From db8d2bc1c93bf7730d106c2b2b625f6fd51752cc Mon Sep 17 00:00:00 2001
From: MarcZX10 <67475268+MarcZX10@users.noreply.github.com>
Date: Sun, 25 Oct 2026 11:31:48 +0000
Subject: [PATCH 1/2] fix(libSceConvertKeycode): look up keyboard types without
 signed overflow

LookUp subtracted the first mapped type, 16, from the UserService keyboard type in 32 bits, which overflows for keyboard types below INT32_MIN + 16; sceConvertKeycodeGetImeKeyboardType passes the type it read from UserService. Compute the index in 64 bits. Every type still maps to the same IME keyboard type, and types outside the table still map to 0.
---
 core/libs/prx/libSceConvertKeycode/ImeKeyboardType.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/libs/prx/libSceConvertKeycode/ImeKeyboardType.hpp b/core/libs/prx/libSceConvertKeycode/ImeKeyboardType.hpp
index 4ace3c252c..ec7e041937 100644
--- a/core/libs/prx/libSceConvertKeycode/ImeKeyboardType.hpp
+++ b/core/libs/prx/libSceConvertKeycode/ImeKeyboardType.hpp
@@ -35,7 +35,7 @@ constexpr std::uint32_t LookUp(std::int32_t keyboardType, std::int32_t japaneseV
         constexpr std::uint32_t traditionalChinese[] = {26, 27, 28, 29, 39};
         return traditionalChineseVariant >= 0 && traditionalChineseVariant < 5 ? traditionalChinese[traditionalChineseVariant] : 0;
     }
-    const std::int32_t index = keyboardType - kFirstMappedType;
+    const std::int64_t index = std::int64_t{keyboardType} - kFirstMappedType;
     return index >= 0 && index < kMappedTypeCount ? kImeTypeByKeyboardType[index] : 0;
 }
 

From 89af2b225e64b336bf06af798fd4024e053a8c3e Mon Sep 17 00:00:00 2001
From: MarcZX10 <67475268+MarcZX10@users.noreply.github.com>
Date: Sun, 25 Oct 2026 11:31:48 +0000
Subject: [PATCH 2/2] test(libSceConvertKeycode): check the keyboard type
 lookup at both int32 limits at compile time

LookUp is constexpr, so static_assert evaluates it for INT32_MIN and INT32_MAX in a constant expression, where signed overflow is an error. With the previous 32-bit subtraction the test file no longer compiles ('overflow in constant expression'); the existing runtime case for 0x80000000 only showed the overflow under UBSan.
---
 core/libs/tests/GuestConvertKeycode.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/core/libs/tests/GuestConvertKeycode.cpp b/core/libs/tests/GuestConvertKeycode.cpp
index 8bf7b815b0..d2d3cb463f 100644
--- a/core/libs/tests/GuestConvertKeycode.cpp
+++ b/core/libs/tests/GuestConvertKeycode.cpp
@@ -15,6 +15,9 @@
 
 static void Require(bool value) { if (!value) std::abort(); }
 
+static_assert(ImeKeyboardType::LookUp(INT32_MIN, 0, 0) == 0);
+static_assert(ImeKeyboardType::LookUp(INT32_MAX, 0, 0) == 0);
+
 static void SetLanguage(const char* value) {
 #ifdef _WIN32
     Require(_putenv_s("ANYPS5_LANGUAGE", value != nullptr ? value : "") == 0);