Fix compilation failures?

Author: lhecker

src/terminal/adapter/ut_adapter/TestHook.h

@@ -4,6 +4,7 @@ namespace TestHook
 {
     struct LayoutGuard
     {
+        LayoutGuard() = default;
         LayoutGuard(HKL layout, bool needsUnload) noexcept;
         ~LayoutGuard();
 

src/terminal/adapter/ut_adapter/inputTest.cpp

@@ -628,7 +628,17 @@ void InputTest::TerminalInputNullKeyTests()
 {
     using namespace std::string_view_literals;
 
-    const auto layout = TestHook::SetTerminalInputKeyboardLayout(L"00000409"); // US English
+    TestHook::LayoutGuard layout;
+    try
+    {
+        layout = TestHook::SetTerminalInputKeyboardLayout(L"00000409"); // US English
+    }
+    catch (...)
+    {
+        Log::Result(TestResults::Result::Skipped);
+        return;
+    }
+
     unsigned int uiKeystate = LEFT_CTRL_PRESSED;
 
     TerminalInput input;

src/terminal/adapter/ut_adapter/kittyKeyboardProtocol.cpp

@@ -252,10 +252,29 @@ extern "C" HRESULT __declspec(dllexport) __cdecl KittyKeyTestDataSource(IDataSou
 
 class KittyKeyboardProtocolTests
 {
-    TestHook::LayoutGuard layout = TestHook::SetTerminalInputKeyboardLayout(L"0001040c"); // French (Standard, AZERTY)
+    TestHook::LayoutGuard layout;
 
     TEST_CLASS(KittyKeyboardProtocolTests);
 
+    TEST_CLASS_SETUP(ClassSetup)
+    {
+        try
+        {
+            layout = TestHook::SetTerminalInputKeyboardLayout(L"0001040c"); // French (Standard, AZERTY)
+        }
+        catch (...)
+        {
+            Log::Result(TestResults::Result::Skipped);
+        }
+        return true;
+    }
+
+    TEST_CLASS_CLEANUP(ClassCleanup)
+    {
+        layout = {};
+        return true;
+    }
+
     TEST_METHOD(KeyPressTests)
     {
         BEGIN_TEST_METHOD_PROPERTIES()

src/terminal/input/TestHook.cpp

@@ -0,0 +1,14 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+#include "precomp.h"
+
+// This default no-op implementation lives in its own .obj so that the linker
+// can skip it when a test DLL supplies its own definition. The classic linking
+// model only pulls in .obj files from a .lib if they resolve an otherwise
+// unresolved symbol - and nothing else in the test DLL refers to this file.
+// See: https://devblogs.microsoft.com/oldnewthing/20250416-00/?p=111077
+extern "C" HKL TestHook_TerminalInput_KeyboardLayout()
+{
+    return nullptr;
+}

src/terminal/input/lib/terminalinput.vcxproj

@@ -13,6 +13,7 @@
   <ItemGroup>
     <ClCompile Include="..\mouseInput.cpp" />
     <ClCompile Include="..\terminalInput.cpp" />
+    <ClCompile Include="..\TestHook.cpp" />
     <ClCompile Include="..\precomp.cpp">
       <PrecompiledHeader>Create</PrecompiledHeader>
     </ClCompile>

src/terminal/input/sources.inc

@@ -30,6 +30,7 @@ PRECOMPILED_INCLUDE     = ..\precomp.h
 SOURCES= \
     ..\terminalInput.cpp \
     ..\mouseInput.cpp \
+    ..\TestHook.cpp \
 
 INCLUDES = \
     $(INCLUDES); \

src/terminal/input/terminalInput.cpp

@@ -1497,15 +1497,10 @@ void TerminalInput::KeyboardHelper::init() noexcept
     }
 }
 
-#pragma comment(linker, "/alternatename:TestHook_TerminalInput_KeyboardLayout=TestHook_TerminalInput_KeyboardLayout_Default")
+// The default no-op implementation lives in TestHook.cpp (its own .obj) so the
+// linker can skip it when a test DLL supplies its own definition.
 extern "C" HKL TestHook_TerminalInput_KeyboardLayout();
 
-// Thanks to LTCG this should get inlined in Release builds and the test branch removed.
-extern "C" HKL TestHook_TerminalInput_KeyboardLayout_Default()
-{
-    return nullptr;
-}
-
 void TerminalInput::KeyboardHelper::initSlow() noexcept
 {
     if (const auto hkl = TestHook_TerminalInput_KeyboardLayout())