diff --git a/C/args.c b/C/args.c
index 2b9ab8e09..140acfc41 100644
--- a/C/args.c
+++ b/C/args.c
@@ -38,6 +38,7 @@ int Yap_ArgKey(Atom key, const param_t *def, int n) {
   return -1;
 }
 
+#define YAP_XARGINFO(Error, Message)
 #define failed(e, t, a) failed__(e, t, a PASS_REGS)
 
 static xarg *failed__(yap_error_number e, Term t, xarg *a USES_REGS) {
diff --git a/C/c_interface.c b/C/c_interface.c
index 909ab6ea0..4a845d653 100755
--- a/C/c_interface.c
+++ b/C/c_interface.c
@@ -1721,6 +1721,7 @@ X_API bool YAP_EnterGoal(YAP_PredEntryPtr ape, CELL *ptr, YAP_dogoalinfo *dgi) {
   CACHE_REGS
   PredEntry *pe = ape;
   bool out;
+   fprintf(stderr,"EnterGoal: H=%d ENV=%p B=%d TR=%d P=%p CP=%p Slots=%d\n",HR-H0,LCL0-ENV,LCL0-(CELL*)B,(CELL*)TR-LCL0, P, CP, LOCAL_CurSlot);
 
   BACKUP_MACHINE_REGS();
   LOCAL_ActiveError->errorNo = YAP_NO_ERROR;
@@ -1741,7 +1742,7 @@ X_API bool YAP_EnterGoal(YAP_PredEntryPtr ape, CELL *ptr, YAP_dogoalinfo *dgi) {
   //fprintf(stderr,"PrepGoal: H=%d ENV=%p B=%d TR=%d P=%p CP=%p Slots=%d\n",
 	//  HR-H0,LCL0-ENV,LCL0-(CELL*)B,(CELL*)TR-LCL0, P, CP, LOCAL_CurSlot);
   out = Yap_exec_absmi(true, false);
-   fprintf(stderr,"LeaveGoal success=%d: H=%d ENV=%p B=%d TR=%d P=%p CP=%p Slots=%d\n", out,HR-H0,LCL0-ENV,LCL0-(CELL*)B,(CELL*)TR-LCL0, P, CP, LOCAL_CurSlot);
+   fprintf(stderr,"EnterGoal success=%d: H=%d ENV=%p B=%d TR=%d P=%p CP=%p Slots=%d\n", out,HR-H0,LCL0-ENV,LCL0-(CELL*)B,(CELL*)TR-LCL0, P, CP, LOCAL_CurSlot);
   if (out) {
     dgi->EndSlot = LOCAL_CurSlot;
     Yap_StartSlots();
@@ -1767,7 +1768,7 @@ X_API bool YAP_RetryGoal(YAP_dogoalinfo *dgi) {
     return false;
   }
   if (B < myB) {
-    // get rid of garbage choice-points 
+    // get rid of garbage choice-points
     B = myB;
   }
   //fprintf(stderr,"RetryGoal: H=%d ENV=%p B=%d TR=%d P=%p CP=%p Slots=%d\n",
@@ -1791,43 +1792,48 @@ X_API bool YAP_RetryGoal(YAP_dogoalinfo *dgi) {
 X_API bool YAP_LeaveGoal(bool successful, YAP_dogoalinfo *dgi) {
   CACHE_REGS
   choiceptr myB;
+  bool backtrack = false;
 
