL0;
+  ASP = B;
+  /* the first real choice-point will also have AP=FAIL */ 
+  /* always have an empty slots for people to use */
+  CurSlot = 0;
+  Yap_StartSlots( PASS_REGS1 );
+  P = CP = YESCODE;
   RECOVER_MACHINE_REGS();
   return(TRUE);
 }
diff --git a/C/cdmgr.c b/C/cdmgr.c
index 4e0ab65ba..9dd938664 100644
--- a/C/cdmgr.c
+++ b/C/cdmgr.c
@@ -5667,6 +5667,7 @@ p_cpc_info( USES_REGS1 )
   PredEntry *pe;
   yamop *ipc = (yamop *)IntegerOfTerm(Deref(ARG1));
 
+  printf("ipc = %p %p\n", ipc, PREVOP(ipc,Osbpp));
   pe = PREVOP(ipc,Osbpp)->u.Osbpp.p0;
   return UnifyPredInfo(pe, 2 PASS_REGS) &&
     Yap_unify(ARG5,MkIntegerTerm(ClauseId(ipc,pe)));
diff --git a/C/exec.c b/C/exec.c
index 9c2a16a7f..c8b0458ff 100644
--- a/C/exec.c
+++ b/C/exec.c
@@ -165,8 +165,8 @@ do_execute(Term t, Term mod USES_REGS)
   if (PRED_GOAL_EXPANSION_ALL) {
     LOCK(LOCAL_SignalLock);
     /* disable creeping when we do goal expansion */
-    if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL && !LOCAL_InterruptsDisabled) {
-      LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;
+    if (LOCAL_ActiveSignals & (YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL) && !LOCAL_InterruptsDisabled) {
+      LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
       CreepFlag = CalculateStackGap();
     }
     UNLOCK(LOCAL_SignalLock);
@@ -337,8 +337,8 @@ do_execute_n(Term t, Term mod, unsigned int n USES_REGS)
   if (PRED_GOAL_EXPANSION_ALL) {
     LOCK(LOCAL_SignalLock);
     /* disable creeping when we do goal expansion */
-    if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL && !LOCAL_InterruptsDisabled) {
-      LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;
+    if (LOCAL_ActiveSignals & (YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL) && !LOCAL_InterruptsDisabled) {
+      LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
       CreepFlag = CalculateStackGap();
     }
     UNLOCK(LOCAL_SignalLock);
@@ -391,12 +391,16 @@ EnterCreepMode(Term t, Term mod USES_REGS) {
       return do_execute(ARG1, mod PASS_REGS);
     }
   }
-  PP = PredMetaCall;
   PredCreep = RepPredProp(PredPropByFunc(FunctorCreep,1));
-  if (mod) {
-    ARG1 = MkPairTerm(mod,t);
+  PP = PredCreep;
+  if (!IsVarTerm(t) && IsApplTerm(t) && FunctorOfTerm(t) == FunctorModule) {
+    ARG1 = MkPairTerm(ArgOfTerm(1,t),ArgOfTerm(2,t));
   } else {
-    ARG1 = MkPairTerm(TermProlog,t);
+    if (mod) {
+      ARG1 = MkPairTerm(mod,t);
+    } else {
+      ARG1 = MkPairTerm(TermProlog,t);
+    }
   }
   LOCK(LOCAL_SignalLock);
   CreepFlag = CalculateStackGap();
@@ -635,7 +639,8 @@ p_execute_clause( USES_REGS1 )
   } else {
     code = Yap_ClauseFromTerm(clt)->ClCode;
   }
-  if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
+  if (LOCAL_ActiveSignals & (YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL)) {
+    LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
     Yap_signal(YAP_CREEP_SIGNAL);
   }
   return CallPredicate(RepPredProp(pe), cut_cp, code PASS_REGS);
@@ -650,7 +655,7 @@ p_execute_in_mod( USES_REGS1 )
 static Int
 p_do_goal_expansion( USES_REGS1 )
 {
-  Int creeping = LOCAL_ActiveSignals & YAP_CREEP_SIGNAL;
+  Int creeping = LOCAL_ActiveSignals & (YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
   Int out = FALSE;
   PredEntry *pe;
   Term cmod = Deref(ARG2);
@@ -658,7 +663,7 @@ p_do_goal_expansion( USES_REGS1 )
   ARG2 = ARG3;
   /* disable creeping */
   LOCK(LOCAL_SignalLock);
-  LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;    
+  LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);    
   if (!LOCAL_ActiveSignals)
     CreepFlag = CalculateStackGap();
   UNLOCK(LOCAL_SignalLock);
@@ -713,14 +718,14 @@ p_do_goal_expansion( USES_REGS1 )
 static Int
 p_do_term_expansion( USES_REGS1 )
 {
-  Int creeping = LOCAL_ActiveSignals & YAP_CREEP_SIGNAL;
+  Int creeping = LOCAL_ActiveSignals & (YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
   Int out = FALSE;
   PredEntry *pe;
   Term cmod = CurrentModule;
 
   /* disable creeping */
   LOCK(LOCAL_SignalLock);
-  LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;    
+  LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
   if (!LOCAL_ActiveSignals)
     CreepFlag = CalculateStackGap();
   UNLOCK(LOCAL_SignalLock);
@@ -896,7 +901,8 @@ p_execute_nonstop( USES_REGS1 )
   /*	N = arity; */
   /* call may not define new system predicates!! */
   if (RepPredProp(pe)->PredFlags & SpiedPredFlag) {
-    if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL  && !LOCAL_InterruptsDisabled) {
+    if (LOCAL_ActiveSignals & (YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL)  && !LOCAL_InterruptsDisabled) {
+      LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
       Yap_signal(YAP_CREEP_SIGNAL);
     }
 #if defined(YAPOR) || defined(THREADS)
@@ -1771,12 +1777,9 @@ Yap_InitYaamRegs( int myworker_id )
 #endif /* FROZEN_STACKS */
   LOCK(REMOTE_SignalLock(myworker_id));
   CreepFlag = CalculateStackGap();
-  UNLOCK(REMOTE_SignalLock(myworker_id));
-  Yap_PrepGoal(0, NULL, NULL PASS_REGS);
   /* the first real choice-point will also have AP=FAIL */ 
   /* always have an empty slots for people to use */
   CurSlot = 0;
-  Yap_StartSlots( PASS_REGS1 );
   REMOTE_GlobalArena(myworker_id) = TermNil;
   h0var = MkVarTerm();
 #if defined(YAPOR) || defined(THREADS)
@@ -1802,11 +1805,14 @@ Yap_InitYaamRegs( int myworker_id )
 #if defined MYDDAS_MYSQL || defined MYDDAS_ODBC
   Yap_REGS.MYDDAS_GLOBAL_POINTER = NULL;
 #endif
+  Yap_PrepGoal(0, NULL, NULL PASS_REGS);
+  Yap_StartSlots( PASS_REGS1 );
 #ifdef TABLING
   /* ensure that LOCAL_top_dep_fr is always valid */
   if (REMOTE_top_dep_fr(myworker_id))
     DepFr_cons_cp(REMOTE_top_dep_fr(myworker_id)) = NORM_CP(B);
 #endif
+  UNLOCK(REMOTE_SignalLock(myworker_id));
 }
 
 static Int
@@ -1817,41 +1823,6 @@ p_uncaught_throw( USES_REGS1 )
   return out;
 }
 
