From 660d2b53b1206e868d5470eee80b5e62d7e30da7 Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Tue, 6 Sep 2022 23:55:09 +0430
Subject: [PATCH] LibRegex: Account for eof after \<x> when 'x' leads to legacy
 behaviour

---
 Tests/LibRegex/Regex.cpp                    | 1 +
 Userland/Libraries/LibRegex/RegexParser.cpp | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/Tests/LibRegex/Regex.cpp b/Tests/LibRegex/Regex.cpp
index 2b4da92c983..abcfa935134 100644
--- a/Tests/LibRegex/Regex.cpp
+++ b/Tests/LibRegex/Regex.cpp
@@ -603,6 +603,7 @@ TEST_CASE(ECMA262_parse)
         { "(?<𝓑𝓻𝓸𝔀𝓷>a)"sv },
         { "((?=lg)?[vl]k\\-?\\d{3}) bui| 3\\.[-\\w; ]{10}lg?-([06cv9]{3,4})"sv, regex::Error::NoError, ECMAScriptFlags::BrowserExtended }, // #12373, quantifiable assertions.
         { parse_test_case_long_disjunction_chain.view() },                                                                                 // A whole lot of disjunctions, should not overflow the stack.
+        { "(\"|')(?:(?!\\2)[^\\\\\\r\\n]|\\\\.)*\\2"sv, regex::Error::NoError, ECMAScriptFlags::BrowserExtended },                         // LegacyOctalEscapeSequence should not consume too many chars (and should not crash)
     };
 
     for (auto& test : tests) {
diff --git a/Userland/Libraries/LibRegex/RegexParser.cpp b/Userland/Libraries/LibRegex/RegexParser.cpp
index 557632c6507..b37a85651ee 100644
--- a/Userland/Libraries/LibRegex/RegexParser.cpp
+++ b/Userland/Libraries/LibRegex/RegexParser.cpp
@@ -1582,7 +1582,7 @@ bool ECMA262Parser::parse_atom_escape(ByteCode& stack, size_t& match_length_mini
         }
 
         // If not, put the characters back.
-        back(escape_str.length());
+        back(escape_str.length() + (done() ? 0 : 1));
     }
 
     Vector<CompareTypeAndValuePair> escape_compares;