From 72e36c958e6dfdd216a0ecbcad1ee24f24813da0 Mon Sep 17 00:00:00 2001
From: Alvin Wong <alvin@alvinhc.com>
Date: Fri, 21 Oct 2022 21:13:52 +0800
Subject: [PATCH 1/2] Enable classic COM on mingw-w64

Mingw-w64 does not use `__declspec(uuid(x))` but has its own way of
supporting `__uuidof` by defining UUIDs with a special macro
`__CRT_UUID_DECL`, which does actually work here.
---
 strings/base_macros.h |  8 ++++++++
 strings/base_meta.h   | 16 +++-------------
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/strings/base_macros.h b/strings/base_macros.h
index c4ec6645b..a7d757fad 100644
--- a/strings/base_macros.h
+++ b/strings/base_macros.h
@@ -59,6 +59,14 @@
 #define WINRT_IMPL_NOVTABLE
 #endif
 
+#if defined(__clang__)
+#define WINRT_IMPL_HAS_DECLSPEC_UUID __has_declspec_attribute(uuid)
+#elif defined(_MSC_VER)
+#define WINRT_IMPL_HAS_DECLSPEC_UUID 1
+#else
+#define WINRT_IMPL_HAS_DECLSPEC_UUID 0
+#endif
+
 #ifdef __IUnknown_INTERFACE_DEFINED__
 #define WINRT_IMPL_IUNKNOWN_DEFINED
 #else
diff --git a/strings/base_meta.h b/strings/base_meta.h
index 061a9f587..72c98c27a 100644
--- a/strings/base_meta.h
+++ b/strings/base_meta.h
@@ -120,27 +120,17 @@ namespace winrt::impl
     template <typename T>
     struct classic_com_guid_error
     {
-#ifdef __clang__
-#if !__has_declspec_attribute(uuid)
+#if !defined(__MINGW32__) && defined(__clang__) && !WINRT_IMPL_HAS_DECLSPEC_UUID
         static_assert(std::is_void_v<T> /* dependent_false */, "To use classic COM interfaces, you must compile with -fms-extensions.");
-#endif
-
-#ifndef WINRT_IMPL_IUNKNOWN_DEFINED
+#elif !defined(WINRT_IMPL_IUNKNOWN_DEFINED)
         static_assert(std::is_void_v<T> /* dependent_false */, "To use classic COM interfaces, you must include <unknwn.h> before including C++/WinRT headers.");
-#endif
 #else // MSVC won't hit this struct, so we can safely assume everything that isn't Clang isn't supported
         static_assert(std::is_void_v<T> /* dependent_false */, "Classic COM interfaces are not supported with this compiler.");
 #endif
     };
 
     template <typename T>
-#ifdef __clang__
-#if __has_declspec_attribute(uuid) && defined(WINRT_IMPL_IUNKNOWN_DEFINED)
-    inline constexpr guid guid_v{ __uuidof(T) };
-#else
-    inline constexpr guid guid_v = classic_com_guid_error<T>::value;
-#endif
-#elif defined(_MSC_VER)
+#if defined(_MSC_VER) || ((WINRT_IMPL_HAS_DECLSPEC_UUID || defined(__MINGW32__)) && defined(WINRT_IMPL_IUNKNOWN_DEFINED))
     inline constexpr guid guid_v{ __uuidof(T) };
 #else
     inline constexpr guid guid_v = classic_com_guid_error<T>::value;

From 0c5d6e5ad6876db3d18a8f0f12ed7385d80cce4d Mon Sep 17 00:00:00 2001
From: Alvin Wong <alvin@alvinhc.com>
Date: Fri, 21 Oct 2022 21:40:37 +0800
Subject: [PATCH 2/2] Fix Clang-cl config

---
 strings/base_meta.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/strings/base_meta.h b/strings/base_meta.h
index 72c98c27a..54d41e61b 100644
--- a/strings/base_meta.h
+++ b/strings/base_meta.h
@@ -130,7 +130,7 @@ namespace winrt::impl
     };
 
     template <typename T>
-#if defined(_MSC_VER) || ((WINRT_IMPL_HAS_DECLSPEC_UUID || defined(__MINGW32__)) && defined(WINRT_IMPL_IUNKNOWN_DEFINED))
+#if (defined(_MSC_VER) && !defined(__clang__)) || ((WINRT_IMPL_HAS_DECLSPEC_UUID || defined(__MINGW32__)) && defined(WINRT_IMPL_IUNKNOWN_DEFINED))
     inline constexpr guid guid_v{ __uuidof(T) };
 #else
     inline constexpr guid guid_v = classic_com_guid_error<T>::value;