-static Int
-p_creep_allowed( USES_REGS1 )
-{
-  if (PP != NULL) {
-    LOCK(LOCAL_SignalLock);
-    if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL  && !LOCAL_InterruptsDisabled) {
-      LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;    
-      if (!LOCAL_ActiveSignals)
-	CreepFlag = CalculateStackGap();
-      UNLOCK(LOCAL_SignalLock);
-    } else {
-      UNLOCK(LOCAL_SignalLock);
-    }
-    return TRUE;
-  }
-  return FALSE;
-}
-
-static Int
-p_debug_on( USES_REGS1 )
-{
-  Term t = Deref(ARG1);
-  if (IsVarTerm(t)) {
-    if (LOCAL_DebugOn)
-      return Yap_unify(MkAtomTerm(AtomTrue),ARG1);
-    else
-      return Yap_unify(MkAtomTerm(AtomFalse),ARG1);
-  }
-  if (t == MkAtomTerm(AtomTrue))
-    LOCAL_DebugOn = TRUE;
-  else
-    LOCAL_DebugOn = FALSE;
-  return TRUE;
-}
-
 Term 
 Yap_GetException(void)
 {
@@ -1939,7 +1910,6 @@ Yap_InitExecFs(void)
   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, 0);
 #endif
@@ -1959,7 +1929,6 @@ Yap_InitExecFs(void)
   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, 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);
diff --git a/C/signals.c b/C/signals.c
new file mode 100644
index 000000000..0a6aea138
--- /dev/null
+++ b/C/signals.c
@@ -0,0 +1,381 @@
+/*************************************************************************
+*									 *
+*	 YAP Prolog 							 *
+*									 *
+*	Yap Prolog was developed at NCCUP - Universidade do Porto	 *
+*									 *
+* Copyright L.Damas, V. Santos Costa and Universidade do Porto 1985--	 *
+*									 *
+**************************************************************************
+*									 *
+* File:		signal.c						 *
+* comments:	Signal Handling & Debugger Support			 *
+*									 *
+*									 *
+*									 *
+*************************************************************************/
+#ifdef SCCS
+static char     SccsId[] = "%W% %G%";
+#endif
+
+#define HAS_CACHE_REGS 1
+
+#include "Yap.h"
+#include "Yatom.h"
+#include "YapHeap.h"
+#include "eval.h"
+#include "yapio.h"
+#ifdef TABLING
+#include "tab.macros.h"
+#endif /* TABLING */
+#include <stdio.h>
+#if HAVE_STRING_H
+#include <string.h>
+#endif
+#if HAVE_MALLOC_H
+#include <malloc.h>
+#endif
+#include <wchar.h>
+
+inline static void
+do_signal(yap_signals sig USES_REGS)
+{
+  LOCK(LOCAL_SignalLock);
+  if (!LOCAL_InterruptsDisabled)
+    CreepFlag = Unsigned(LCL0);
+  LOCAL_ActiveSignals |= sig;
+  UNLOCK(LOCAL_SignalLock);
+}
+
+inline static void
+undo_signal(yap_signals sig USES_REGS)
+{
+  LOCK(LOCAL_SignalLock);
+  if ((LOCAL_ActiveSignals & ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL)) == sig) {
+    CreepFlag = CalculateStackGap();
+  }
+  LOCAL_ActiveSignals &= ~sig;
+  UNLOCK(LOCAL_SignalLock);
+}
+
+static Int 
+p_creep( USES_REGS1 )
+{
+  Atom            at;
+  PredEntry      *pred;
+
+  at = AtomCreep;
+  pred = RepPredProp(PredPropByFunc(Yap_MkFunctor(at, 1),0));
+  CreepCode = pred;
+  do_signal(YAP_CREEP_SIGNAL PASS_REGS);
+  return TRUE;
+}
+
+static Int 
+p_stop_creeping( USES_REGS1 )
+{
+  Atom            at;
+  PredEntry      *pred;
+
+  LOCK(LOCAL_SignalLock);
+  LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
+  if (!LOCAL_ActiveSignals) {
+    CreepFlag = CalculateStackGap();
+  }
+  UNLOCK(LOCAL_SignalLock);
+  return TRUE;
+}
+
+static Int 
+p_meta_creep( USES_REGS1 )
+{
+  Atom            at;
+  PredEntry      *pred;
+
+  at = AtomCreep;
+  pred = RepPredProp(PredPropByFunc(Yap_MkFunctor(at, 1),0));
+  CreepCode = pred;
+  LOCK(LOCAL_SignalLock);
+  LOCAL_ActiveSignals |= YAP_DELAY_CREEP_SIGNAL;
+  UNLOCK(LOCAL_SignalLock);
+  return TRUE;
+}
+
+static Int
+p_creep_allowed( USES_REGS1 )
+{
+  if (PP != NULL) {
+    LOCK(LOCAL_SignalLock);
+    if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL  && !LOCAL_InterruptsDisabled) {
+      LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;    
+      if (!LOCAL_ActiveSignals)
+	CreepFlag = CalculateStackGap();
+      UNLOCK(LOCAL_SignalLock);
+    } else {
+      UNLOCK(LOCAL_SignalLock);
+    }
+    return TRUE;
+  }
+  return FALSE;
+}
+
+static Int
+p_debug_on( USES_REGS1 )
+{
+  Term t = Deref(ARG1);
+  if (IsVarTerm(t)) {
+    if (LOCAL_DebugOn)
+      return Yap_unify(MkAtomTerm(AtomTrue),ARG1);
+    else
+      return Yap_unify(MkAtomTerm(AtomFalse),ARG1);
+  }
+  if (t == MkAtomTerm(AtomTrue))
+    LOCAL_DebugOn = TRUE;
+  else
+    LOCAL_DebugOn = FALSE;
+  return TRUE;
+}
+
+
+void 
+Yap_signal(yap_signals sig)
+{
+  CACHE_REGS
+  do_signal(sig PASS_REGS);
+}
+
+void 
+Yap_undo_signal(yap_signals sig)
+{
+  CACHE_REGS
+  undo_signal(sig PASS_REGS);
+}
+
+#ifdef DEBUG
+static Int 
+p_debug( USES_REGS1 )
+{				/* $debug(+Flag) */
+  int             i = IntOfTerm(Deref(ARG1));
+
+  if (i >= 'a' && i <= 'z')
+    GLOBAL_Option[i - 96] = !GLOBAL_Option[i - 96];
+  return (1);
+}
+#endif
+
+static Int
+p_first_signal( USES_REGS1 )
+{
+  LOCK(LOCAL_SignalLock);
+#ifdef THREADS
+  pthread_mutex_lock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+  /* always do wakeups first, because you don't want to keep the
+     non-backtrackable variable bad */
+  if (LOCAL_ActiveSignals & YAP_WAKEUP_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_WAKEUP_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigWakeUp));
+  }
+  if (LOCAL_ActiveSignals & YAP_ITI_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_ITI_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigIti));
+  }
+  if (LOCAL_ActiveSignals & YAP_INT_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_INT_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigInt));
+  }
+  if (LOCAL_ActiveSignals & YAP_USR2_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_USR2_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigUsr2));
+  }
+  if (LOCAL_ActiveSignals & YAP_USR1_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_USR1_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigUsr1));
+  }
+  if (LOCAL_ActiveSignals & YAP_PIPE_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_PIPE_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigPipe));
+  }
+  if (LOCAL_ActiveSignals & YAP_HUP_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_HUP_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigHup));
+  }
+  if (LOCAL_ActiveSignals & YAP_ALARM_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_ALARM_SIGNAL;
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigAlarm));
+  }
+  if (LOCAL_ActiveSignals & YAP_VTALARM_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_VTALARM_SIGNAL;
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigVTAlarm));
+  }
+  if (LOCAL_ActiveSignals & YAP_DELAY_CREEP_SIGNAL) {
+    LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigDelayCreep));
+  }
+  if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigCreep));
+  }
+  if (LOCAL_ActiveSignals & YAP_TRACE_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_TRACE_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigTrace));
+  }
+  if (LOCAL_ActiveSignals & YAP_DEBUG_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_DEBUG_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigDebug));
+  }
+  if (LOCAL_ActiveSignals & YAP_BREAK_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_BREAK_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigBreak));
+  }
+  if (LOCAL_ActiveSignals & YAP_STACK_DUMP_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_STACK_DUMP_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigStackDump));
+  }
+  if (LOCAL_ActiveSignals & YAP_STATISTICS_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_STATISTICS_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomSigStatistics));
+  }
+  if (LOCAL_ActiveSignals & YAP_FAIL_SIGNAL) {
+    LOCAL_ActiveSignals &= ~YAP_FAIL_SIGNAL;
+#ifdef THREADS
+    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+    UNLOCK(LOCAL_SignalLock);
+    return Yap_unify(ARG1, MkAtomTerm(AtomFail));
+  }
+#ifdef THREADS
+  pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+  UNLOCK(LOCAL_SignalLock);
+  return FALSE;
+}
+
+static Int
+p_continue_signals( USES_REGS1 )
+{
+  /* hack to force the signal anew */
+  if (LOCAL_ActiveSignals & YAP_ITI_SIGNAL) {
+    Yap_signal(YAP_ITI_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_INT_SIGNAL) {
+    Yap_signal(YAP_INT_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_USR2_SIGNAL) {
+    Yap_signal(YAP_USR2_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_USR1_SIGNAL) {
+    Yap_signal(YAP_USR1_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_HUP_SIGNAL) {
+    Yap_signal(YAP_HUP_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_ALARM_SIGNAL) {
+    Yap_signal(YAP_ALARM_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_VTALARM_SIGNAL) {
+    Yap_signal(YAP_VTALARM_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
+    Yap_signal(YAP_CREEP_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_DELAY_CREEP_SIGNAL) {
+    Yap_signal(YAP_DELAY_CREEP_SIGNAL|YAP_CREEP_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_TRACE_SIGNAL) {
+    Yap_signal(YAP_TRACE_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_DEBUG_SIGNAL) {
+    Yap_signal(YAP_DEBUG_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_BREAK_SIGNAL) {
+    Yap_signal(YAP_BREAK_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_STACK_DUMP_SIGNAL) {
+    Yap_signal(YAP_STACK_DUMP_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_STATISTICS_SIGNAL) {
+    Yap_signal(YAP_STATISTICS_SIGNAL);
+  }
+  if (LOCAL_ActiveSignals & YAP_FAIL_SIGNAL) {
+    Yap_signal(YAP_FAIL_SIGNAL);
+  }
+#ifdef THREADS
+  pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
+#endif  
+  return TRUE;
+}
+
+void
+Yap_InitSignalCPreds(void)
+{
+  /* Basic predicates for the debugger */
+  Yap_InitCPred("$creep", 0, p_creep, SafePredFlag);
+  Yap_InitCPred("$meta_creep", 0, p_meta_creep, SafePredFlag);
+  Yap_InitCPred("$stop_creeping", 0, p_stop_creeping, SafePredFlag);
+  Yap_InitCPred ("$first_signal", 1, p_first_signal, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred ("$continue_signals", 0, p_continue_signals, SafePredFlag|SyncPredFlag);
+  Yap_InitCPred("$debug_on", 1, p_debug_on, 0);
+  Yap_InitCPred("$creep_allowed", 0, p_creep_allowed, 0);
+#ifdef DEBUG
+  Yap_InitCPred("$debug", 1, p_debug, SafePredFlag|SyncPredFlag);
+#endif
+}
diff --git a/C/stdpreds.c b/C/stdpreds.c
index 8345ab901..eaeb66e2d 100644
--- a/C/stdpreds.c
+++ b/C/stdpreds.c
@@ -474,207 +474,6 @@ p_values( USES_REGS1 )
   return (TRUE);
 }
 
-inline static void
-do_signal(yap_signals sig USES_REGS)
-{
-  LOCK(LOCAL_SignalLock);
-  if (!LOCAL_InterruptsDisabled)
-    CreepFlag = Unsigned(LCL0);
-  LOCAL_ActiveSignals |= sig;
-  UNLOCK(LOCAL_SignalLock);
-}
-
-inline static void
-undo_signal(yap_signals sig USES_REGS)
-{
-  LOCK(LOCAL_SignalLock);
-  if (LOCAL_ActiveSignals == sig) {
-    CreepFlag = CalculateStackGap();
-  }
-  LOCAL_ActiveSignals &= ~sig;
-  UNLOCK(LOCAL_SignalLock);
-}
-
-
-static Int 
-p_creep( USES_REGS1 )
-{
-  Atom            at;
-  PredEntry      *pred;
-
-  at = AtomCreep;
-  pred = RepPredProp(PredPropByFunc(Yap_MkFunctor(at, 1),0));
-  CreepCode = pred;
-  do_signal(YAP_CREEP_SIGNAL PASS_REGS);
-  return TRUE;
-}
-
-static Int 
-p_signal_creep( USES_REGS1 )
-{
-  Atom            at;
-  PredEntry      *pred;
-
-  at = AtomCreep;
-  pred = RepPredProp(PredPropByFunc(Yap_MkFunctor(at, 1),0));
-  CreepCode = pred;
-  LOCK(LOCAL_SignalLock);
-  LOCAL_ActiveSignals |= YAP_CREEP_SIGNAL;
-  UNLOCK(LOCAL_SignalLock);
-  return TRUE;
-}
-
-static Int 
-p_disable_creep( USES_REGS1 )
-{
-  LOCK(LOCAL_SignalLock);
-  if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;    
-    if (!LOCAL_ActiveSignals)
-      CreepFlag = CalculateStackGap();
-    UNLOCK(LOCAL_SignalLock);
-    return TRUE;
-  }
-  UNLOCK(LOCAL_SignalLock);
-  return FALSE;
-}
-
-/* never fails */
-static Int 
-p_disable_docreep( USES_REGS1 )
-{
-  LOCK(LOCAL_SignalLock);
-  if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;    
-    if (!LOCAL_ActiveSignals)
-      CreepFlag = CalculateStackGap();
-    UNLOCK(LOCAL_SignalLock);
-  } else {
-    UNLOCK(LOCAL_SignalLock);
-  }
-  return TRUE;
-}
-
-static Int 
-p_stop_creep( USES_REGS1 )
-{
-  LOCK(LOCAL_SignalLock);
-  LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;
-  if (!LOCAL_ActiveSignals) {
-    CreepFlag = CalculateStackGap();
-  }
-  UNLOCK(LOCAL_SignalLock);
-  return TRUE;
-}
-
-void 
-Yap_signal(yap_signals sig)
-{
-  CACHE_REGS
-  do_signal(sig PASS_REGS);
-}
-
-void 
-Yap_undo_signal(yap_signals sig)
-{
-  CACHE_REGS
-  undo_signal(sig PASS_REGS);
-}
-
-#ifdef undefined
-
-/*
- * Returns where some particular piece of code is, it may take its time but
- * then you only need it while creeping, so why bother ? 
- */
-static CODEADDR *
-FindAtom(codeToFind, arity)
-     CODEADDR        codeToFind;
-     unsigned int   *arityp;
-{
-  Atom            a;
-  int             i;
-
-  for (i = 0; i < AtomHashTableSize; ++i) {
-    READ_LOCK(HashChain[i].AeRWLock);
-    a = HashChain[i].Entry;
-    READ_UNLOCK(HashChain[i].AeRWLock);
-    while (a != NIL) {
-      register PredEntry *pp;
-      AtomEntry *ae = RepAtom(a);
-      READ_LOCK(ae->ARWLock);
-      pp = RepPredProp(RepAtom(a)->PropsOfAE);
-      while (!EndOfPAEntr(pp) && ((pp->KindOfPE & 0x8000)
-				  || (pp->CodeOfPred != codeToFind)))
-	pp = RepPredProp(pp->NextOfPE);
-      if (pp != NIL) {
-	CODEADDR *out;
-	PELOCK(90,pp);
-	out = &(pp->CodeOfPred)
-	*arityp = pp->ArityOfPE;
-	UNLOCK(pp->PELock);
-	READ_UNLOCK(ae->ARWLock);
-	return (out);
-      }
-      a = RepAtom(a)->NextOfAE;
-      READ_UNLOCK(ae->ARWLock);
-    }
-  }
-  for (i = 0; i < WideAtomHashTableSize; ++i) {
-    READ_LOCK(HashChain[i].AeRWLock);
-    a = HashChain[i].Entry;
-    READ_UNLOCK(HashChain[i].AeRWLock);
-    while (a != NIL) {
-      register PredEntry *pp;
-      AtomEntry *ae = RepAtom(a);
-      READ_LOCK(ae->ARWLock);
-      pp = RepPredProp(RepAtom(a)->PropsOfAE);
-      while (!EndOfPAEntr(pp) && ((pp->KindOfPE & 0x8000)
-				  || (pp->CodeOfPred != codeToFind)))
-	pp = RepPredProp(pp->NextOfPE);
-      if (pp != NIL) {
-	CODEADDR *out;
-	PELOCK(91,pp);
-	out = &(pp->CodeOfPred)
-	*arityp = pp->ArityOfPE;
-	UNLOCK(pp->PELock);
-	READ_UNLOCK(ae->ARWLock);
-	return (out);
-      }
-      a = RepAtom(a)->NextOfAE;
-      READ_UNLOCK(ae->ARWLock);
-    }
-  }
-  *arityp = 0;
-  return (0);
-}
-
-/*
- * This is called when you want to creep a C-predicate or a predicate written
- * in assembly 
- */
-CELL 
-FindWhatCreep(toCreep)
-     CELL            toCreep;
-{
-  unsigned int    arity;
-  Atom            at;
-  CODEADDR       *place;
-
-  if (toCreep > 64) {	/* written in C */
-    int             i;
-    place = FindAtom((CODEADDR) toCreep, &arity);
-    *--ASP = Unsigned(P);
-    *--ASP = N = arity;
-    for (i = 1; i <= arity; ++i)
-      *--ASP = X[i];
-    /* P = CellPtr(CCREEPCODE);		 */
-    return (Unsigned(place));
-  }
-}
-
-#endif				/* undefined */
-
 static Int 
 p_opdec( USES_REGS1 )
 {				/* '$opdec'(p,type,atom)		 */
@@ -3466,18 +3265,6 @@ init_current_atom_op( USES_REGS1 )
   return cont_current_atom_op( PASS_REGS1 );
 }
 
