Merge branch 'win32-clear-com' into 'main'

GWin32: Add g_win32_com_clear()

See merge request GNOME/glib!4392

glib/gwin32.h

@@ -43,6 +43,11 @@ G_BEGIN_DECLS
 
 #ifdef G_OS_WIN32
 
+/* needed include for C++ builds; including this in C mode will cause havoc of type conflicts */
+#ifdef __cplusplus
+#include <unknwn.h>
+#endif
+
 /*
  * To get prototypes for the following POSIXish functions, you have to
  * include the indicated non-POSIX headers. The functions are defined
@@ -135,8 +140,60 @@ gboolean g_win32_check_windows_version (const gint major,
                                         const gint spver,
                                         const GWin32OSType os_type);
 
+/**
+ * g_win32_clear_com:
+ * @com_obj: (not optional) (nullable): Pointer to COM object pointer to release and clear
+ *
+ * Releases the referenced COM object, and clears its pointer to `NULL`.
+ *
+ * The @com_obj pointer must not be `NULL`.
+ *
+ * If @com_obj references a `NULL` COM  object, this function is a no-op.
+ *
+ * This is equivalent to `g_clear_object()` for dealing with
+ * Windows COM objects.
+ *
+ * Since: 2.84
+ */
+
+#ifndef __cplusplus
+
+#define g_win32_clear_com(com_obj) \
+G_STMT_START {\
+  IUnknown **unknown_com_obj = (IUnknown **)(com_obj); \
+  \
+  if (*unknown_com_obj) \
+    { \
+      (*unknown_com_obj)->lpVtbl->Release (*unknown_com_obj); \
+      *unknown_com_obj = NULL; \
+    } \
+} G_STMT_END \
+GLIB_AVAILABLE_MACRO_IN_2_84
+
+#endif
+
 G_END_DECLS
 
+#ifdef __cplusplus
+/*
+ * There are COM objects that only have C++-style definitions, such as DirectWrite
+ * from the Windows SDK (albeit a C interface is provided for the mingw-w64 toolchain),
+ * so we need to have a C++ version for this
+ */
+template <typename com_interface>
+static inline void
+g_win32_clear_com (com_interface **com_obj)
+{
+  IUnknown **unknown_com_obj = reinterpret_cast<IUnknown **>(com_obj);
+
+  if (*unknown_com_obj != NULL)
+    {
+      (*unknown_com_obj)->Release ();
+      *unknown_com_obj = NULL;
+    }
+}
+#endif
+
 #endif	 /* G_PLATFORM_WIN32 */
 
 #endif /* __G_WIN32_H__ */

glib/tests/cxx.cpp

@@ -19,6 +19,10 @@
 
 #include <glib.h>
 
+#ifdef G_OS_WIN32
+#include <wincodec.h>
+#endif
+
 #if !defined (G_CXX_STD_VERSION) || !defined (G_CXX_STD_CHECK_VERSION)
 #error G_CXX_STD_VERSION is not defined
 #endif
@@ -532,6 +536,31 @@ test_string_free (void)
   g_free (data);
 }
 
+#ifdef G_OS_WIN32
+static void
+test_clear_com (void)
+{
+  IWICImagingFactory *tmp;
+  IWICImagingFactory *o =  NULL;
+
+  CoInitialize (NULL);
+  g_win32_clear_com (&o);
+  g_assert_null (o);
+  g_assert_true (SUCCEEDED (CoCreateInstance (CLSID_WICImagingFactory, NULL, CLSCTX_INPROC_SERVER, IID_IWICImagingFactory, (void **)&tmp)));
+  g_assert_nonnull (tmp);
+  tmp->QueryInterface (IID_IWICImagingFactory, (void **)&o); /* IWICImagingFactory::QueryInterface increments tmp's refcount */
+  g_assert_nonnull (o);
+  g_assert_cmpint (tmp->AddRef (), ==, 3); /* tmp's refcount incremented again */
+  g_win32_clear_com (&o);  /* tmp's refcount gets decremented */
+  g_assert_null (o);
+  g_assert_cmpint (tmp->Release (), ==, 1);  /* tmp's refcount gets decremented, again */
+  g_win32_clear_com (&tmp);
+  g_assert_null (tmp);
+
+  CoUninitialize ();
+}
+#endif
+
 int
 main (int argc, char *argv[])
 {
@@ -566,5 +595,8 @@ main (int argc, char *argv[])
   g_test_add_func ("/C++/string-append", test_string_append);
   g_test_add_func ("/C++/string-free", test_string_free);
 
