[glib/glib-2-32] Fix g_clear_object macro with C++ compilers

[Xavier Claessens <xclaesse src gnome org>]

commit d92736ab032bb650b1d115042e2a0ff965175940
Author: Xavier Claessens <xavier claessens collabora co uk>
Date:   Wed Apr 25 15:02:25 2012 +0200

    Fix g_clear_object macro with C++ compilers
    
    In C++ it is invalid to cast a void* to void**.
    
    Also add a static check to ensure
    sizeof(*object_ptr) == sizeof (gpointer).
    This avoid common mistake of missing '&'
    in g_clear_object(&obj);
    
    https://bugzilla.gnome.org/show_bug.cgi?id=674634

 gobject/gobject.h |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gobject/gobject.h b/gobject/gobject.h
index 3572736..8c9e42a 100644
--- a/gobject/gobject.h
+++ b/gobject/gobject.h
@@ -563,10 +563,12 @@ G_STMT_START { \
 void    g_clear_object (volatile GObject **object_ptr);
 #define g_clear_object(object_ptr) \
   G_STMT_START {                                                             \
+    G_STATIC_ASSERT (sizeof *(object_ptr) == sizeof (gpointer));             \
     /* Only one access, please */                                            \
-    gpointer *_p = (gpointer) (object_ptr);                                  \
+    gpointer *_p = (gpointer *) (object_ptr);                                \
     gpointer _o;                                                             \
                                                                              \
+    (void) (0 ? (gpointer) *(object_ptr) : 0);                               \
     do                                                                       \
       _o = g_atomic_pointer_get (_p);                                        \
     while G_UNLIKELY (!g_atomic_pointer_compare_and_exchange (_p, _o, NULL));\