finalize, dispose and destroy

[Paul Pogonyshev <pogonyshev gmx net>]

Can anyone explain (point to explanation) the difference between these
three methods?  I.e., when implementing a new widget, where do I put
freeing of which resources?  It seems that a single widget can catch
`destroy' signal more than once.  Is this true for finalize/dispose?

Also is there a nice way to watch for memory leaks under GTK+?
Valgrind seems to report many leaks that originate not in my program,
but in X or GTK+.

Thanks in advance
  Paul