-   fprintf(stderr,"LeaveGoal success=%d: H=%d ENV=%p B=%d TR=%d P=%p CP=%p Slots=%d\n",
-	    successful,HR-H0,LCL0-ENV,LCL0-(CELL*)B,(CELL*)TR-LCL0, P, CP, LOCAL_CurSlot);
+   fprintf(stderr,"LeaveGoal success=%d: H=%d ENV=%p B=%ld myB=%ld TR=%d P=%p CP=%p Slots=%d\n",
+	   successful,HR-H0,LCL0-ENV,LCL0-(CELL*)B,dgi->b0,(CELL*)TR-LCL0, P, CP, LOCAL_CurSlot);
   BACKUP_MACHINE_REGS();
-  myB = (choiceptr)(LCL0 - dgi->b0);
-  if (B < myB) {
+  myB = (choiceptr)(LCL0 - dgi->b);
+  if (B > myB) {
     /* someone cut us */
     return false;
   }
   /* prune away choicepoints */
-  while (B != myB) {
+  while (B && B->cp_b && B < myB && B->cp_b < myB) {
 #ifdef YAPOR
-    CUT_prune_to(myB);
+    CUT_prune_to(B);
 #endif
-    B = myB;
+    if (successful) {
+    B = B->cp_b;
+    trim_trail();
+    } else {
+    P = TRUSTFAILCODE;
+    Yap_exec_absmi(true, YAP_EXEC_ABSMI);
+    }
   }
   /* if backtracking asked for, recover space and bindings */
-  if (!successful) {
-    P = FAILCODE;
-    Yap_exec_absmi(true, YAP_EXEC_ABSMI);
+#if 0
+  if (0 && !successful) {
     /* recover stack space */
     HR = B->cp_h;
     TR = B->cp_tr;
 #ifdef DEPTH_LIMIT
     DEPTH = B->cp_depth;
 #endif /* DEPTH_LIMIT */
-    
+
     YENV = ENV = B->cp_env;
   } else {
     Yap_TrimTrail();
   }
+  #endif
 /* recover local stack */
 #ifdef DEPTH_LIMIT
   DEPTH = ENV[E_DEPTH];
 #endif
-  /* make sure we prune C-choicepoints */
-  ENV = (CELL *)(ENV[E_E]);
   /* ASP should be set to the top of the local stack when we
      did the call */
   ASP = B->cp_env;
@@ -1835,7 +1841,9 @@ X_API bool YAP_LeaveGoal(bool successful, YAP_dogoalinfo *dgi) {
   YENV = ENV = (CELL *)((B->cp_env)[E_E]);
   B = B->cp_b;
   // SET_BB(B);
-  HB = PROTECT_FROZEN_H(B);
+  if (B) {
+    HB = PROTECT_FROZEN_H(B);
+  }
   CP = dgi->cp;
   P = dgi->p;
   LOCAL_CurSlot = dgi->CurSlot;
@@ -2279,7 +2287,7 @@ X_API bool YAP_CompileClause(Term t) {
   Term mod = CurrentModule;
   Term tn = TermNil;
   bool ok = true;
-  
+
   BACKUP_MACHINE_REGS();
 
   /* allow expansion during stack initialization */
@@ -2307,7 +2315,7 @@ X_API bool YAP_CompileClause(Term t) {
   }
   RECOVER_MACHINE_REGS();
   if (!ok) {
-      return NULL;        
+      return NULL;
   }
   return ok;
 }
diff --git a/C/stack.c b/C/stack.c
index bd94e882a..dca9a36db 100644
--- a/C/stack.c
+++ b/C/stack.c
@@ -115,7 +115,7 @@ static PredEntry *PredForChoicePt(yamop *p_code, op_numbers *opn) {
       *opn = opnum;
     switch (opnum) {
     case _Nstop:
-      return NULL;
+      return PredFail;
     case _jump:
       p_code = p_code->y_u.l.l;
       break;
@@ -284,8 +284,9 @@ bool Yap_search_for_static_predicate_in_use(PredEntry *p,
     }
     /* now mark the choicepoint */
 
-    if (b_ptr)
+    if (b_ptr) {
       pe = PredForChoicePt(b_ptr->cp_ap, NULL);
+    }
     else
       return false;
     if (pe == p) {
diff --git a/CXX/yapi.cpp b/CXX/yapi.cpp
index f2ef45a51..b63a75cee 100644
--- a/CXX/yapi.cpp
+++ b/CXX/yapi.cpp
@@ -559,7 +559,7 @@ bool YAPEngine::mgoal(Term t, Term tmod, bool release) {
       return result;
   } catch (...) {
       YAPCatchError();
-      
+
       return false;
     }
 }
@@ -736,10 +736,11 @@ bool YAPQuery::next() {
   }
   q_state = 1;
   __android_log_print(ANDROID_LOG_INFO, "YAPDroid", "out  %d", result);
-
+if (!result) {
     YAP_LeaveGoal(result, &q_h);
     Yap_CloseHandles(q_handles);
     q_open = false;
+  }
     YAPCatchError();
   RECOVER_MACHINE_REGS();
   LOCAL_RestartEnv = oldp;
@@ -1047,7 +1048,7 @@ std::stringstream s;
 void YAPEngine::reSet() {
   /* ignore flags  for now */
   BACKUP_MACHINE_REGS();
-  
+
   choiceptr b = (choiceptr)(LCL0-q.b);
   if (b > B) B = b;
   P = FAILCODE;
diff --git a/packages/python/swig/prolog/yapi.yap b/packages/python/swig/prolog/yapi.yap
index c3b47b9ef..cd71eb323 100644
--- a/packages/python/swig/prolog/yapi.yap
+++ b/packages/python/swig/prolog/yapi.yap
@@ -82,7 +82,9 @@ python_query( Caller, String ) :-
 in_dict(Dict, var([V0,V|Vs])) :- !,
 	Dict[V] := V0,
 	in_dict( Dict, var([V0|Vs])).
+in_dict(Dict, var([],_G)) :- !.
 in_dict(Dict, nonvar([V0|Vs],G)) :- !,
 	Dict[V0] := G,
 	in_dict( Dict, var([V0|Vs])).
+in_dict(Dict, nonvar([],_G)) :- !.
 in_dict(_, _).
diff --git a/packages/python/swig/yap4py/yapi.py b/packages/python/swig/yap4py/yapi.py
index fa49a9980..056d8691d 100644
--- a/packages/python/swig/yap4py/yapi.py
+++ b/packages/python/swig/yap4py/yapi.py
@@ -56,7 +56,8 @@ class Predicate( YAPPredicate ):
 class Query:
     """Goal is a predicate instantiated under a specific environment """
     def __init__(self, engine, g):
-        engine.reSet();
+        engine.reSet()
+        self.engine = engine
         self.q = engine.query(g)
         if self.q:
             self.port = "call"
@@ -71,8 +72,8 @@ class Query:
         if not self.q:
             raise StopIteration()
         if self.q.next():
-            rc = self.answer
-            if self.port == "exit":
+            rc = self.q.answer
+            if self.q.port == "exit":
                 return rc
         else:
             if self:
@@ -80,7 +81,6 @@ class Query:
             raise StopIteration()
 