-#ifdef DEBUG
-static Int 
-p_debug( USES_REGS1 )
-{				/* $debug(+Flag) */
-  int             i = IntOfTerm(Deref(ARG1));
-
-  if (i >= 'a' && i <= 'z')
-    GLOBAL_Option[i - 96] = !GLOBAL_Option[i - 96];
-  return (1);
-}
-#endif
-
 static Int 
 p_flags( USES_REGS1 )
 {				/* $flags(+Functor,+Mod,?OldFlags,?NewFlags) */
@@ -4441,17 +4228,6 @@ Yap_InitCPreds(void)
   Yap_InitCPred("$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("$creep", 0, p_creep, SafePredFlag);
-  Yap_InitCPred("$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);
-#endif
   /* Accessing and changing the flags for a predicate */
   Yap_InitCPred("$flags", 4, p_flags, SyncPredFlag);
   /* hiding and unhiding some predicates */
@@ -4510,6 +4286,7 @@ Yap_InitCPreds(void)
 #endif
   Yap_udi_init();
 
+  Yap_InitSignalCPreds();
   Yap_InitUserCPreds();
   Yap_InitUtilCPreds();
   Yap_InitSortPreds();
diff --git a/C/sysbits.c b/C/sysbits.c
index 4725607c6..9e26c9add 100755
--- a/C/sysbits.c
+++ b/C/sysbits.c
@@ -2804,207 +2804,6 @@ Yap_ReInitWallTime (void)
   InitLastWtime();
 }
 
-static Int
-p_first_signal( USES_REGS1 )
-{
-  LOCK(LOCAL_SignalLock);
-#ifdef THREADS
-  pthread_mutex_lock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-  /* always do wakeups first, because you don't want to keep the
-     non-backtrackable variable bad */
-  if (LOCAL_ActiveSignals & YAP_WAKEUP_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_WAKEUP_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigWakeUp));
-  }
-  if (LOCAL_ActiveSignals & YAP_ITI_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_ITI_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigIti));
-  }
-  if (LOCAL_ActiveSignals & YAP_INT_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_INT_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigInt));
-  }
-  if (LOCAL_ActiveSignals & YAP_USR2_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_USR2_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigUsr2));
-  }
-  if (LOCAL_ActiveSignals & YAP_USR1_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_USR1_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigUsr1));
-  }
-  if (LOCAL_ActiveSignals & YAP_PIPE_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_PIPE_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigPipe));
-  }
-  if (LOCAL_ActiveSignals & YAP_HUP_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_HUP_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigHup));
-  }
-  if (LOCAL_ActiveSignals & YAP_ALARM_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_ALARM_SIGNAL;
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigAlarm));
-  }
-  if (LOCAL_ActiveSignals & YAP_VTALARM_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_VTALARM_SIGNAL;
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigVTAlarm));
-  }
-  if (LOCAL_ActiveSignals & YAP_DELAY_CREEP_SIGNAL) {
-    LOCAL_ActiveSignals &= ~(YAP_CREEP_SIGNAL|YAP_DELAY_CREEP_SIGNAL);
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigDelayCreep));
-  }
-  if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_CREEP_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigCreep));
-  }
-  if (LOCAL_ActiveSignals & YAP_TRACE_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_TRACE_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigTrace));
-  }
-  if (LOCAL_ActiveSignals & YAP_DEBUG_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_DEBUG_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigDebug));
-  }
-  if (LOCAL_ActiveSignals & YAP_BREAK_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_BREAK_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigBreak));
-  }
-  if (LOCAL_ActiveSignals & YAP_STACK_DUMP_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_STACK_DUMP_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigStackDump));
-  }
-  if (LOCAL_ActiveSignals & YAP_STATISTICS_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_STATISTICS_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomSigStatistics));
-  }
-  if (LOCAL_ActiveSignals & YAP_FAIL_SIGNAL) {
-    LOCAL_ActiveSignals &= ~YAP_FAIL_SIGNAL;
-#ifdef THREADS
-    pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-    UNLOCK(LOCAL_SignalLock);
-    return Yap_unify(ARG1, MkAtomTerm(AtomFail));
-  }
-#ifdef THREADS
-  pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-  UNLOCK(LOCAL_SignalLock);
-  return FALSE;
-}
-
-static Int
-p_continue_signals( USES_REGS1 )
-{
-  /* hack to force the signal anew */
-  if (LOCAL_ActiveSignals & YAP_ITI_SIGNAL) {
-    Yap_signal(YAP_ITI_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_INT_SIGNAL) {
-    Yap_signal(YAP_INT_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_USR2_SIGNAL) {
-    Yap_signal(YAP_USR2_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_USR1_SIGNAL) {
-    Yap_signal(YAP_USR1_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_HUP_SIGNAL) {
-    Yap_signal(YAP_HUP_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_ALARM_SIGNAL) {
-    Yap_signal(YAP_ALARM_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_VTALARM_SIGNAL) {
-    Yap_signal(YAP_VTALARM_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_CREEP_SIGNAL) {
-    Yap_signal(YAP_CREEP_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_DELAY_CREEP_SIGNAL) {
-    Yap_signal(YAP_DELAY_CREEP_SIGNAL|YAP_CREEP_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_TRACE_SIGNAL) {
-    Yap_signal(YAP_TRACE_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_DEBUG_SIGNAL) {
-    Yap_signal(YAP_DEBUG_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_BREAK_SIGNAL) {
-    Yap_signal(YAP_BREAK_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_STACK_DUMP_SIGNAL) {
-    Yap_signal(YAP_STACK_DUMP_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_STATISTICS_SIGNAL) {
-    Yap_signal(YAP_STATISTICS_SIGNAL);
-  }
-  if (LOCAL_ActiveSignals & YAP_FAIL_SIGNAL) {
-    Yap_signal(YAP_FAIL_SIGNAL);
-  }
-#ifdef THREADS
-  pthread_mutex_unlock(&(LOCAL_ThreadHandle.tlock));
-#endif  
-  return TRUE;
-}
-
 static Int
 p_unix( USES_REGS1 )
 {
@@ -3295,9 +3094,7 @@ Yap_InitSysPreds(void)
   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);
diff --git a/H/Yapproto.h b/H/Yapproto.h
index a132d015a..3e273c7f7 100644
--- a/H/Yapproto.h
+++ b/H/Yapproto.h
@@ -338,6 +338,11 @@ void	STD_PROTO(Yap_InitSavePreds,(void));
 
 /* scanner.c */
 
+/* signals.c */
+void	STD_PROTO(Yap_signal,(yap_signals));
+void	STD_PROTO(Yap_undo_signal,(yap_signals));
+void	STD_PROTO(Yap_InitSignalPreds,(void));
+
 /* sort.c */
 void    STD_PROTO(Yap_InitSortPreds,(void));
 
@@ -345,8 +350,6 @@ void    STD_PROTO(Yap_InitSortPreds,(void));
 void	STD_PROTO(Yap_InitBackCPreds,(void));
 void	STD_PROTO(Yap_InitCPreds,(void));
 void	STD_PROTO(Yap_show_statistics,(void));
-void	STD_PROTO(Yap_signal,(yap_signals));
-void	STD_PROTO(Yap_undo_signal,(yap_signals));
 int	STD_PROTO(Yap_IsOpMaxPrio,(Atom));
 
 /* sysbits.c */
diff --git a/pl/attributes.yap b/pl/attributes.yap
index 89ad495b3..84078cac4 100644
--- a/pl/attributes.yap
+++ b/pl/attributes.yap
@@ -216,14 +216,14 @@ attvar_residuals(att(Module,Value,As), V) -->
 	       ->
 	      []
 	      ;
-	      { '$notrace'(Module:attribute_goal(V, Goal)) },
+	      { call(Module:attribute_goal(V, Goal)) },
 	      dot_list(Goal)
 	    )
 	;   (	{ current_predicate(Module:attribute_goals/3) }
-	    ->	{ '$notrace'(Module:attribute_goals(V, Goals, [])) },
+	    ->	{ call(Module:attribute_goals(V, Goals, [])) },
 		list(Goals)
 	    ;	{ current_predicate(Module:attribute_goal/2) }
-	    ->	{ '$notrace'(Module:attribute_goal(V, Goal)) },
+	    ->	{ call(Module:attribute_goal(V, Goal)) },
 		dot_list(Goal)
 	    ;	[put_attr(V, Module, Value)]
 	    ),
@@ -312,7 +312,7 @@ pick_att_vars([_|L],NL) :-
 project_module([], _, _).
 project_module([Mod|LMods], LIV, LAV) :-
 	'$pred_exists'(project_attributes(LIV, LAV),Mod),
-	'$notrace'(Mod:project_attributes(LIV, LAV)), !,
+	call(Mod:project_attributes(LIV, LAV)), !,
 	attributes:all_attvars(NLAV),
 	project_module(LMods,LIV,NLAV).
 project_module([_|LMods], LIV, LAV) :-
diff --git a/pl/boot.yap b/pl/boot.yap
index 3c1ddd51a..410069815 100755
--- a/pl/boot.yap
+++ b/pl/boot.yap
@@ -220,7 +220,6 @@ true :- true.
 	'$run_atom_goal'(GA),
 	( '$pred_exists'(halt(_), user) -> halt(0) ; '$halt'(0) ).
 '$enter_top_level' :-
-	'$disable_docreep',
 	'$run_toplevel_hooks',
 	prompt1(' ?- '),
 	'$read_toplevel'(Command,Varnames),
@@ -378,9 +377,7 @@ true :- true.
  % but YAP and SICStus does.
  %
  '$process_directive'(G, _, M, VL, Pos) :-
-	 '$exit_system_mode',
-	 ( '$notrace'(M:G) -> true ; format(user_error,':- ~w:~w failed.~n',[M,G]) ),
-	 '$enter_system_mode'.
+	 ( '$execute'(M:G) -> true ; format(user_error,':- ~w:~w failed.~n',[M,G]) ).
 