+#ifdef G_OS_WIN32
+  g_test_add_func ("/C++/test_clear_com", test_clear_com);
+#endif
   return g_test_run ();
 }

glib/tests/meson.build

@@ -209,6 +209,7 @@ if have_cxx
     'cxx' : {
       'source' : ['cxx.cpp'],
       'suite': ['cpp'],
+      'dependencies' : [wincodecs],
     }
   }
 
@@ -218,6 +219,7 @@ if have_cxx
         'source' : ['cxx.cpp'],
         'suite' : ['cpp'],
         'cpp_args' : [arg, '-D_G_EXPECTED_CXX_STANDARD="@0@"'.format(std)],
+        'dependencies' : [wincodecs],
       },
     }
   endforeach
@@ -246,7 +248,9 @@ if host_machine.system() == 'windows'
     }
   endif
   glib_tests += {
-    'win32' : {},
+    'win32' : {
+      'dependencies' : [wincodecs],
+    },
   }
 else
   glib_tests += {

glib/tests/win32.c

@@ -28,6 +28,9 @@
 #include <stdio.h>
 #include <windows.h>
 
+#define COBJMACROS
+#include <wincodec.h>
+
 static char *argv0 = NULL;
 
 #include "../gwin32-private.c"
@@ -154,6 +157,29 @@ veh_debugger (int argc, char *argv[])
   g_fprintf (stderr, "Debugger invoked, attaching to %lu and signalling %" G_GUINTPTR_FORMAT, pid, event);
 }
 
+static void
+test_clear_com (void)
+{
+  IWICImagingFactory *o = NULL;
+  IWICImagingFactory *tmp;
+
+  CoInitialize (NULL);
+  g_win32_clear_com (&o);
+  g_assert_null (o);
+  g_assert_true (SUCCEEDED (CoCreateInstance (&CLSID_WICImagingFactory, NULL, CLSCTX_INPROC_SERVER, &IID_IWICImagingFactory, (void **)&tmp)));
+  g_assert_nonnull (tmp);
+  IWICImagingFactory_QueryInterface (tmp, &IID_IWICImagingFactory, (void **)&o); /* IWICImagingFactory_QueryInterface increments tmp's refcount */
+  g_assert_nonnull (o);
+  g_assert_cmpint (IWICImagingFactory_AddRef (tmp), ==, 3); /* tmp's refcount incremented, again */
+  g_win32_clear_com (&o);  /* tmp's refcount decrements */
+  g_assert_null (o);
+  g_assert_cmpint (IWICImagingFactory_Release (tmp), ==, 1);   /* tmp's refcount decrements, again */
+  g_win32_clear_com (&tmp);
+  g_assert_null (tmp);
+
+  CoUninitialize ();
+}
+
 int
 main (int   argc,
       char *argv[])
@@ -177,6 +203,7 @@ main (int   argc,
   g_test_add_func ("/win32/subprocess/debuggee", test_veh_debuggee);
   g_test_add_func ("/win32/subprocess/access_violation", test_access_violation);
   g_test_add_func ("/win32/subprocess/illegal_instruction", test_illegal_instruction);
+  g_test_add_func ("/win32/com/clear", test_clear_com);
 
   return g_test_run();
 }

meson.build

@@ -2338,8 +2338,11 @@ endif
 
 if host_system == 'windows'
   winsock2 = cc.find_library('ws2_32')
+  # Used for g_win32_clear_com() tests...
+  wincodecs = cc.find_library('windowscodecs')
 else
   winsock2 = not_found
+  wincodecs = not_found
 endif
 
 selinux_dep = []