From 695fc3c5465ef1ea166eeba35dfdd883133efbd3 Mon Sep 17 00:00:00 2001
From: MarkLee131 <kaixuan.li@ntu.edu.sg>
Date: Mon, 30 Mar 2026 22:26:44 +0800
Subject: [PATCH] re2: fix mark deduplication flag in Workq::mark()

Workq::mark() sets last_was_mark_ to false after inserting a mark.
It should set it to true so that a subsequent call to mark() without
an intervening insert() is correctly deduplicated.

This is a correctness bug that affects longest-match mode. Duplicate
marks can cause incorrect match priority ordering.
---
 re2/dfa.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/re2/dfa.cc b/re2/dfa.cc
index d587a552..525bd407 100644
--- a/re2/dfa.cc
+++ b/re2/dfa.cc
@@ -388,7 +388,7 @@ class DFA::Workq : public SparseSet {
   void mark() {
     if (last_was_mark_)
       return;
-    last_was_mark_ = false;
+    last_was_mark_ = true;
     SparseSet::insert_new(nextmark_++);
   }