[libcxx-commits] [libcxx] [libc++][C++03] Cherry-pick #129348 (PR #162821)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 updated https://github.com/llvm/llvm-project/pull/162821

>From fe315c848a015791e860a740f961d5a220a1e62c Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Fri, 10 Oct 2025 12:15:10 +0200
Subject: [PATCH] [libc++][C++03] Cherry-pick #129348

---
 libcxx/include/__cxx03/regex                         | 2 +-
 libcxx/test/std/re/re.alg/re.alg.match/ecma.pass.cpp | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/libcxx/include/__cxx03/regex b/libcxx/include/__cxx03/regex
index b96d59d3a252a..f4e662d283cb9 100644
--- a/libcxx/include/__cxx03/regex
+++ b/libcxx/include/__cxx03/regex
@@ -3911,7 +3911,7 @@ _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 799a362425ad5..0184a3835fb0d 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
@@ -7,8 +7,6 @@
 //===----------------------------------------------------------------------===//
 //
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
 // <regex>
 
 // template <class BidirectionalIterator, class Allocator, class charT, class traits>