YexuanXiao · YexuanXiao · Apr 19, 2026
diff --git a/cppwinrt/code_writers.h b/cppwinrt/code_writers.h
@@ -203,9 +203,20 @@ namespace cppwinrt
         return { w, write_close_namespace };
     }
 
+    [[nodiscard]] static finish_with wrap_impl_namespace_without_export(writer& w)
+    {
+        auto format = R"(extern "C++" namespace winrt::impl
+{
+)";
+
+        w.write(format);
+
+        return { w, write_close_namespace };
+    }
+
     [[nodiscard]] static finish_with wrap_std_namespace(writer& w)
     {
-        w.write(R"(WINRT_EXPORT namespace std
+        w.write(R"(extern "C++" namespace std
 {
 )");
 

diff --git a/cppwinrt/file_writers.h b/cppwinrt/file_writers.h
@@ -44,6 +44,11 @@ namespace cppwinrt
         {
             auto wrap_file_guard = wrap_open_file_guard(w, "BASE");
 
+            if (settings.modules)
+            {
+                w.write("#ifndef WINRT_CONSUME_MODULE\n");
+            }
+
             {
                 // In module builds, generated projection headers must be "module-aware":
                 // When `WINRT_MODULE` is defined (inside a module interface unit), suppress textual includes so the
@@ -85,6 +90,11 @@ namespace cppwinrt
             w.write(strings::base_coroutine_threadpool);
             w.write(strings::base_natvis);
             w.write(strings::base_version);
+
+            if (settings.modules)
+            {
+                w.write("#endif\n");
+            }
         }
         w.flush_to_file(settings.output_folder + "winrt/base.h");
     }
@@ -142,7 +152,7 @@ namespace cppwinrt
             w.write_each<write_forward>(members.contracts);
         }
         {
-            auto wrap_impl = wrap_impl_namespace(w);
+            auto wrap_impl = wrap_impl_namespace_without_export(w);
             w.write_each<write_category>(members.interfaces, "interface_category");
             w.write_each<write_category>(members.classes, "class_category");
             w.write_each<write_category>(members.enums, "enum_category");
@@ -165,9 +175,12 @@ namespace cppwinrt
             w.write_each<write_default_interface>(members.classes);
             w.write_each<write_interface_abi>(members.interfaces);
             w.write_each<write_delegate_abi>(members.delegates);
-            w.write_each<write_consume>(members.interfaces);
             w.write_each<write_struct_abi>(members.structs);
         }
+        {
+            auto wrap_impl = wrap_impl_namespace(w);
+            w.write_each<write_consume>(members.interfaces);
+        }
 
         if (settings.modules)
         {
@@ -319,66 +332,38 @@ namespace cppwinrt
 #undef GetCurrentTime
 #endif
 
+// Include in advance so that all of numerics's dependencies can be in the global module fragment
+#include <stdexcept>
+#include <limits>
+#if __has_include(<directxmath.h>) && __has_include(<windowsnumerics.impl.h>)
+#include <directxmath.h>
+#endif
+
 export module winrt.base;
 
 // Module dependencies:
 //   - std
-//   - winrt.numerics (re-exported when available)
 
 import std;
-export import winrt.numerics;
-
-#if __has_include(<windowsnumerics.impl.h>)
-#define WINRT_IMPL_NUMERICS
-#endif
-
-#include "winrt/base.h"
-)");
 
-        w.flush_to_file(settings.output_folder + "winrt/winrt.base.ixx");
-    }
-
-    static void write_numerics_ixx()
-    {
-        // Emits $(out)\winrt\winrt.numerics.ixx  (export module winrt.numerics;)
-        // <windowsnumerics.impl.h> pulls in large, legacy headers that are hard to control and can trigger module
-        // diagnostics when textually included in a module purview.
-        // If the header does not exist, then the module exports nothing. To speed up module scanning, modules
-        // can't be controlled by preprocessor directives. Therefore, winrt.base cannot conditionally import it.
-        // In header builds we preserve the historical behavior (base headers include it), but in module builds we
-        // centralize it in this single module and have `winrt.base` re-export it.
-        // MSVC warns (C5244) when encountering textual includes inside a module purview; suppress for this file.
-        writer w;
-        write_preamble(w);
-        write_module_global_fragment(w);
-
-        w.write(R"(
-export module winrt.numerics;
-
-// Module dependencies:
-//   - (none)
-
-#if __has_include(<windowsnumerics.impl.h>)
-#ifdef _MSC_VER
-#pragma warning(push)
+// An MSVC warning whose cause cannot be analyzed
+// warning C5244: '#include <windowsnumerics.impl.h>' in the purview of module 'winrt.base' appears erroneous.  Consider moving that directive before the module declaration, or replace the textual inclusion with 'import <windowsnumerics.impl.h>;'.
 #pragma warning(disable : 5244)
-#endif
-#include <directxmath.h>
 
