Common (Windows): allows COM be used in C sources

CMakeLists.txt

@@ -1033,7 +1033,7 @@ elseif(WIN32)
         src/common/impl/debug_windows.c
         src/common/impl/kmod_windows.c
         src/common/windows/getline.c
-        src/common/windows/com.cpp
+        src/common/windows/com.c
         src/common/windows/registry.c
         src/common/windows/unicode.c
         src/common/windows/variant.cpp

src/common/windows/com.c

@@ -1,4 +1,4 @@
-#include "com.hpp"
+#include "com.h"
 
 #include <roapi.h>
 

src/common/windows/com.h

@@ -1,23 +1,23 @@
 #pragma once
 
-#ifdef __cplusplus
-
-    #include "common/attributes.h"
-    #include <unknwn.h>
+#include "common/attributes.h"
+#include <assert.h>
+#include <unknwn.h>
 
 // Initialize COM & WinRT
 const char* ffInitCom(void);
 
 static inline void ffReleaseComObject(void* ppUnknown) {
+    assert(ppUnknown);
     IUnknown* pUnknown = *(IUnknown**) ppUnknown;
     if (pUnknown) {
+#ifdef __cplusplus
         pUnknown->Release();
+#else
+        pUnknown->lpVtbl->Release(pUnknown);
+#endif
+        *(IUnknown**) ppUnknown = NULL;
     }
 }
 
-    #define FF_AUTO_RELEASE_COM_OBJECT FF_A_CLEANUP(ffReleaseComObject)
-
-#else
-    // Win32 COM headers requires C++ compiler
-    #error Must be included in C++ source file
-#endif
+#define FF_AUTO_RELEASE_COM_OBJECT FF_A_CLEANUP(ffReleaseComObject)

src/detection/camera/camera_windows.cpp

@@ -1,8 +1,8 @@
 extern "C" {
 #include "camera.h"
 #include "common/library.h"
+#include "common/windows/com.h"
 }
-#include "common/windows/com.hpp"
 #include "common/windows/unicode.hpp"
 #include "common/windows/util.hpp"
 

src/detection/media/media_windows.cpp

@@ -2,6 +2,7 @@ extern "C" {
 #include "media.h"
 #include "common/time.h"
 #include "common/windows/unicode.h"
+#include "common/windows/com.h"
 }
 
 #if FF_HAVE_WINRT
@@ -15,8 +16,6 @@ extern "C" {
     #include <winrt/Windows.Media.Control.h>
     #include <winrt/Windows.Storage.Streams.h>
 
-    #include "common/windows/com.hpp"
-
     #define FF_BIND_FRONT(method, pobject) std::bind_front(&std::remove_cvref_t<decltype(*(pobject))>::method, (pobject))
 
 using winrt::impl::abi_t;

src/detection/sound/sound_windows.cpp

@@ -1,8 +1,8 @@
 extern "C" {
 #include "sound.h"
+#include "common/windows/com.h"
 }
 #include "common/windows/unicode.hpp"
-#include "common/windows/com.hpp"
 #include "common/windows/variant.hpp"
 
 #include <initguid.h>