export current predicate for SWI built-ins.

packages/PLStream/pl-error.c

@@ -379,6 +379,10 @@ X_API int PL_error(const char *pred, int arity, const char *msg, int id, ...)
     goto err_instantiation;
   }
   va_end(args);
+  if (!pred) {
+    pred = Yap_GetCurrentPredName();
+    arity = Yap_GetCurrentPredArity();
+  }
   if ( pred )
     { PL_unify_term(predterm,
 		    PL_FUNCTOR, FUNCTOR_divide2,

packages/PLStream/pl-yap.h

@@ -29,6 +29,10 @@ typedef YAP_Term	       *Word;		/* Anonymous 4 byte object */
 typedef YAP_Atom		Atom;
 typedef YAP_Term		(*Func)();	/* foreign functions */
 
+const char *Yap_GetCurrentPredName(void);
+YAP_Int     Yap_GetCurrentPredArity(void);
+
+
 extern atom_t codeToAtom(int chrcode);
 
 #define valTermRef(t)    ((Word)YAP_AddressFromSlot(t))