+#if __has_include(<windowsnumerics.impl.h>)
 #define _WINDOWS_NUMERICS_NAMESPACE_ winrt::Windows::Foundation::Numerics
-#define _WINDOWS_NUMERICS_BEGIN_NAMESPACE_ export extern "C++" namespace winrt::Windows::Foundation::Numerics
+#define _WINDOWS_NUMERICS_BEGIN_NAMESPACE_ export extern "C++" namespace _WINDOWS_NUMERICS_NAMESPACE_
 #define _WINDOWS_NUMERICS_END_NAMESPACE_
 #include <windowsnumerics.impl.h>
 #undef _WINDOWS_NUMERICS_NAMESPACE_
 #undef _WINDOWS_NUMERICS_BEGIN_NAMESPACE_
 #undef _WINDOWS_NUMERICS_END_NAMESPACE_
-#ifdef _MSC_VER
-#pragma warning(pop)
-#endif
 #endif
+
+#include "winrt/base.h"
 )");
 
-        w.flush_to_file(settings.output_folder + "winrt/winrt.numerics.ixx");
+        w.flush_to_file(settings.output_folder + "winrt/winrt.base.ixx");
     }
 
     static void write_namespace_ixx(std::string_view const& ns, std::vector<std::string> const& imports)
@@ -581,7 +566,7 @@ export import winrt.base;
         w.type_namespace = ns;
 
         {
-            auto wrap_impl = wrap_impl_namespace(w);
+            auto wrap_impl = wrap_impl_namespace_without_export(w);
             w.write_each<write_consume_definitions>(members.interfaces);
             w.param_names = true;
             w.write_each<write_delegate_implementation>(members.delegates);

diff --git a/cppwinrt/main.cpp b/cppwinrt/main.cpp
@@ -622,7 +622,6 @@ R"(  local               Local ^%WinDir^%\System32\WinMetadata folder
 
             if (settings.modules)
             {
-                write_numerics_ixx();
                 write_base_ixx();
             }
 

diff --git a/cppwinrt/type_writers.h b/cppwinrt/type_writers.h
@@ -334,13 +334,7 @@ namespace cppwinrt
             {
                 if (ns == "Windows.Foundation.Numerics")
                 {
-                    if (name == "Matrix3x2") { name = "float3x2"; }
-                    else if (name == "Matrix4x4") { name = "float4x4"; }
-                    else if (name == "Plane") { name = "plane"; }
-                    else if (name == "Quaternion") { name = "quaternion"; }
-                    else if (name == "Vector2") { name = "float2"; }
-                    else if (name == "Vector3") { name = "float3"; }
-                    else if (name == "Vector4") { name = "float4"; }
+                    transform_special_numeric_type(name);
 
                     write("winrt::@::%", ns, name);
                 }

diff --git a/strings/base_abi.h b/strings/base_abi.h
@@ -1,5 +1,5 @@
 
-WINRT_EXPORT namespace winrt::impl
+extern "C++" namespace winrt::impl
 {
     template <> struct abi<Windows::Foundation::IUnknown>
     {
@@ -11,7 +11,7 @@ WINRT_EXPORT namespace winrt::impl
         };
     };
 
-    using unknown_abi = abi_t<Windows::Foundation::IUnknown>;
+    WINRT_EXPORT using unknown_abi = abi_t<Windows::Foundation::IUnknown>;
 
     template <> struct abi<Windows::Foundation::IInspectable>
     {
@@ -23,7 +23,7 @@ WINRT_EXPORT namespace winrt::impl
         };
     };
 
-    using inspectable_abi = abi_t<Windows::Foundation::IInspectable>;
+    WINRT_EXPORT using inspectable_abi = abi_t<Windows::Foundation::IInspectable>;
 
     template <> struct abi<Windows::Foundation::IActivationFactory>
     {
@@ -33,14 +33,14 @@ WINRT_EXPORT namespace winrt::impl
         };
     };
 
-    struct WINRT_IMPL_ABI_DECL IAgileObject : unknown_abi {};
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IAgileObject : unknown_abi {};
 