  '$continue_with_command'(Where,V,'$stream_position'(C,_P,A1,A2,A3),'$source_location'(_F,L):G,Source) :- !,
 	  '$continue_with_command'(Where,V,'$stream_position'(C,L,A1,A2,A3),G,Source).
@@ -489,10 +486,9 @@ true :- true.
 '$query'(G,V) :-
 	 (
 	  yap_hacks:current_choice_point(CP),
-	   '$exit_system_mode',
-	  '$execute'(G),
+	  '$current_module'(M),
+	  '$execute_outside_system_mode'(G, M),
 	  yap_hacks:current_choice_point(NCP),
-	  ( '$enter_system_mode' ; '$exit_system_mode', fail),
 	  '$delayed_goals'(G, V, NV, LGs, DCP),
 	  '$write_answer'(NV, LGs, Written),
 	  '$write_query_answer_true'(Written),
@@ -507,7 +503,6 @@ true :- true.
 	  ),
 	  fail	 
 	 ;
-	  '$enter_system_mode',
 	  '$out_neg_answer'
 	 ).
 
@@ -516,13 +511,16 @@ true :- true.
 	 '$do_yes_no'(G,M),
 	 '$delayed_goals'(G, [], NV, LGs, _),
 	 '$write_answer'(NV, LGs, Written),
-	 ( Written = [] ->
-	 !,'$present_answer'(C, yes);
-	 '$another', !
+	 (
+	  Written = []
+	 ->
+	 !,
+	  '$present_answer'(C, yes)
+	 ;
+	  '$another', !
 	 ),
 	 fail.
  '$yes_no'(_,_) :-
-	 '$enter_system_mode',
 	 '$out_neg_answer'.
 
 '$add_env_and_fail' :- fail.
@@ -552,11 +550,11 @@ true :- true.
 	 ),
 	 fail.
 
-'$do_yes_no'([X|L], M) :- !, '$csult'([X|L], M).
+'$do_yes_no'([X|L], M) :-
+	!,
+	'$csult'([X|L], M).
 '$do_yes_no'(G, M) :-
-	'$exit_system_mode',
-	'$execute'(M:G),
-	( '$enter_system_mode' ; '$exit_system_mode', fail).
+	'$execute_outside_system_mode'(G, M).
 
 '$write_query_answer_true'([]) :- !,
 	format(user_error,'~ntrue',[]).
@@ -1090,7 +1088,7 @@ bootstrap(F) :-
 % support SWI hook in a separate predicate, to avoid slow down standard consult.
 '$enter_command_with_hook'(Stream,Status) :-
 	'$read_vars'(Stream,Command,_,Pos,Vars, '|: ', Comments),
-	('$notrace'(prolog:comment_hook(Comments,Pos,Command)) -> true ; true ),
+	('$exit_system_mode'(comment_hook(Comments,Pos,Command), prolog) -> true ; true ),
 	'$command'(Command,Vars,Pos,Status).
 
 '$abort_loop'(Stream) :-
@@ -1236,47 +1234,58 @@ catch_ball(C, C).
 	'$nb_getval'('$break', 0, fail),
 	recorded('$toplevel_hooks',H,_), 
 	H \= fail, !,
-	( '$oncenotrace'(H) -> true ; true).
+	( '$exit_system_mode'(H) -> true ; true).
 '$run_toplevel_hooks'.
 
 '$enter_system_mode' :-
+	'$stop_creeping',
 	nb_setval('$system_mode',on).
 
+'$in_system_mode' :-
+	'$nb_getval'('$system_mode',on,fail).
+
+'$execute_outside_system_mode'(G,M) :-
+	CP is '$last_choice_pt',	
+	'$execute_outside_system_mode'(G,M,CP).
+
+'$execute_outside_system_mode'(V,M,_) :-
+	var(V), !,
+	call(M:G).
+'$execute_outside_system_mode'(M:G, _M, CP) :- !,
+	'$execute_outside_system_mode'(G, M, CP).
+'$execute_outside_system_mode'((G1,G2), M, CP) :- !,
+	'$execute_outside_system_mode'(G1, M, CP),
+	'$execute_outside_system_mode'(G2, M, CP).
+'$execute_outside_system_mode'((G1;G2), M, CP) :- !,
+	(
+	 '$execute_outside_system_mode'(G1, M, CP)
+	;
+	 '$execute_outside_system_mode'(G2, M, CP)
+	).
+'$execute_outside_system_mode'(G, M, CP) :-
+	nb_getval('$trace', on), !,
+	'$do_spy'(G, M, CP, no).
+'$execute_outside_system_mode'(G, M, CP) :-
+	(
+	 yap_hacks:current_choice_point(CP1),
+	 '$exit_system_mode',
+	 '$execute_nonstop'(G,M),
+	 yap_hacks:current_choice_point(CP2),
+	 (CP1 == CP2 -> ! ; ( true ; '$exit_system_mode', fail ) ),
+	 '$enter_system_mode'
+	;
+	  '$enter_system_mode',
+	  fail
+	).
+
+
 '$exit_system_mode' :-
 	nb_setval('$system_mode',off),
-	( '$nb_getval'('$trace',on,fail) -> '$creep' ; true).
-
-%
-% just prevent creeping from going on...
-%
-'$notrace'(G) :-
-	'$disable_creep', !,
-	(
-		% creep was going on...
-	 yap_hacks:current_choice_point(CP0),
-	 '$execute'(G),
-	 yap_hacks:current_choice_point(CP1),
-	 ( CP0 == CP1 ->
-	   !,
-	   '$creep'
-	 ;
-	   (
-	    '$creep'
-	   ;
-	    '$disable_docreep',
-	    fail
-	   )
-	 )
-	;
-	 '$creep',
-	 fail
-	).
-'$notrace'(G) :-
-	'$execute'(G).
+	( '$nb_getval'('$trace',on,fail) -> '$meta_creep' ; true).
 
 '$run_at_thread_start' :-
 	recorded('$thread_initialization',M:D,_),
-	'$notrace'(M:D),
+	'$exit_system_mode'(D, M),
 	fail.
 '$run_at_thread_start'.
 
diff --git a/pl/consult.yap b/pl/consult.yap
index e0364f46a..dcf78a9ae 100644
--- a/pl/consult.yap
+++ b/pl/consult.yap
@@ -394,7 +394,7 @@ initialization(G,OPT) :-
 	  '$do_error'(type_error(OPT),initialization(G,OPT))
 	).
 '$initialization'(G,now) :-
-	( '$notrace'(G) -> true ; format(user_error,':- ~w:~w failed.~n',[M,G]) ).
+	( '$exit_system_mode'(G,prolog) -> true ; format(user_error,':- ~w:~w failed.~n',[M,G]) ).
 '$initialization'(G,after_load) :-
 	'$initialization'(G).
 % ignore for now.
@@ -412,7 +412,7 @@ initialization(G,OPT) :-
 	recorded('$system_initialisation',G,R),
 	erase(R),
 	G \= '$',
-	'$notrace'(G),
+	'$exit_system_mode'(G, prolog),
 	fail.
 '$exec_initialisation_goals' :-
 	'$show_consult_level'(Level),
@@ -426,7 +426,7 @@ initialization(G,OPT) :-
         ( OldMode == on -> '$exit_system_mode' ; true ),
 	% run initialization under user control (so allow debugging this stuff).
 	(
-	  '$system_catch'('$oncenotrace'(M:G), M, Error, user:'$LoopError'(Error, top)),
+	  '$system_catch'(once(M:G), M, Error, user:'$LoopError'(Error, top)),
 	  fail
 	;
           OldMode = on,
@@ -895,7 +895,7 @@ absolute_file_name(File,Opts,TrueFileName) :-
 
 
 '$extend_path_directory'(Name, D, File, Opts, NewFile, Call) :-
-	'$notrace'(user:file_search_path(Name, Dir)),
+	user:file_search_path(Name, Dir),
 	'$extend_pathd'(Dir, D, File, Opts, NewFile, Call).
 
 '$extend_pathd'(Dir, A, File, Opts, NewFile, Call) :-
diff --git a/pl/control.yap b/pl/control.yap
index 52c1a081d..de7665ba1 100644
--- a/pl/control.yap
+++ b/pl/control.yap
@@ -289,37 +289,6 @@ version(T) :-
 	fail.
 '$set_toplevel_hook'(_).
 
-'$oncenotrace'(G) :-
-	'$disable_creep', !,
-	(
-	 '$execute'(G)
-	->
-	 '$creep'
-	;
-	 '$creep',
-	 fail
-	).	
-'$oncenotrace'(G) :-
-	'$execute'(G), !.
-
-
-'$once0'(G, M) :-
-	'$pred_exists'(G, M),
-	(
-	 '$disable_creep'
-	->
-	  (
-	   '$execute_nonstop'(G, M)
-	   ->
-	   '$creep'
-	  ;
-	   '$creep',
-	    fail
-	  )
-       ;
-	  '$execute_nonstop'(G,M)
-        ).
-
 nb_getval(GlobalVariable, Val) :-
 	'$nb_getval'(GlobalVariable, Val, Error),
 	(var(Error)
diff --git a/pl/debug.yap b/pl/debug.yap
index ffe3d36fe..3dfb6ebf4 100644
--- a/pl/debug.yap
+++ b/pl/debug.yap
@@ -123,21 +123,21 @@
 	recorded('$spy','$spy'(G,M),_), !.
 
 spy Spec :-
-	'$notrace'(prolog:debug_action_hook(spy(Spec))), !.
+	prolog:debug_action_hook(spy(Spec)), !.
 spy L :-
 	'$current_module'(M),
 	'$suspy'(L, spy, M), fail.
 spy _ :- debug.
 
 nospy Spec :-
-	'$notrace'(prolog:debug_action_hook(nospy(Spec))), !.
+	prolog:debug_action_hook(nospy(Spec)), !.
 nospy L :-
 	'$current_module'(M),
 	'$suspy'(L, nospy, M), fail.
 nospy _.
 
 nospyall :-
-	'$notrace'(prolog:debug_action_hook(nospyall)), !.
+	prolog:debug_action_hook(nospyall), !.
 nospyall :-
 	recorded('$spy','$spy'(T,M),_), functor(T,F,N), '$suspy'(F/N,nospy,M), fail.
 nospyall.
@@ -173,7 +173,7 @@ trace :-
 	nb_setval('$trace',on),
 	'$start_debugging'(on),
 	print_message(informational,debug(trace)),
-	'$creep'.
+	'$meta_creep'.
 
 notrace :-
 	nodebug.
@@ -283,17 +283,21 @@ debugging :-
 	'$debug_on'(F), F = false, !,
 	'$execute_nonstop'(G,Mod).
 '$spy'([Mod|G]) :-
-	nb_getval('$system_mode',on), !,
+	'$in_system_mode', !,
 	'$execute_nonstop'(G,Mod).
 '$spy'([Mod|G]) :-
 	CP is '$last_choice_pt',	
-	'$do_spy'(G, Mod, CP, no).
+	'$do_spy'(G, Mod, CP, spy).
 
