#define MgTAINTEDDIR_on(mg) (mg->mg_flags |= MGf_TAINTEDDIR)
#define MgTAINTEDDIR_off(mg) (mg->mg_flags &= ~MGf_TAINTEDDIR)
-#define MgPV(mg) ((mg)->mg_len == HEf_SVKEY) ? \
- SvPV((SV*)((mg)->mg_ptr),na) : \
- (mg)->mg_ptr
+#define MgPV(mg,lp) (((lp = (mg)->mg_len) == HEf_SVKEY) ? \
+ SvPV((SV*)((mg)->mg_ptr),lp) : \
+ (mg)->mg_ptr)