Most Telepathy(-related) C components define DEBUG(...) to do { } while (0); if --disable-debug is passed to configure. This has the unpleasant side-effect of triggering unused variable warnings and the like.

I realised today that they could instead be defined as follows:

  static inline void
  DEBUG (const gchar *format, ...)
  {
  }

This avoids us ever having to guard variables only used in debug statements with ENABLE_DEBUG ever again. If the compiler is smart enough (which it should be), it will optimise away the function call; if it's *really* smart it'll also optimize away the variables which (after the function call has been eliminated) are set but never used. (I don't know how smart GCC is, but it *should* do at least the first.)

I've got branches for Wocky and tp-glib so far. I vetted tp-glib and there are no particularly expensive function calls as arguments to DEBUG(). The most expensive is tp_handle_set_size().

http://cgit.collabora.com/git/user/wjt/wocky.git/log/?h=oh-god-the-warnings
http://cgit.collabora.com/git/user/wjt/telepathy-glib.git/log/?h=debug-stub