 % last argument to do_spy says that we are at the end of a context. It
 % is required to know whether we are controlled by the debugger.
-'$do_spy'(V, M, CP, Flag) :- var(V), !, '$do_spy'(call(V), M, CP, Flag).
-'$do_spy'(!, _, CP, _) :- !, '$$cut_by'(CP).
-'$do_spy'('$cut_by'(M), _, _, _) :- !, '$$cut_by'(M).
+'$do_spy'(V, M, CP, Flag) :-
+	var(V), !,
+	'$do_spy'(call(V), M, CP, Flag).
+'$do_spy'(!, _, CP, _) :-
+	!, '$$cut_by'(CP).
+'$do_spy'('$cut_by'(M), _, _, _) :-
+	!, '$$cut_by'(M).
 '$do_spy'(true, _, _, _) :- !.
 %'$do_spy'(fail, _, _, _) :- !, fail.
 '$do_spy'(M:G, _, CP, CalledFromDebugger) :- !,
@@ -307,7 +311,7 @@ debugging :-
 	  '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
 '$do_spy'((T->A|B), M, CP, CalledFromDebugger) :- !,
-	( '$do_spy'(T, M, CP, yes) -> 	'$do_spy'(A, M, CP, yes)
+	( '$do_spy'(T, M, CP, debugger) -> 	'$do_spy'(A, M, CP, yes)
 	;
 	  '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
@@ -315,13 +319,13 @@ debugging :-
 	( '$do_spy'(T, M, CP, yes) -> '$do_spy'(A, M, CP, yes) ).
 '$do_spy'((A;B), M, CP, CalledFromDebugger) :- !,
 	(
-	  '$do_spy'(A, M, CP, yes)
+	  '$do_spy'(A, M, CP, CalledFromDebugger)
 	;
 	  '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
 '$do_spy'((A|B), M, CP, CalledFromDebugger) :- !,
 	(
-	  '$do_spy'(A, M, CP, yes)
+	  '$do_spy'(A, M, CP, CalledFromDebugger)
 	;
 	  '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
@@ -335,7 +339,7 @@ debugging :-
 	nb_setval('$spy_gn',L1),	/* and save it globaly		*/
         b_getval('$spy_glist',History),	/* get goal list		*/
 	b_setval('$spy_glist',[info(L,Module,G,_Retry,_Det,_HasFoundAnswers)|History]),	/* and update it		*/
-	'$loop_spy'(L, G, Module, CalledFromDebugger).	/* set creep on		*/
+	'$loop_spy'(L, G, Module, CalledFromDebugger).	
 
 % we are skipping, so we can just call the goal,
 % while leaving the minimal structure in place.
@@ -360,7 +364,7 @@ debugging :-
 	throw(error('$fail_spy'(GoalNumber),[])).
 '$loop_spy_event'(error('$done_spy'(G0),_), GoalNumber, G, _, CalledFromDebugger) :-
 	G0 >= GoalNumber, !,
-	'$continue_debugging'(CalledFromDebugger).
+	'$continue_debugging'(zip, CalledFromDebugger).
 '$loop_spy_event'(error('$done_spy'(GoalNumber),_), _, _, _, _) :- !,
 	throw(error('$done_spy'(GoalNumber),[])).
 '$loop_spy_event'(Event, GoalNumber, G, Module, CalledFromDebugger) :-
@@ -380,8 +384,8 @@ debugging :-
 
 % just fail here, don't really need to call debugger, the user knows what he
 % wants to do
-'$loop_fail'(_GoalNumber, _G, _Module, _CalledFromDebugger) :-
-	'$continue_debugging'(CalledFromDebugger),
+'$loop_fail'(_GoalNumber, _G, _Module, CalledFromDebugger) :-
+	'$continue_debugging'(fail, CalledFromDebugger),
 	fail.
 
 % if we are in 
@@ -400,16 +404,16 @@ debugging :-
 	    /* call port */
 	    '$enter_goal'(GoalNumber, G, Module),
 	    '$spycall'(G, Module, CalledFromDebugger, Retry),
-	    '$disable_docreep',
 	    (
 	      '$debugger_deterministic_goal'(G) ->
 	      Det=true
 	    ;
 	      Det=false
 	    ),
-	/* go execute the predicate	*/
+	    /* go execute the continuation	*/
 	    (
-	      Retry = false ->
+	       /* exit port */
+	       Retry = false,
 	       /* found an answer, so it can redo */
 	       nb_setarg(6, Info, true),
 	      '$show_trace'(exit,G,Module,GoalNumber,Det),	/* output message at exit	*/
@@ -422,26 +426,25 @@ debugging :-
 		;
 		true
 	      ),
-	      '$continue_debugging'(CalledFromDebugger)	   
-	      ;
+	      '$continue_debugging'(exit, CalledFromDebugger)	   
+	     ;
 		/* backtracking from exit				*/
 	        /* we get here when we want to redo a goal		*/
 		/* redo port */
-	     '$disable_docreep',
 	      (
-	       arg(6, Info, true)
+	         arg(6, Info, true)
 	      ->
 	        '$show_trace'(redo,G,Module,GoalNumber,_), /* inform user_error		*/
 	        nb_setarg(6, Info, false)
 	       ;
 	         true
 	      ),
-	     '$continue_debugging'(CalledFromDebugger),
+	     '$continue_debugging'(fail, CalledFromDebugger),
 	     fail			/* to backtrack to spycalls	*/
 	     )
 	  ;
 	    '$show_trace'(fail,G,Module,GoalNumber,_), /* inform at fail port		*/
-	    '$continue_debugging'(CalledFromDebugger),
+	    '$continue_debugging'(fail, CalledFromDebugger),
 	    /* fail port */
 	    fail
 	).
@@ -483,16 +486,23 @@ debugging :-
 	!,
 	'$execute_nonstop'(G,M).
 '$spycall'(G, M, _, _) :-
-        '$system_predicate'(G,M),
-	\+ '$is_metapredicate'(G,M), !,
-	'$execute'(M:G).
-'$spycall'(G, M, _, _) :-
-        '$system_module'(M), !,
-	'$execute'(M:G).
+        (
+	 '$system_predicate'(G,M)
+	;
+	 '$system_module'(M)
+	),
+	!,
+	(
+	   '$is_metapredicate'(G,M)
+	->
+	   '$meta_creep'(G,M)
+	;
+	    '$execute'(M:G)
+	).
 '$spycall'(G, M, _, _) :-
         '$tabled_predicate'(G,M),
 	 !,
-	'$continue_debugging'(no, '$execute_nonstop'(G,M)).
+	'$continue_debugging_goal'(no, '$execute_nonstop'(G,M)).
 '$spycall'(G, M, CalledFromDebugger, InRedo) :-
 	'$flags'(G,M,F,F),
 	F /\ 0x08402000 =\= 0, !, % dynamic procedure, logical semantics, or source
@@ -500,7 +510,6 @@ debugging :-
 	CP is '$last_choice_pt',
 	'$clause'(G, M, Cl, _),
 	% I may backtrack to here from far away
-	'$disable_docreep',	
 	( '$do_spy'(Cl, M, CP, CalledFromDebugger) ; InRedo = true ).
 '$spycall'(G, M, CalledFromDebugger, InRedo) :-
 	'$undefined'(G, M), !,
@@ -511,13 +520,26 @@ debugging :-
 	CP is '$last_choice_pt',
 	'$static_clause'(G,M,_,R),
 	% I may backtrack to here from far away
-	'$disable_docreep',	
 	(
-	 '$continue_debugging'(no, '$execute_clause'(G, M, R, CP))
+	 '$continue_debugging_goal'(no, '$execute_clause'(G, M, R, CP))
 	;
 	 InRedo = true
 	).
 
+'$meta_creep'(G,M) :-
+	(
+	 yap_hacks:current_choice_point(CP1),
+	 '$exit_system_mode',
+	 '$meta_creep',
+	 '$execute_nonstop'(G,M),
+	 yap_hacks:current_choice_point(CP2),
+	 (CP1 == CP2 -> ! ; ( true ; '$exit_system_mode', '$meta_creep', fail ) ),
+	 '$enter_system_mode'
+	;
+	  '$enter_system_mode',
+	  fail
+	).
+
 '$tabled_predicate'(G,M) :-
 	'$flags'(G,M,F,F),
 	F /\ 0x00000040 =\= 0.
@@ -584,8 +606,6 @@ debugging :-
 '$action'(13,P,CallNumber,G,Module,Zip) :- !,	% newline 	creep
 	get0(user_input,C),
 	'$action'(C,P,CallNumber,G,Module,Zip).
-%'$action'(10,_,_,_,_,on) :-			% newline 	creep
-%	nb_setval('$debug_jump',false).
 '$action'(10,_,_,_,_,on) :- !,			% newline 	creep
 	nb_setval('$debug_jump',false).
 '$action'(0'!,_,_,_,_,_) :- !,			% ! 'g		execute
@@ -708,20 +728,26 @@ debugging :-
 	'$ilgl'(C),
 	fail.
 
-'$continue_debugging'(yes).
+% first argument is exit, zip or fail
+% second is creep, meta_creep, spy, or debugger
+'$continue_debugging'(exit, debugger) :- !.
+'$continue_debugging'(zip, debugger) :- !.
+'$continue_debugging'(fail, debugger) :- !.
 % do not need to debug!
-'$continue_debugging'(no) :-
+'$continue_debugging'(exit, meta_creep) :- !,
+	'$meta_creep'.
+'$continue_debugging'(_, no) :-
 	'$creep'.
 
 % if we are in the interpreter, don't need to care about forcing a trace, do we?
-'$continue_debugging'(yes,G) :- !,
+'$continue_debugging_goal'(_, yes,G) :- !,
 	'$execute_dgoal'(G).
 % do not need to debug!
-'$continue_debugging'(_,G) :-
+'$continue_debugging_goal'(_, _,G) :-
 	'nb_getval'('$debug_run',Zip),
         (Zip == nodebug ;  number(Zip) ; Zip == spy ), !,
 	'$execute_dgoal'(G).
-'$continue_debugging'(_,G) :-
+'$continue_debugging_goal'(_, _,G) :-
 	'$execute_creep_dgoal'(G).
 	
 '$execute_dgoal'('$execute_nonstop'(G,M)) :-
@@ -730,10 +756,10 @@ debugging :-
 	'$execute_clause'(G, M, R, CP).
 
