joni-nullcheck.diff

diff -r 524852d0cc0d src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/regexp/joni/StackMachine.java
--- a/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/regexp/joni/StackMachine.java	Mon Mar 16 18:13:38 2015 +0100
+++ b/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/regexp/joni/StackMachine.java	Wed Mar 18 22:40:47 2015 +0100
@@ -405,6 +405,7 @@
                     int endp;
                     isNull = 1;
                     while (k < stk) {
+                        e = stack[k++];
                         if (e.type == MEM_START) {
                             if (e.getMemEnd() == INVALID_INDEX) {
                                 isNull = 0;
@@ -415,15 +416,12 @@
                             } else {
                                 endp = e.getMemEnd();
                             }
-                            if (stack[e.getMemStart()].getMemPStr() != endp) {
-                                isNull = 0;
+                            if (e.getMemPStr() != endp || endp != s) {
+                                isNull = 0; /* not empty or position did change */
                                 break;
-                            } else if (endp != s) {
-                                isNull = -1; /* empty, but position changed */
                             }
+                            isNull = -1;
                         }
-                        k++;
-                        e = stack[k]; // !!
                     }
                     break;
                 }