Re: [gtk-list] More tutorial

[Martin Norb{ck <d95mback dtek chalmers se>]

On Tue, 29 Jul 1997, Ian Main wrote:

>      /* this is a callback function. the data arg is ignored..
>       * More on callbacks below. */
>      void hello (gpointer *data)
>      {
>         g_print ("Hello World\n");
>      }
[SNIP]
>         * defined above. */
>        gtk_signal_connect (GTK_OBJECT (button), "clicked",
>                            GTK_SIGNAL_FUNC (hello), NULL);
One little comment.
The clicked signal has declaration:
void GtkButton::Clicked( GtkButton* button );
which means that the callback really should have type
void hello( GtkButton* button, gpointer* data );
where the button argument is the button that sent the signal.

Since you are not using the data in this example there is nothing to worry
about, but if you try to use it you will probably get an error.

Since the C calling convention allows any number of arguments to any function,
the above code will work. The type checker can't check this either, because
the hello function is casted anyway, so it's a bit of a problem really.

----- BEGIN FLAME PROTECTION -----
I hope I am right; I gathered this information by reading the source code. If I
am wrong could someone please tell me, because that may fix some of the bugs
in my programs!
----- END FLAME PROTECTION -----

/norpan

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