 '$execute_creep_dgoal'('$execute_nonstop'(G,M)) :-
-	'$signal_creep',
+	'$creep',
 	'$execute_nonstop'(G,M).
 '$execute_creep_dgoal'('$execute_clause'(G, M, R, CP)) :-
-	'$signal_creep',
+	'$creep',
 	'$execute_clause'(G, M, R, CP).
 
 '$show_ancestors'(HowMany) :-
diff --git a/pl/errors.yap b/pl/errors.yap
index 478fd425e..2a5e7c11e 100644
--- a/pl/errors.yap
+++ b/pl/errors.yap
@@ -242,13 +242,13 @@ print_message(error, error(Msg,[Info|local_sp(P,CP,Envs,CPs)])) :- !,
 	erase(R).
 print_message(Severity, Msg) :-
 	nonvar(Severity), nonvar(Msg),
-	'$notrace'(user:portray_message(Severity, Msg)), !.
+	user:portray_message(Severity, Msg), !.
 % This predicate has more hooks than a pirate ship!
 print_message(Severity, Term) :-
 	% first step at hook processing
 	'$message_to_lines'(Term, Lines),
 	(   nonvar(Term),
-	    '$once0'(message_hook(Term, Severity, Lines), user)
+	    user:message_hook(Term, Severity, Lines)
 	->
            true
 	;
@@ -263,9 +263,9 @@ print_message(_, Term) :-
 	format(user_error,'~q~n',[Term]).
 
 '$message_to_lines'(Term, Lines) :-
-	'$once0'(generate_message_hook(Term, [], Lines), user), !.
+	user:generate_message_hook(Term, [], Lines), !.
 '$message_to_lines'(Term, Lines) :-
-	'$once0'(message(Term, Lines, []), prolog), !.
+	prolog:message(Term, Lines, []), !.
 '$message_to_lines'(Term, Lines) :-
 	'$messages':generate_message(Term, Lines, []), !.
 	
diff --git a/pl/hacks.yap b/pl/hacks.yap
index c185ce79c..4ae8aef43 100644
--- a/pl/hacks.yap
+++ b/pl/hacks.yap
@@ -126,6 +126,7 @@ show_cp(CP, Continuation) -->
 show_env(Env,Cont,NCont) -->
 	{
 	 yap_hacks:continuation(Env, Addr, NCont, _),
+	format('0x~16r 0x~16r~n',[Env,NCont]),
 	 yap_hacks:cp_to_predicate(Cont, Mod, Name, Arity, ClId)
 	},
         [ '0x~16r~t  ~16+ ~d~16+ ~q:' -
diff --git a/pl/modules.yap b/pl/modules.yap
index 2f8ec6066..9cd2531dc 100644
--- a/pl/modules.yap
+++ b/pl/modules.yap
@@ -535,7 +535,7 @@ expand_goal(G, G).
 % expand argument
 '$meta_expansion_loop'(0,_,_,_,_,_,_,_) :- !.
 '$meta_expansion_loop'(I,D,G,NG,HVars,CurMod,M,HM) :- 
-	arg(I,D,X), (X==':' ; integer(X)),
+	arg(I,D,X), (X==':' -> true ; integer(X)),
 	arg(I,G,A), '$do_expand'(A,HVars),
 	!,
 	arg(I,NG,M:A),
diff --git a/pl/signals.yap b/pl/signals.yap
index 5a7e08912..ae553a988 100644
--- a/pl/signals.yap
+++ b/pl/signals.yap
@@ -33,39 +33,10 @@
 	'$wake_up_goal'(G, LG).
 % never creep on entering system mode!!!
 % don't creep on meta-call.
-'$do_signal'(sig_creep, [M|G]) :-
-	'$creep_allowed', !,
-	(
-	 ( G = '$notrace'(G0) ;  G = '$oncenotrace'(G0) ; G = '$once0'(G0) ; G = '$execute0'(G0,M) ; '$system_module'(M), G = G0 )
-	->
-	 (
-	  '$execute_nonstop'(G0,M),
-	  '$signal_creep'
-	 ;
-	  '$signal_creep',
-	  fail
-	 )
-	;
-	 '$start_creep'([M|G])
-	).
-% 
-'$do_signal'(sig_creep, [M|G]) :-
-	( G = '$notrace'(G0) ;  G = '$oncenotrace'(G0) ; G = '$once0'(G0) ; G = '$execute0'(G0,M) ; '$system_module'(M), G = G0 ),
-	!,
-	(
-	 '$execute_nonstop'(G0,M),
-	 '$signal_creep'
-	;
-	 '$signal_creep',
-	 fail
-	).
-% 
-'$do_signal'(sig_creep, [M|G]) :-
-        '$signal_creep',
-	'$execute_nonstop'(G,M).
-'$do_signal'(sig_delay_creep, [M|G]) :-
-	'$execute'(M:G),
-        '$creep'.
+'$do_signal'(sig_creep, MG) :-
+	 '$start_creep'(MG, creep).
+'$do_signal'(sig_delay_creep, MG) :-
+	 '$start_creep'(MG, meta_creep).
 '$do_signal'(sig_iti, [M|G]) :-
 	'$thread_gfetch'(Goal),
 	% if more signals alive, set creep flag
@@ -117,96 +88,12 @@
 	'$current_module'(M0),
 	'$execute0'((Goal,M:G),M0).
 
-% '$execute0' should be ignored.
-'$start_creep'([_|'$execute0'(G,M)]) :-
-	!,
-	'$start_creep'([M|G]).
-% '$call'() is a complicated thing
-'$start_creep'([M0|'$call'(G, CP, G0, M)]) :-
-	!,
-	'$creep',
-	'$execute_nonstop'('$call'(G, CP, G0, M),M0).
-% donotrace: means do not trace! So,
-% ignore and then put creep back for the continuation.
-'$start_creep'([M0|'$notrace'(G)]) :-
-	!,
-	(
-	 CP0 is '$last_choice_pt',
-	 '$execute_nonstop'(G,M0),
-	 CP1 is '$last_choice_pt',
-	 % exit port: creep
-	 '$creep',
-	 (
-	  % if deterministic just creep all you want.
-	  CP0 = CP1 ->
-	  !
-	 ;
-	  % extra disjunction protects reentry into usergoal
-	  (
-	    % cannot cut here
-	    true
-	   ;
-	    % be sure to disable creep on redo port
-	    '$disable_creep',
-	    fail
-	  )
-	 )
-	;
-	   % put it back again on fail
-	 '$creep',
-	 fail	   
-	).
-'$start_creep'([M0|'$oncenotrace'(G)]) :-
-	!,
-	('$execute_nonstop'(G,M0),
-	 CP1 is '$last_choice_pt',
-	 % exit port: creep
-	 '$creep',
-	 !
-	;
-	   % put it back again on fail
-	 '$creep',
-	 fail	   
-	).
-'$start_creep'([M0|'$once0'(G)]) :-
-	!,
-	('$execute_nonstop'(G,M0),
-	 CP1 is '$last_choice_pt',
-	 % exit port: creep
-	 '$creep',
-	 !
-	;
-	   % put it back again on fail
-	 '$creep',
-	 fail	   
-	).
-% do not debug if we are not in debug mode. 
-'$start_creep'([Mod|G]) :-
-	'$debug_on'(DBON), DBON = false, !,
-	'$execute_nonstop'(G,Mod).
-'$start_creep'([Mod|G]) :-
-	nb_getval('$system_mode',on), !,
-	'$execute_nonstop'(G,Mod).
-% notice that the last signal to be processed must always be creep
-'$start_creep'([_|'$cut_by'(CP)]) :- !,
-	'$$cut_by'(CP),
-	'$creep'.
-'$start_creep'([_|true]) :- !,
-	'$creep'.
-'$start_creep'([Mod|G]) :-
-	'$hidden_predicate'(G,Mod), !,
-	'$execute_nonstop'(G,Mod),
-	'$creep'.
-% do not debug if we are zipping through.  
-'$start_creep'([Mod|G]) :-
-	nb_getval('$debug_run',Run),
-	Run \= off,
-	'$zip'(-1, G, Mod), !,
-        '$signal_creep',
-	'$execute_goal'(G, Mod).
-'$start_creep'([Mod|G]) :-
+'$start_creep'([Mod|G], _) :-
+	'$in_system_mode', !,
+	'$execute0'(G, Mod).
+'$start_creep'([Mod|G], WhereFrom) :-
 	CP is '$last_choice_pt',	
-	'$do_spy'(G, Mod, CP, no).
+	'$do_spy'(G, Mod, CP, WhereFrom).
 
 '$execute_goal'(G, Mod) :-
 	(

From 67208c81576f1c223c4cc275676b9d8a79472b82 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADtor=20Santos=20Costa?= <vsc@dcc.fc.up.pt>
Date: Sat, 9 Feb 2013 08:51:33 -0600
Subject: [PATCH 3/4] signals

---
 Makefile.in | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index c28285ac4..afd438a20 100755
--- a/Makefile.in
+++ b/Makefile.in
@@ -257,7 +257,7 @@ C_SOURCES= \
 	$(srcdir)/C/qlyr.c \
 	$(srcdir)/C/qlyw.c \
 	$(srcdir)/C/range.c \
-	$(srcdir)/C/save.c $(srcdir)/C/scanner.c \
+	$(srcdir)/C/save.c $(srcdir)/C/scanner.c $(srcdir)/C/signals.c \
 	$(srcdir)/C/sort.c $(srcdir)/C/stdpreds.c $(srcdir)/C/sysbits.c \
 	$(srcdir)/C/threads.c \
 	$(srcdir)/C/tracer.c $(srcdir)/C/unify.c $(srcdir)/C/userpreds.c  \
@@ -366,7 +366,7 @@ ENGINE_OBJECTS = \
 	myddas_util.o myddas_statistics.o myddas_top_level.o \
 	myddas_wkb2prolog.o modules.o other.o   \
 	parser.o qlyr.o qlyw.o range.o \
-	save.o scanner.o sort.o stdpreds.o \
+	save.o scanner.o signals.o sort.o stdpreds.o \
 	sysbits.o threads.o tracer.o \
 	udi.o\
 	unify.o userpreds.o utilpreds.o \
@@ -466,6 +466,9 @@ qlyw.o: $(srcdir)/C/qlyw.c config.h
 save.o: $(srcdir)/C/save.c config.h
 	$(CC) -c $(CFLAGS) $(srcdir)/C/save.c -o $@
 
+signals.o: $(srcdir)/C/signals.c config.h
+	$(CC) -c $(CFLAGS) $(srcdir)/C/signals.c -o $@
+
 sysbits.o: $(srcdir)/C/sysbits.c config.h
 	$(CC) -c $(CFLAGS) $(srcdir)/C/sysbits.c -o $@
 

From ec7158eb997d98f38a250afb201136c0d765f5a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?V=C3=ADtor=20Santos=20Costa?= <vsc@dcc.fc.up.pt>
Date: Wed, 13 Feb 2013 09:06:06 -0600
Subject: [PATCH 4/4] debugger progress

