fix segv in regcomp.c:S_join_exact()

[ cherry-picked from bb789b09de07edfb74477eb1603949c96d60927d
to stop clang's address-sanitizer from complaining. See [perl #115994] ]

This function joins multiple EXACT* nodes into a single node.
At the end, under DEBUGGING, it marks the optimised-out nodes as being
type OPTIMIZED. However, some of the 'nodes' aren't actually nodes;
they're random bits of string at the tail of those nodes. So you
can't peek that the 'node's OP field to decide what type it was.

Instead, just unconditionally overwrite all the slots with fake
OPTIMIZED nodes.

1 files changed, 5 insertions, 5 deletions

diff --git a/regcomp.c b/regcomp.c
index b186c8d962..b30e3bc739 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -2647,13 +2647,13 @@ S_join_exact(pTHX_ RExC_state_t *pRExC_state, regnode *scan, I32 *min, U32 flags
     }
     
 #ifdef DEBUGGING
-    /* Allow dumping */
+    /* Allow dumping but overwriting the collection of skipped
+     * ops and/or strings with fake optimized ops */
     n = scan + NODE_SZ_STR(scan);
     while (n <= stop) {
-        if (PL_regkind[OP(n)] != NOTHING || OP(n) == NOTHING) {
-            OP(n) = OPTIMIZED;
-            NEXT_OFF(n) = 0;
-        }
+	OP(n) = OPTIMIZED;
+	FLAGS(n) = 0;
+	NEXT_OFF(n) = 0;
         n++;
     }
 #endif