     def close( self ):
-        engine.reSet()
         if self.q:
             self.q.close()
             self.q = None
@@ -138,7 +138,7 @@ class YAPShell:
         #        # vs is the list of variables
         # you can print it out, the left-side is the variable name,
         # the right side wraps a handle to a variable
-        #import pdb; pdb.set_trace()
+        import pdb; pdb.set_trace()
         #     #pdb.set_trace()
         # atom match either symbols, or if no symbol exists, sttrings, In this case
         # variable names should match strings
@@ -148,7 +148,7 @@ class YAPShell:
         #        return
         try:
             engine = self.engine
-            bindings    = []
+            bindings   = []
             loop = False
             if g:
                 g.release()
@@ -158,7 +158,7 @@ class YAPShell:
                 bindings += [bind]
                 if loop:
                     continue
-                if not self.q.port == "exit":
+                if self.q.port == "exit":
                     break
                 s = input("more(;),  all(*), no(\\n), python(#) ?").lstrip()
                 if s.startswith(';') or s.startswith('y'):
@@ -174,7 +174,7 @@ class YAPShell:
                 else:
                     break
             if self.q:
-                self.os = query
+                self.q.close()
             if bindings:
                 return True,bindings
             print("No (more) answers")
@@ -182,6 +182,7 @@ class YAPShell:
         except Exception as e:
             if not self.q:
                 return False, None
+            self.q.close()
             print("Exception")
             return False, None
 
diff --git a/pl/attributes.yap b/pl/attributes.yap
index 2bf9a611d..1b53282b4 100644
--- a/pl/attributes.yap
+++ b/pl/attributes.yap
@@ -26,7 +26,7 @@
 */
 
 :- module( attributes, [delayed_goals/4,
-all_attvars/1,	
+all_attvars/1,
         bind_attvar/1,
         del_all_atts/1,
         del_all_module_atts/2,
@@ -36,7 +36,7 @@ all_attvars/1,
         put_att_term/2,
         put_module_atts/2,
         unbind_attvar/1,
-        woken_att_do/4] .
+        woken_att_do/4]) .
 
 :- use_system_module( '$_boot', ['$undefp'/1]).
 
diff --git a/pl/ypp.yap b/pl/ypp.yap
index bbb648b3f..489a080e6 100644
--- a/pl/ypp.yap
+++ b/pl/ypp.yap
@@ -2,17 +2,17 @@
  * @file   ypp.yap
  * @author Nuno Fonseca (nunofonseca@acm.org), Tiago Soares
  * @date  2005-05-14
- * 
+ *
  * @brief  Yap PreProcessing
- * 
- * 
+ *
+ *
 */
 %====================================================================================
 %
 % YPP: Yap PreProcessing
 %
 % Author: Nuno Fonseca (nunofonseca@acm.org)
-% Date: 
+% Date:
 % $Id: ypp.yap,v 1.4 2006-03-07 17:30:47 tiagosoares Exp $
 %
 %====================================================================================
@@ -33,14 +33,16 @@
 
 /**
  * @defgroup ypp Yap PreProcessing
+ * @{
  * @ingroup library
  *
- * This program_continuation can be used as a preprocessor in the
+ * This program can be used as a preprocessor in the
  * style of the `C` language. Currently, it must be used through
  * ypp_consult and or ypp_reconsult.
  *
- * Notice that ypp uses `#` commands.
- * 
+ * Notice that ypp uses `#` commands and it is different from the Prolog if/1
+ * directive.
+ *
  */
 
 %====================================================================================
@@ -140,3 +142,5 @@ ypp_file(File,PPFile):-
 :-set_state(on),
 	ypp_extcmd('cpp -P -E -w -o ').
 %	ypp_extcmd('gpp -o').
+
+%% @}