From ee1d9217aa8dd25442ea4593836c998dfd7f49fb Mon Sep 17 00:00:00 2001
From: AnotherTest <ali.mpfard@gmail.com>
Date: Mon, 28 Dec 2020 09:07:17 +0330
Subject: [PATCH] LibRegex: Fail early if eof seen after '(?'

Fixes #4583.
---
 Libraries/LibRegex/RegexParser.cpp | 5 +++++
 Libraries/LibRegex/Tests/Regex.cpp | 1 +
 2 files changed, 6 insertions(+)

diff --git a/Libraries/LibRegex/RegexParser.cpp b/Libraries/LibRegex/RegexParser.cpp
index 6015212123d..2afbad64c7f 100644
--- a/Libraries/LibRegex/RegexParser.cpp
+++ b/Libraries/LibRegex/RegexParser.cpp
@@ -741,6 +741,11 @@ bool ECMA262Parser::parse_assertion(ByteCode& stack, [[maybe_unused]] size_t& ma
         if (!try_skip("(?"))
             return false;
 
+        if (done()) {
+            set_error(Error::InvalidCaptureGroup);
+            return false;
+        }
+
         ByteCode assertion_stack;
         size_t length_dummy = 0;
 
diff --git a/Libraries/LibRegex/Tests/Regex.cpp b/Libraries/LibRegex/Tests/Regex.cpp
index e4fb05c3c4e..0bb2e8d2ef7 100644
--- a/Libraries/LibRegex/Tests/Regex.cpp
+++ b/Libraries/LibRegex/Tests/Regex.cpp
@@ -500,6 +500,7 @@ TEST_CASE(ECMA262_parse)
         { "(?", regex::Error::InvalidCaptureGroup },
         { "\\u1234", regex::Error::NoError, regex::ECMAScriptFlags::Unicode },
         { "[\\u1234]", regex::Error::NoError, regex::ECMAScriptFlags::Unicode },
+        { ",(?", regex::Error::InvalidCaptureGroup }, // #4583
     };
 
     for (auto& test : tests) {