[WinSDK] Modularize <guiddef.h>

This fixes modularization errors that arise when importing a C++ header that contains `#include <guiddef.h>`, which might hijack this header from the WinSDK module where it belongs.

Author: egorzhdan

Runtimes/Overlay/Windows/clang/CMakeLists.txt

@@ -19,6 +19,12 @@ roots:
       - name: module.modulemap
         type: file
         external-contents: "@CMAKE_CURRENT_SOURCE_DIR@/winsdk.modulemap"
+  - name: "@WindowsSdkDir@/Include/@WindowsSDKVersion@/shared"
+    type: directory
+    contents:
+      - name: module.modulemap
+        type: file
+        external-contents: "@CMAKE_CURRENT_SOURCE_DIR@/winsdk_shared.modulemap"
   - name: "@UniversalCRTSdkDir@/Include/@UCRTVersion@/ucrt"
     type: directory
     contents:
@@ -48,4 +54,5 @@ install(FILES
   vcruntime.apinotes
   vcruntime.modulemap
   winsdk.modulemap
+  winsdk_shared.modulemap
   DESTINATION ${CMAKE_INSTALL_DATAROOTDIR})

Runtimes/Resync.cmake

@@ -159,6 +159,7 @@ copy_files(public/Platform Overlay/Windows/clang
   FILES
     ucrt.modulemap
     winsdk.modulemap
+    winsdk_shared.modulemap
     vcruntime.modulemap
     vcruntime.apinotes)
 

lib/ClangImporter/ClangIncludePaths.cpp

@@ -493,6 +493,17 @@ void GetWindowsFileMappings(
     if (!AuxiliaryFile.empty())
       fileMapping.redirectedFiles.emplace_back(std::string(WinSDKInjection),
                                                AuxiliaryFile);
+
+    if (WindowsSDK.MajorVersion > 8) {
+      llvm::sys::path::remove_filename(WinSDKInjection);
+      llvm::sys::path::remove_filename(WinSDKInjection);
+      llvm::sys::path::append(WinSDKInjection, "shared", "module.modulemap");
+      AuxiliaryFile = GetPlatformAuxiliaryFile(
+          "windows", "winsdk_shared.modulemap", SearchPathOpts);
+      if (!AuxiliaryFile.empty())
+        fileMapping.redirectedFiles.emplace_back(std::string(WinSDKInjection),
+                                                 AuxiliaryFile);
+    }
   }
 
   struct {

stdlib/cmake/WindowsVFS.yaml.in

@@ -9,6 +9,12 @@ roots:
       - name: module.modulemap
         type: file
         external-contents: "@PROJECT_SOURCE_DIR@\\public\\Platform\\winsdk.modulemap"
+  - name: "@UniversalCRTSdkDir@\\Include\\@UCRTVersion@\\shared"
+    type: directory
+    contents:
+      - name: module.modulemap
+        type: file
+        external-contents: "@PROJECT_SOURCE_DIR@\\public\\Platform\\winsdk_shared.modulemap"
   - name: "@UniversalCRTSdkDir@\\Include\\@UCRTVersion@\\ucrt"
     type: directory
     contents:

stdlib/public/Platform/CMakeLists.txt

@@ -468,6 +468,7 @@ if(WINDOWS IN_LIST SWIFT_SDKS)
       vcruntime.apinotes
       vcruntime.modulemap
       winsdk.modulemap
+      winsdk_shared.modulemap
     DESTINATION "share"
     COMPONENT sdk-overlay)
 endif()

stdlib/public/Platform/winsdk_shared.modulemap

@@ -0,0 +1,16 @@
+//===--- WinSDK_Shared.modulemap ------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+module _GUID {
+  header "guiddef.h"
+  export *
+}

stdlib/public/Windows/WinSDK.swift

@@ -11,6 +11,9 @@
 //===----------------------------------------------------------------------===//
 
 @_exported import ucrt
+#if canImport(_GUID)
+@_exported import _GUID
+#endif
 @_exported import WinSDK // Clang module
 
 // WinBase.h

test/stdlib/WinSDK_GUID.swift

@@ -0,0 +1,9 @@
+// RUN: %target-build-swift %s
+// REQUIRES: OS=windows-msvc
+
+// Make sure that importing WinSDK brings in the GUID type, which is declared in
+// /shared and not in /um.
+
+import WinSDK
+
+public func usesGUID(_ x: GUID) {}