From 597a0c2d1e618ab3620361d90c67c3728e80d631 Mon Sep 17 00:00:00 2001
From: "Herman S." <429230+has207@users.noreply.github.com>
Date: Thu, 26 Mar 2026 21:25:28 +0900
Subject: [PATCH] [Xboxkrnl] Use towupper in RtlUpcaseUnicodeChar for
 portability

std::ctype<char16_t> is a non-standard extension that's not available
on all platforms. Neither this nor the original technically match the
Windows kernel's fixed Unicode table approach and can produce different
results based on system locale.
---
 src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc b/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
index c1df05979..67bfa3322 100644
--- a/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
+++ b/src/xenia/kernel/xboxkrnl/xboxkrnl_rtl.cc
@@ -229,8 +229,8 @@ void RtlInitAnsiString_entry(pointer_t<X_ANSI_STRING> destination,
 DECLARE_XBOXKRNL_EXPORT1(RtlInitAnsiString, kNone, kImplemented);
 // https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-rtlupcaseunicodechar
 dword_result_t RtlUpcaseUnicodeChar_entry(dword_t SourceCharacter) {
-  return std::use_facet<std::ctype<char16_t>>(std::locale())
-      .toupper(SourceCharacter);
+  return static_cast<uint32_t>(std::towupper(
+      static_cast<wint_t>(static_cast<uint32_t>(SourceCharacter))));
 }
 DECLARE_XBOXKRNL_EXPORT1(RtlUpcaseUnicodeChar, kNone, kImplemented);