[Gtk2hs-commit] (main branch): Reimplement the way we keep track of gthread initialisation state

[Duncan C. <dun...@wo...>]

Tue Jul  3 18:24:35 PDT 2007  Duncan Coutts <du...@ha...>
  * Reimplement the way we keep track of gthread initialisation state
  Sadly we cannot just call g_thread_supported() because this macro expands
  into a reference to a gloabl variable that lives in the gthread dynamic lib.
  On windows, GHCi's dynamic linker cannot cope with references to global vars
  from C dlls. So instead we keep a global var in the wrapper, so it's in the
  same package, rather than crossing a dll boundary. This allows us to track
  the state, and because the state is allocated in C land, it survives :reload
  in GHCi, which was the problem with the original scheme. Ugg.

    hunk ./gtk/Graphics/UI/Gtk/General/General.chs 163
    -initialiseGThreads :: IO ()
    -initialiseGThreads = do
    -  gthreadsInitialised <- liftM (toBool . fromIntegral) gtk2hs_thread_supported
    -  when (not gthreadsInitialised) $ do
    -    {# call unsafe g_thread_init #} nullPtr
    -
    -foreign import ccall "hsgthread.h gtk2hs_thread_supported"
    -  gtk2hs_thread_supported :: IO CInt
    +foreign import ccall "hsgthread.h gtk2hs_threads_initialise"
    +  initialiseGThreads :: IO ()
    hunk ./gtk/Graphics/UI/Gtk/General/hsgthread.c 1
    -/* Annoyingly, g_thread_supported is actuall a macro so we need this silly
    - * little wrapper functions. Grrr. */
    +/* We would use the g_thread_supported macro here, but unfortunately on
    + * windows GHCi's dynamic linker cannot cope with references to global
    + * variables imported from dlls.
    + *
    + * So instead of asking glib if we (or indeed) anyone else has initialised
    + * the glib gthread system, we keep track of it ourselves. We still have to
    + * do it in C land so the state survives :reload in GHCi. So there is the
    + * danger in a mixed language program, of someone else initialising the
    + * glib thread system and us not being aware of it. :-(
    + */
    hunk ./gtk/Graphics/UI/Gtk/General/hsgthread.c 14
    -int gtk2hs_thread_supported () {
    -  return g_thread_supported();
    +void gtk2hs_threads_initialise () {
    +  static int threads_initialised = 0;
    +
    +  if (!threads_initialised) {
    +    threads_initialised = 1;
    +    g_thread_init(NULL);
    +  }
    hunk ./gtk/Graphics/UI/Gtk/General/hsgthread.h 1
    -/* g_thread_supported wrapper function */
    -
    -int gtk2hs_thread_supported ();
    +int gtk2hs_threads_initialise ();