---
 BEAM/eam_am.c   |  2 ++
 BEAM/eamamasm.h | 21 ++++++++++----------
 C/compiler.c    |  2 ++
 C/computils.c   |  3 +++
 C/exec.c        |  1 +
 C/exo.c         |  4 ++--
 C/inlines.c     | 22 +++++++++++++++++++++
 H/amidefs.h     |  1 +
 pl/boot.yap     | 45 ++++++++++++++++++++++++++----------------
 pl/control.yap  |  6 +++---
 pl/debug.yap    | 52 ++++++++++++++++++++++++++++++++++---------------
 pl/hacks.yap    |  2 +-
 pl/signals.yap  |  3 +++
 13 files changed, 115 insertions(+), 49 deletions(-)

diff --git a/BEAM/eam_am.c b/BEAM/eam_am.c
index e02dc2e40..f9c5fe187 100644
--- a/BEAM/eam_am.c
+++ b/BEAM/eam_am.c
@@ -1428,6 +1428,7 @@ static void *OpAddress[]= {
         &&p_db_ref,
         &&p_primitive,
         &&p_cut_by,
+        &&p_save_by,
         &&p_succ,
         &&p_predc,
         &&p_plus,
@@ -3536,6 +3537,7 @@ break_debug(contador);
         p_db_ref:
         p_primitive:
         p_cut_by:
+        p_save_by:
         p_succ:
         p_predc:
         p_plus:
diff --git a/BEAM/eamamasm.h b/BEAM/eamamasm.h
index c7d731cee..bbfa97a40 100644
--- a/BEAM/eamamasm.h
+++ b/BEAM/eamamasm.h
@@ -115,15 +115,16 @@
 #define _p_db_ref	(_std_base+8)
 #define _p_primitive	(_std_base+9)
 #define _p_cut_by	(_std_base+10)
-#define _p_succ		(_std_base+11)
-#define _p_predc	(_std_base+12)
-#define _p_plus		(_std_base+13)
-#define _p_minus	(_std_base+14)
-#define _p_times	(_std_base+15)
-#define _p_div		(_std_base+16)
-#define _p_dif		(_std_base+17)
-#define _p_eq		(_std_base+18)
-#define _p_arg		(_std_base+19)
-#define _p_functor	(_std_base+20)
+#define _p_save_by	(_std_base+11)
+#define _p_succ		(_std_base+12)
+#define _p_predc	(_std_base+13)
+#define _p_plus		(_std_base+14)
+#define _p_minus	(_std_base+15)
+#define _p_times	(_std_base+16)
+#define _p_div		(_std_base+17)
+#define _p_dif		(_std_base+18)
+#define _p_eq		(_std_base+19)
+#define _p_arg		(_std_base+20)
+#define _p_functor	(_std_base+21)
 
 
diff --git a/C/compiler.c b/C/compiler.c
index 9d6907a70..579d0a167 100644
--- a/C/compiler.c
+++ b/C/compiler.c
@@ -923,6 +923,8 @@ c_test(Int Op, Term t1, compiler_struct *cglobs) {
   }
   if (Op == _cut_by)
     c_var(t, commit_b_flag, 1, 0, cglobs);
+  else if (Op == _save_by)
+    c_var(t, save_b_flag, 1, 0, cglobs);
   else
     c_var(t, f_flag,(unsigned int)Op, 0, cglobs);
 }
diff --git a/C/computils.c b/C/computils.c
index 4d90d9890..c3f117195 100644
--- a/C/computils.c
+++ b/C/computils.c
@@ -331,6 +331,9 @@ bip_name(Int op, char *s)
   case _cut_by:
     strcpy(s,"cut_by");
     break;
+  case _save_by:
+    strcpy(s,"save_by");
+    break;
   case _db_ref:
     strcpy(s,"db_ref");
     break;
diff --git a/C/exec.c b/C/exec.c
index c8b0458ff..d595327c9 100644
--- a/C/exec.c
+++ b/C/exec.c
@@ -1916,6 +1916,7 @@ Yap_InitExecFs(void)
   Yap_InitCPred("$execute0", 2, p_execute0, 0);
   Yap_InitCPred("$execute_nonstop", 2, p_execute_nonstop, 0);
   Yap_InitCPred("$execute_clause", 4, p_execute_clause, 0);
+  Yap_InitCPred("$current_choice_point", 1, p_save_cp, 0);
   CurrentModule = HACKS_MODULE;
   Yap_InitCPred("current_choice_point", 1, p_save_cp, 0);
   Yap_InitCPred("current_choicepoint", 1, p_save_cp, 0);
diff --git a/C/exo.c b/C/exo.c
index c9721f568..3541a55dd 100644
--- a/C/exo.c
+++ b/C/exo.c
@@ -258,13 +258,13 @@ add_index(struct index_t **ip, UInt bmap, PredEntry *ap, UInt count, UInt bnds[]
     if (!(base = (CELL *)Yap_AllocCodeSpace(sizeof(CELL)*(ncls+i->hsize)))) {
       CACHE_REGS
       save_machine_regs();
-      LOCAL_Error_Size = 3*ncls*sizeof(CELL);
+      LOCAL_Error_Size = sizeof(CELL)*(ncls+i->hsize);
       LOCAL_ErrorMessage = "not enough space to generate indices";
       Yap_FreeCodeSpace((void *)i);
       Yap_Error(OUT_OF_HEAP_ERROR, TermNil, LOCAL_ErrorMessage);
       return NULL;
     }
-    bzero(base, 3*sizeof(CELL)*ncls);
+    bzero(base, sizeof(CELL)*(ncls+i->hsize));
   }
   i->size = sizeof(CELL)*(ncls+i->hsize)+sz+sizeof(struct index_t);
   i->key = (CELL **)base;
diff --git a/C/inlines.c b/C/inlines.c
index 59a563a46..356de33a4 100644
--- a/C/inlines.c
+++ b/C/inlines.c
@@ -760,6 +760,13 @@ p_functor( USES_REGS1 )			/* functor(?,?,?) */
   ENDD(d0);
 }
 
+static Term
+cp_as_integer(choiceptr cp USES_REGS)
+{
+  return(MkIntegerTerm(LCL0-(CELL *)cp));
+}
+
+
 static Int
 p_cut_by( USES_REGS1 )
 {
@@ -897,6 +904,20 @@ cont_genarg( USES_REGS1 )
       Yap_unify(ARG3,pt[0]);
 }
 
+static Int
+p_save_cp( USES_REGS1 )
+{
+  Term t = Deref(ARG1);
+  Term td;
+#if SHADOW_HB
+  register CELL *HBREG = HB;
+#endif
+  if (!IsVarTerm(t)) return(FALSE);
+  td = cp_as_integer(B PASS_REGS);
+  Bind((CELL *)t,td);
+  return(TRUE);
+}
+
 
 void 
 Yap_InitInlines(void)
@@ -904,6 +925,7 @@ Yap_InitInlines(void)
   CACHE_REGS
   Term cm = CurrentModule;
   Yap_InitAsmPred("$$cut_by", 1, _cut_by, p_cut_by, SafePredFlag);
+  Yap_InitAsmPred("$$save_by", 1, _save_by, p_save_cp, SafePredFlag);
   Yap_InitAsmPred("atom", 1, _atom, p_atom, SafePredFlag);
   Yap_InitAsmPred("atomic", 1, _atomic, p_atomic, SafePredFlag);
   Yap_InitAsmPred("integer", 1, _integer, p_integer, SafePredFlag);
diff --git a/H/amidefs.h b/H/amidefs.h
index cf424bc22..fbb2c224b 100644
--- a/H/amidefs.h
+++ b/H/amidefs.h
@@ -163,6 +163,7 @@ typedef enum {
   _number,
   _var,
   _cut_by,
+  _save_by,
   _db_ref,
   _primitive,
   _dif,
diff --git a/pl/boot.yap b/pl/boot.yap
index 410069815..ac477fb81 100755
--- a/pl/boot.yap
+++ b/pl/boot.yap
@@ -485,10 +485,10 @@ true :- true.
 	 '$yes_no'(G,(?-)).
 '$query'(G,V) :-
 	 (
-	  yap_hacks:current_choice_point(CP),
+	  '$current_choice_point'(CP),
 	  '$current_module'(M),
 	  '$execute_outside_system_mode'(G, M),
-	  yap_hacks:current_choice_point(NCP),
+	  '$current_choice_point'(NCP),
 	  '$delayed_goals'(G, V, NV, LGs, DCP),
 	  '$write_answer'(NV, LGs, Written),
 	  '$write_query_answer_true'(Written),
@@ -531,9 +531,9 @@ true :- true.
 '$delayed_goals'(G, V, NV, LGs, NCP) :-
 	(
 	  CP is '$last_choice_pt',
-	  yap_hacks:current_choice_point(NCP1),
+	  '$current_choice_point'(NCP1),
 	  '$attributes':delayed_goals(G, V, NV, LGs),
-	  yap_hacks:current_choice_point(NCP2),
+	  '$current_choice_point'(NCP2),
 	  '$clean_ifcp'(CP),
 	   NCP is NCP2-NCP1
 	  ;
@@ -759,7 +759,7 @@ incore(G) :- '$execute'(G).
 % standard meta-call, called if $execute could not do everything.
 %
 '$meta_call'(G, M) :-
-	yap_hacks:current_choice_point(CP),
+	'$current_choice_point'(CP),
 	'$call'(G, CP, G, M).
 
 
@@ -814,7 +814,7 @@ not(G) :-    \+ '$execute'(G).
 %
 '$meta_call'(G,_ISO,M) :-
 	'$iso_check_goal'(G,G),
-	yap_hacks:current_choice_point(CP),
+	'$current_choice_point'(CP),
 	'$call'(G, CP, G, M).
 
 '$meta_call'(G, CP, G0, M) :-
@@ -851,7 +851,7 @@ not(G) :-    \+ '$execute'(G).
 	).
 '$call'((X*->Y; Z),CP,G0,M) :- !,
 	(
-	 yap_hacks:current_choicepoint(DCP),
+	 '$current_choicepoint'(DCP),
 	 '$call'(X,CP,G0,M),
 	 yap_hacks:cut_at(DCP),
 	 '$call'(Y,CP,G0,M)
@@ -874,7 +874,7 @@ not(G) :-    \+ '$execute'(G).
 	).
 '$call'((X*->Y| Z),CP,G0,M) :- !,
 	(
-	 yap_hacks:current_choicepoint(DCP),
+	 '$current_choicepoint'(DCP),
 	 '$call'(X,CP,G0,M),
 	 yap_hacks:cut_at(DCP),
 	 '$call'(Y,CP,G0,M)
@@ -888,7 +888,7 @@ not(G) :-    \+ '$execute'(G).
 	    '$call'(B,CP,G0,M)
 	).
 '$call'(\+ X, _CP, _G0, M) :- !,
-	yap_hacks:current_choicepoint(CP),
+	'$current_choicepoint'(CP),
 	\+  '$call'(X,CP,G0,M).
 '$call'(not(X), _CP, _G0, M) :- !,
 	\+  '$call'(X,CP,G0,M).
@@ -1165,9 +1165,9 @@ expand_term(Term,Expanded) :-
 % where was the previous catch	
 catch(G, C, A) :-
 	'$catch'(C,A,_),
-	yap_hacks:current_choice_point(CP0),
+	'$$save_by'(CP0),
 	'$execute'(G),
-	yap_hacks:current_choice_point(CP1),
+	'$$save_by'(CP1),
 	(CP0 == CP1 -> !; true ).
 
 % makes sure we have an environment.
@@ -1182,9 +1182,9 @@ catch(G, C, A) :-
 '$system_catch'(G, M, C, A) :-
 	% check current trail
 	'$catch'(C,A,_),
-	yap_hacks:current_choice_point(CP0),
+	'$$save_by'(CP0),
 	'$execute_nonstop'(G, M),
-	yap_hacks:current_choice_point(CP1),
+	'$$save_by'(CP1),
 	(CP0 == CP1 -> !; true ).
 
