(PUSH_FAILURE_POINT, POP_FAILURE_POINT): Don't push or pop

register values if POSIX backtracking is turned off.
(NUM_FAILURE_ITEMS): Value is 0 if no POSIX backtracking.

src/regex.c

@@ -1153,6 +1153,7 @@ typedef struct
     /* Push the info, starting with the registers.  */			\
     DEBUG_PRINT1 ("\n");						\
 									\
+    if (!RE_NO_POSIX_BACKTRACKING & bufp->syntax)			\
       for (this_reg = lowest_active_reg; this_reg <= highest_active_reg; \
 	   this_reg++)							\
 	{								\
@@ -1213,7 +1214,9 @@ typedef struct
 
 /* We actually push this many items.  */
 #define NUM_FAILURE_ITEMS				\
-  ((highest_active_reg - lowest_active_reg + 1) * NUM_REG_ITEMS 	\
+  (((RE_NO_POSIX_BACKTRACKING & bufp->syntax		\
+     ? 0 : highest_active_reg - lowest_active_reg + 1)	\
+    * NUM_REG_ITEMS)					\
    + NUM_NONREG_ITEMS)
 
 /* How many items can still be added to the stack without overflowing it.  */
@@ -1272,6 +1275,7 @@ typedef struct
   low_reg = (unsigned) POP_FAILURE_INT ();				\
   DEBUG_PRINT2 ("  Popping  low active reg: %d\n", low_reg);		\
 									\
+  if (!RE_NO_POSIX_BACKTRACKING & bufp->syntax)				\
     for (this_reg = high_reg; this_reg >= low_reg; this_reg--)		\
       {									\
 	DEBUG_PRINT2 ("    Popping reg: %d\n", this_reg);		\