-    struct WINRT_IMPL_ABI_DECL IAgileReference : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IAgileReference : unknown_abi
     {
         virtual std::int32_t __stdcall Resolve(guid const& id, void** object) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IMarshal : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IMarshal : unknown_abi
     {
         virtual std::int32_t __stdcall GetUnmarshalClass(guid const& riid, void* pv, std::uint32_t dwDestContext, void* pvDestContext, std::uint32_t mshlflags, guid* pCid) noexcept = 0;
         virtual std::int32_t __stdcall GetMarshalSizeMax(guid const& riid, void* pv, std::uint32_t dwDestContext, void* pvDestContext, std::uint32_t mshlflags, std::uint32_t* pSize) noexcept = 0;
@@ -50,20 +50,20 @@ WINRT_EXPORT namespace winrt::impl
         virtual std::int32_t __stdcall DisconnectObject(std::uint32_t dwReserved) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IGlobalInterfaceTable : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IGlobalInterfaceTable : unknown_abi
     {
         virtual std::int32_t __stdcall RegisterInterfaceInGlobal(void* object, guid const& iid, std::uint32_t* cookie) noexcept = 0;
         virtual std::int32_t __stdcall RevokeInterfaceFromGlobal(std::uint32_t cookie) noexcept = 0;
         virtual std::int32_t __stdcall GetInterfaceFromGlobal(std::uint32_t cookie, guid const& iid, void** object) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IStaticLifetime : inspectable_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IStaticLifetime : inspectable_abi
     {
         virtual std::int32_t __stdcall unused() noexcept = 0;
         virtual std::int32_t __stdcall GetCollection(void** value) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IStaticLifetimeCollection : inspectable_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IStaticLifetimeCollection : inspectable_abi
     {
         virtual std::int32_t __stdcall Lookup(void*, void**) noexcept = 0;
         virtual std::int32_t __stdcall unused() noexcept = 0;
@@ -74,23 +74,23 @@ WINRT_EXPORT namespace winrt::impl
         virtual std::int32_t __stdcall unused4() noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IWeakReference : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IWeakReference : unknown_abi
     {
         virtual std::int32_t __stdcall Resolve(guid const& iid, void** objectReference) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IWeakReferenceSource : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IWeakReferenceSource : unknown_abi
     {
         virtual std::int32_t __stdcall GetWeakReference(IWeakReference** weakReference) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IRestrictedErrorInfo : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IRestrictedErrorInfo : unknown_abi
     {
         virtual std::int32_t __stdcall GetErrorDetails(bstr* description, std::int32_t* error, bstr* restrictedDescription, bstr* capabilitySid) noexcept = 0;
         virtual std::int32_t __stdcall GetReference(bstr* reference) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IErrorInfo : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IErrorInfo : unknown_abi
     {
         virtual std::int32_t __stdcall GetGUID(guid* value) noexcept = 0;
         virtual std::int32_t __stdcall GetSource(bstr* value) noexcept = 0;
@@ -99,35 +99,35 @@ WINRT_EXPORT namespace winrt::impl
         virtual std::int32_t __stdcall GetHelpContext(std::uint32_t* value) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL ILanguageExceptionErrorInfo2 : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL ILanguageExceptionErrorInfo2 : unknown_abi
     {
         virtual std::int32_t __stdcall GetLanguageException(void** exception) noexcept = 0;
         virtual std::int32_t __stdcall GetPreviousLanguageExceptionErrorInfo(ILanguageExceptionErrorInfo2** previous) noexcept = 0;
         virtual std::int32_t __stdcall CapturePropagationContext(void* exception) noexcept = 0;
         virtual std::int32_t __stdcall GetPropagationContextHead(ILanguageExceptionErrorInfo2** head) noexcept = 0;
     };
 
-    struct ICallbackWithNoReentrancyToApplicationSTA;
+    WINRT_EXPORT struct ICallbackWithNoReentrancyToApplicationSTA;
 
-    struct WINRT_IMPL_ABI_DECL IContextCallback : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IContextCallback : unknown_abi
     {
         virtual std::int32_t __stdcall ContextCallback(std::int32_t(__stdcall* callback)(com_callback_args*), com_callback_args* args, guid const& iid, int method, void* reserved) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IServerSecurity : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IServerSecurity : unknown_abi
     {
         virtual std::int32_t __stdcall QueryBlanket(std::uint32_t*, std::uint32_t*, wchar_t**, std::uint32_t*, std::uint32_t*, void**, std::uint32_t*) noexcept = 0;
         virtual std::int32_t __stdcall ImpersonateClient() noexcept = 0;
         virtual std::int32_t __stdcall RevertToSelf() noexcept = 0;
         virtual std::int32_t __stdcall IsImpersonating() noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IBufferByteAccess : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IBufferByteAccess : unknown_abi
     {
         virtual std::int32_t __stdcall Buffer(std::uint8_t** value) noexcept = 0;
     };
 
-    struct WINRT_IMPL_ABI_DECL IMemoryBufferByteAccess : unknown_abi
+    WINRT_EXPORT struct WINRT_IMPL_ABI_DECL IMemoryBufferByteAccess : unknown_abi
     {
         virtual std::int32_t __stdcall GetBuffer(std::uint8_t** value, std::uint32_t* capacity) noexcept = 0;
     };
-Original file line number
+Diff line change
@@ Expand Up / @@ -622,7 +622,6 @@ R"( local Local ^%WinDir^%\System32\WinMetadata folder @@
                 if (settings.modules)
                 {
-                    write_numerics_ixx();
                     write_base_ixx();
                 }
@@ Expand Down @@