 %
@@ -1264,13 +1264,24 @@ catch_ball(C, C).
 	).
 '$execute_outside_system_mode'(G, M, CP) :-
 	nb_getval('$trace', on), !,
-	'$do_spy'(G, M, CP, no).
-'$execute_outside_system_mode'(G, M, CP) :-
 	(
-	 yap_hacks:current_choice_point(CP1),
+	   '$$save_by'(CP1),
+	  '$do_spy'(G, M, CP, meta_creep),
+	   % we may exit system mode...
+	   '$$save_by'(CP2),
+	   (CP1 == CP2 -> ! ; ( true ; '$exit_system_mode', fail ) ),
+	   '$enter_system_mode'
+	;
+	   '$enter_system_mode',
+	   fail
+	).
+'$execute_outside_system_mode'(G, M, CP) :-
+	format('start~n', []),
+	(
+	 '$$save_by'(CP1),
 	 '$exit_system_mode',
 	 '$execute_nonstop'(G,M),
-	 yap_hacks:current_choice_point(CP2),
+	 '$$save_by'(CP2),
 	 (CP1 == CP2 -> ! ; ( true ; '$exit_system_mode', fail ) ),
 	 '$enter_system_mode'
 	;
diff --git a/pl/control.yap b/pl/control.yap
index de7665ba1..e3e678578 100644
--- a/pl/control.yap
+++ b/pl/control.yap
@@ -112,16 +112,16 @@ setup_call_catcher_cleanup(Setup, Goal, Catcher, Cleanup) :-
 	throw(Exception).
 
 '$safe_call_cleanup'(Goal, Cleanup, Catcher, Exception) :-
-	yap_hacks:current_choice_point(MyCP1),
+	'$current_choice_point'(MyCP1),
 	'$coroutining':freeze_goal(Catcher, '$clean_call'(Active, Cleanup)),
 	(
 	 yap_hacks:trail_suspension_marker(Catcher),
 	 yap_hacks:enable_interrupts,
-	 yap_hacks:current_choice_point(CP0),
+	 '$current_choice_point'(CP0),
 	 '$execute'(Goal),
 	 % ensure environment for delayed variables in Goal
 	 '$true',
-	 yap_hacks:current_choice_point(CPF),
+	 '$current_choice_point'(CPF),
 	 (
 	  CP0 =:= CPF
 	 ->
diff --git a/pl/debug.yap b/pl/debug.yap
index 3dfb6ebf4..f7b707631 100644
--- a/pl/debug.yap
+++ b/pl/debug.yap
@@ -287,10 +287,13 @@ debugging :-
 	'$execute_nonstop'(G,Mod).
 '$spy'([Mod|G]) :-
 	CP is '$last_choice_pt',	
+	'$enter_system_mode',
 	'$do_spy'(G, Mod, CP, spy).
 
 % last argument to do_spy says that we are at the end of a context. It
 % is required to know whether we are controlled by the debugger.
+%'$do_spy'(V, M, CP, Flag) :-
+%	writeln('$do_spy'(V, M, CP, Flag)), fail.
 '$do_spy'(V, M, CP, Flag) :-
 	var(V), !,
 	'$do_spy'(call(V), M, CP, Flag).
@@ -303,20 +306,20 @@ debugging :-
 '$do_spy'(M:G, _, CP, CalledFromDebugger) :- !,
 	'$do_spy'(G, M, CP, CalledFromDebugger).
 '$do_spy'((A,B), M, CP, CalledFromDebugger) :- !,
-	'$do_spy'(A, M, CP, yes),
+	'$do_spy'(A, M, CP, debugger),
 	'$do_spy'(B, M, CP, CalledFromDebugger).
 '$do_spy'((T->A;B), M, CP, CalledFromDebugger) :- !,
-	( '$do_spy'(T, M, CP, yes) -> '$do_spy'(A, M, CP, yes)
+	( '$do_spy'(T, M, CP, debugger) -> '$do_spy'(A, M, CP, CalledFromDebugger)
 	;
 	  '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
 '$do_spy'((T->A|B), M, CP, CalledFromDebugger) :- !,
-	( '$do_spy'(T, M, CP, debugger) -> 	'$do_spy'(A, M, CP, yes)
+	( '$do_spy'(T, M, CP, debugger) -> 	'$do_spy'(A, M, CP, CalledFromDebugger)
 	;
 	  '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
-'$do_spy'((T->A), M, CP, _) :- !,
-	( '$do_spy'(T, M, CP, yes) -> '$do_spy'(A, M, CP, yes) ).
+'$do_spy'((T->A), M, CP, CalledFromDebugger) :- !,
+	( '$do_spy'(T, M, CP, debugger) -> '$do_spy'(A, M, CP,  CalledFromDebugger) ).
 '$do_spy'((A;B), M, CP, CalledFromDebugger) :- !,
 	(
 	  '$do_spy'(A, M, CP, CalledFromDebugger)
@@ -344,7 +347,7 @@ debugging :-
 % we are skipping, so we can just call the goal,
 % while leaving the minimal structure in place.
 '$loop_spy'(GoalNumber, G, Module, CalledFromDebugger) :-
-	yap_hacks:current_choice_point(CP),
+	'$current_choice_point'(CP),
 	'$system_catch'('$loop_spy2'(GoalNumber, G, Module, CalledFromDebugger, CP),
 		    Module, error(Event,Context),
 		    '$loop_spy_event'(error(Event,Context), GoalNumber, G, Module, CalledFromDebugger)).
@@ -404,6 +407,8 @@ debugging :-
 	    /* call port */
 	    '$enter_goal'(GoalNumber, G, Module),
 	    '$spycall'(G, Module, CalledFromDebugger, Retry),
+	    % make sure we are in system mode when running the debugger.
+	    '$enter_system_mode',
 	    (
 	      '$debugger_deterministic_goal'(G) ->
 	      Det=true
@@ -428,6 +433,8 @@ debugging :-
 	      ),
 	      '$continue_debugging'(exit, CalledFromDebugger)	   
 	     ;
+	       % make sure we are in system mode when running the debugger.
+	       '$enter_system_mode',
 		/* backtracking from exit				*/
 	        /* we get here when we want to redo a goal		*/
 		/* redo port */
@@ -443,6 +450,7 @@ debugging :-
 	     fail			/* to backtrack to spycalls	*/
 	     )
 	  ;
+	    '$enter_system_mode',
 	    '$show_trace'(fail,G,Module,GoalNumber,_), /* inform at fail port		*/
 	    '$continue_debugging'(fail, CalledFromDebugger),
 	    /* fail port */
@@ -510,7 +518,7 @@ debugging :-
 	CP is '$last_choice_pt',
 	'$clause'(G, M, Cl, _),
 	% I may backtrack to here from far away
-	( '$do_spy'(Cl, M, CP, CalledFromDebugger) ; InRedo = true ).
+	( '$do_spy'(Cl, M, CP, debugger) ; InRedo = true ).
 '$spycall'(G, M, CalledFromDebugger, InRedo) :-
 	'$undefined'(G, M), !,
 	'$find_goal_definition'(M, G, NM, Goal),
@@ -528,11 +536,11 @@ debugging :-
 
 '$meta_creep'(G,M) :-
 	(
-	 yap_hacks:current_choice_point(CP1),
+	 '$$save_by'(CP1),
 	 '$exit_system_mode',
 	 '$meta_creep',
 	 '$execute_nonstop'(G,M),
-	 yap_hacks:current_choice_point(CP2),
+	 '$$save_by'(CP2),
 	 (CP1 == CP2 -> ! ; ( true ; '$exit_system_mode', '$meta_creep', fail ) ),
 	 '$enter_system_mode'
 	;
@@ -544,6 +552,8 @@ debugging :-
 	'$flags'(G,M,F,F),
 	F /\ 0x00000040 =\= 0.
 
+%'$trace'(P,G,Module,L,Deterministic) :-
+%	'$nb_getval'('$system_mode',On,fail), writeln(On), fail.
 '$trace'(P,G,Module,L,Deterministic) :-
 	% at this point we are done with leap or skip
 	nb_setval('$debug_run',off),
@@ -730,24 +740,34 @@ debugging :-
 
 % first argument is exit, zip or fail
 % second is creep, meta_creep, spy, or debugger
-'$continue_debugging'(exit, debugger) :- !.
-'$continue_debugging'(zip, debugger) :- !.
-'$continue_debugging'(fail, debugger) :- !.
+%'$continue_debugging'(Exit, Debugger) :-
+%	writeln('$continue_debugging'(Exit, Debugger)), fail.
+% that's what follows
+'$continue_debugging'(_, debugger) :- !.
 % do not need to debug!
+% go back to original sequence.
+'$continue_debugging'(zip, _) :- !, '$exit_system_mode'.
+'$continue_debugging'(fail, _) :- !.
 '$continue_debugging'(exit, meta_creep) :- !,
+	 '$exit_system_mode',
 	'$meta_creep'.
-'$continue_debugging'(_, no) :-
+'$continue_debugging'(_, creep) :- !,
+	 '$exit_system_mode',
 	'$creep'.
+'$continue_debugging'(_, spy) :- !,
+	 '$exit_system_mode',
+	'$creep'.
+'$continue_debugging'(_, _) :- '$exit_system_mode'.
 
 % if we are in the interpreter, don't need to care about forcing a trace, do we?
-'$continue_debugging_goal'(_, yes,G) :- !,
+'$continue_debugging_goal'(yes,G) :- !,
 	'$execute_dgoal'(G).
 % do not need to debug!
-'$continue_debugging_goal'(_, _,G) :-
+'$continue_debugging_goal'(_,G) :-
 	'nb_getval'('$debug_run',Zip),
         (Zip == nodebug ;  number(Zip) ; Zip == spy ), !,
 	'$execute_dgoal'(G).
-'$continue_debugging_goal'(_, _,G) :-
+'$continue_debugging_goal'(_,G) :-
 	'$execute_creep_dgoal'(G).
 	
 '$execute_dgoal'('$execute_nonstop'(G,M)) :-
diff --git a/pl/hacks.yap b/pl/hacks.yap
index 4ae8aef43..015d28379 100644
--- a/pl/hacks.yap
+++ b/pl/hacks.yap
@@ -47,7 +47,7 @@ code_location(Info,Where,Location) :-
 	integer(Where) , !,
 	'$pred_for_code'(Where,Name,Arity,Mod,Clause),
 	construct_code(Clause,Name,Arity,Mod,Info,Location).
-code_location(Info,_,Info).
+code_location(Ixnfo,_,Info).
 
 construct_code(-1,Name,Arity,Mod,Where,Location) :- !,
 	number_codes(Arity,ArityCode),
diff --git a/pl/signals.yap b/pl/signals.yap
index ae553a988..bd629c42c 100644
--- a/pl/signals.yap
+++ b/pl/signals.yap
@@ -88,6 +88,9 @@
 	'$current_module'(M0),
 	'$execute0'((Goal,M:G),M0).
 
+% we may be creeping outside and coming back to system mode.
+'$start_creep'([_|'$enter_system_mode'], _) :- !,
+	'$enter_system_mode'.
 '$start_creep'([Mod|G], _) :-
 	'$in_system_mode', !,
 	'$execute0'(G, Mod).