From 97f7132b822d0b36cbd47690fa4558480d4a7755 Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Sat, 10 Jul 2021 13:19:47 +0430
Subject: [PATCH] expr: Use Basic Posix regular expressions

Dr.POSIX requires expr to use BREs, so let's use BREs.
Fixes #8506.
---
 Userland/Utilities/expr.cpp | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/Userland/Utilities/expr.cpp b/Userland/Utilities/expr.cpp
index d8371d5318..253adce1c9 100644
--- a/Userland/Utilities/expr.cpp
+++ b/Userland/Utilities/expr.cpp
@@ -441,14 +441,17 @@ private:
 
     void ensure_regex() const
     {
-        if (!m_compiled_regex)
-            m_compiled_regex = make<regex::Regex<PosixExtended>>(m_pos_or_chars->string());
+        if (!m_compiled_regex) {
+            m_compiled_regex = make<regex::Regex<PosixBasic>>(m_pos_or_chars->string());
+            if (m_compiled_regex->parser_result.error != regex::Error::NoError)
+                fail("Regex error: {}", regex::get_error_string(m_compiled_regex->parser_result.error));
+        }
     }
 
     StringOperation m_op { StringOperation::Substring };
     NonnullOwnPtr<Expression> m_str;
     OwnPtr<Expression> m_pos_or_chars, m_length;
-    mutable OwnPtr<regex::Regex<PosixExtended>> m_compiled_regex;
+    mutable OwnPtr<regex::Regex<PosixBasic>> m_compiled_regex;
 };
 
 NonnullOwnPtr<Expression> Expression::parse(Queue<StringView>& args, Precedence prec)