From f592693c9b50765a4db421d53b6e2e04c45a2ee6 Mon Sep 17 00:00:00 2001
From: jzmaddock <john@johnmaddock.co.uk>
Date: Sat, 7 Oct 2017 17:23:59 +0100
Subject: [PATCH] Regex: Fix potential negation of INT_MIN, see
 https://oss-fuzz.com/v2/testcase-detail/6646578892767232?noredirect=1.

---
 include/boost/regex/v4/perl_matcher_common.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/boost/regex/v4/perl_matcher_common.hpp b/include/boost/regex/v4/perl_matcher_common.hpp
index f08e9d43..a0973da9 100644
--- a/include/boost/regex/v4/perl_matcher_common.hpp
+++ b/include/boost/regex/v4/perl_matcher_common.hpp
@@ -777,7 +777,7 @@ inline bool perl_matcher<BidiIterator, Allocator, traits>::match_assert_backref(
    {
       // Have we recursed into subexpression "index"?
       // If index == 0 then check for any recursion at all, otherwise for recursion to -index-1.
-      int idx = -index-1;
+      int idx = -(index+1);
       if(idx >= 10000)
       {
          named_subexpressions::range_type r = re.get_data().equal_range(idx);