I've installed glib2-devel-2.34.2-1.fc18.x86_64 and the code evolution-data-server generates with help of gdbus-codegen produces compiler warnings like this one:

   e-dbus-source.c:329:1: warning: redundant redeclaration of
   'e_dbus_source_default_init' [-Wredundant-decls]
   e-dbus-source.c:282:1: note: previous definition of
   'e_dbus_source_default_init' was here

The only issue with the generated code is that the
   typedef EDBusSourceIface EDBusSourceInterface;
   G_DEFINE_INTERFACE (EDBusSource, e_dbus_source, G_TYPE_OBJECT);

should be added *before*
   static void
   e_dbus_source_default_init (EDBusSourceIface *iface)
   {
    ...
   }

while it's currently after.

The warnings are easy to fix on the gdbus-codegen side, and are rather disturbing when one tries to keep code compiler-warning-free (not that eds is currently, but that's another thing). The eds currently rebuilds the code whenever compiled (no idea why it does that), thus the only possible fix is in the gdbus-codegen itself.