This is a general toolkit-wide problem that I am unsure how to go
about reporting right.

Consider, as an example, the function gdk_window_set_event_compression.
Its semantics looks obvious from the code, but it is not.  s_e_c(w,FALSE)
turns compression off; s_e_c(w,TRUE) turns it on.  Easy.  But:

   s_e_c(w,2) turns it OFF.

The assignment will overflow the single-bit structure member and assign 0.
This kind of thing obviously doesn't happen with a constant 2, but it can
reasonably happen with, say, flag tests.

Solution here: !!

But how does one find all the cases of this?




void
gdk_window_set_event_compression (GdkWindow *window,
                                  gboolean   event_compression)
{
  g_return_if_fail (GDK_IS_WINDOW (window));

  window->event_compression = event_compression;
}