fix EX: it cannot be a term and it should be a placeholder for BallTerm,

so the twp can never be alive at the same time.

C/absmi.c

@@ -7542,13 +7542,16 @@ Yap_absmi(int inp)
 	save_machine_regs();
 
 	SREG = (CELL *) YAP_Execute(p, p->cs.f_code);
-	EX = 0L;
       }
       Yap_CloseSlots();
-
-      restore_machine_regs();
       setregs();
       Yap_PrologMode = UserMode;
+      restore_machine_regs();
+      if (EX) {
+	struct DB_TERM *exp = EX;
+	EX = NULL;
+	Yap_JumpToEnv(Yap_PopTermFromDB(exp));
+      }
       if (!SREG) {
 	FAIL();
       }

C/c_interface.c

@@ -2040,7 +2040,24 @@ YAP_GoalHasException(Term *t)
   int out = FALSE;
   BACKUP_MACHINE_REGS();
   if (EX) {
-    *t = EX;
+    do {
+      *t = Yap_FetchTermFromDB(EX);
+      if (Yap_Error_TYPE == OUT_OF_ATTVARS_ERROR) {
+	Yap_Error_TYPE = YAP_NO_ERROR;
+	if (!Yap_growglobal(NULL)) {
+	  Yap_Error(OUT_OF_ATTVARS_ERROR, TermNil, Yap_ErrorMessage);
+	  RECOVER_MACHINE_REGS();
+	  return FALSE;
+	}
+      } else {
+	Yap_Error_TYPE = YAP_NO_ERROR;
+	if (!Yap_growstack(EX->NOfCells*CellSize)) {
+	  Yap_Error(OUT_OF_STACK_ERROR, TermNil, Yap_ErrorMessage);
+	  RECOVER_MACHINE_REGS();
+	  return FALSE;
+	}
+      }
+    } while (*t == (CELL)0);
     out = TRUE;
   }
   RECOVER_MACHINE_REGS();
@@ -2051,7 +2068,11 @@ X_API void
 YAP_ClearExceptions(void)
 {
   Yap_ResetExceptionTerm();
-  EX = 0L;
+  if (EX) {
+    BallTerm = EX;
+  }
+  EX = NULL;
+  Yap_ResetExceptionTerm();    
   UncaughtThrow = FALSE;
 }
 

C/exec.c

@@ -1007,7 +1007,7 @@ init_stack(int arity, CELL *pt, int top, choiceptr saved_b)
   /* create an initial pseudo environment so that when garbage
      collection is going up in the environment chain it doesn't get
      confused */
-  EX = 0L;
+  EX = NULL;
   //  sl = Yap_InitSlot(t);
   YENV = ASP;
   YENV[E_CP] = (CELL)P;
@@ -1502,7 +1502,8 @@ JumpToEnv(Term t) {
 	  B = handler;
 	else 
 	  previous->cp_b = handler;
-	EX = t;
+	EX = BallTerm;
+	BallTerm = NULL;
 	P = (yamop *)FAILCODE;
 	HB = B->cp_h;
 	return TRUE;
@@ -1622,7 +1623,7 @@ Yap_InitYaamRegs(void)
   LOCK(SignalLock);
   CreepFlag = CalculateStackGap();
   UNLOCK(SignalLock);
-  EX = 0L;
+  EX = NULL;
   init_stack(0, NULL, TRUE, NULL);
   /* the first real choice-point will also have AP=FAIL */ 
   CurSlot = 0;
@@ -1725,7 +1726,7 @@ static Int
 p_reset_exception(void)
 {
   Term t;
-  EX = 0L;
+  EX = NULL;
   t = GetException();
   if (!t) 
     return FALSE;

H/Regs.h

@@ -110,7 +110,7 @@ typedef struct
     CELL  *AuxSp_;		/* 9 Auxiliary stack pointer                  */
     ADDR   AuxTop_;		/* 10 Auxiliary stack top                     */
 /* visualc*/
-    CELL   EX_;	    	        /* 18                                         */
+    struct DB_TERM   * EX_;     /* 18                                         */
     Term  CurrentModule_;
 #if defined(SBA) || defined(TABLING)
     CELL *H_FZ_;

library/yap2swi/yap2swi.c

@@ -2444,7 +2444,7 @@ PL_exception(qid_t q)
 X_API void
 PL_clear_exception(void)
 {
-  EX = 0L;
+  EX = NULL;
 }
 
 X_API int