[libcxx-commits] [libcxx] [regex] fix uncaught exception when string is like "\\_" (PR #129348)

[via libcxx-commits]

https://github.com/Zhenhang1213 updated https://github.com/llvm/llvm-project/pull/129348

>From 7a135297a7e7e593a342bc9d52ab94f243facfa4 Mon Sep 17 00:00:00 2001
From: Austin <zhenhangwang at huawei.com>
Date: Sat, 1 Mar 2025 10:37:20 +0800
Subject: [PATCH] [regex] fix uncaught exception when string is like "\\_"

fixes #129062
---
 libcxx/include/regex                              |  2 +-
 .../test/std/re/re.alg/re.alg.match/ecma.pass.cpp | 15 +++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/libcxx/include/regex b/libcxx/include/regex
index 36ea55ce30921..6916f91628821 100644
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -3954,7 +3954,7 @@ _ForwardIterator basic_regex<_CharT, _Traits>::__parse_character_escape(
       ++__first;
       break;
     default:
-      if (*__first != '_' && !__traits_.isctype(*__first, ctype_base::alnum)) {
+      if (!__traits_.isctype(*__first, ctype_base::alnum)) {
         if (__str)
           *__str = *__first;
         else
diff --git a/libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp b/libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp
index 4face8ba02bbe..6d1a183dbc839 100644
--- a/libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp
+++ b/libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp
@@ -669,6 +669,21 @@ int main(int, char**)
         assert(m.position(0) == 0);
         assert(m.str(0) == s);
     }
+    {
+        std::cmatch m;
+        const char s[] = "$_se";
+        assert(std::regex_match(s, m, std::regex("\\$\\_se")));
+        assert(m.size() == 1);
+        assert(!m.prefix().matched);
+        assert(m.prefix().first == s);
+        assert(m.prefix().second == m[0].first);
+        assert(!m.suffix().matched);
+        assert(m.suffix().first == m[0].second);
+        assert(m.suffix().second == s + std::char_traits<char>::length(s));
+        assert(m.length(0) >= 0 && static_cast<size_t>(m.length(0)) == std::char_traits<char>::length(s));
+        assert(m.position(0) == 0);
+        assert(m.str(0) == s);
+    }
 
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
     {