Re: beginner needs help with "casting" with gtk

[Mike Massonnet <mmassonnet gmail com>]

Le dimanche 21 juin 2009 14:20:17, David Nečas a écrit :
> On Sun, Jun 21, 2009 at 02:13:52PM +0200, Julien Martin wrote:
> > *static void hello(GtkWidget *widget, gpointer data) {
> >     gchar * _data = (gchar *) data;

There is no need to cast a gpointer.

> >     g_print(_data);

Same as David, never put a variable for the format of printf like functions, 
always use %s e.g. fooprintf("%s", variable).

Mike

> >     g_print("\n");
> > }*
> >
> > wich I call as follows:
> > *
> > g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(hello), "hello
> > toto");*
> >
> > I get the following warning each time I compile:
> >
> > *warning: the format is not a litteral string and no format argument*
> >
> > Can anyone please help?
> > I need to "cast" the data variable to gchar *. What am I doing wrong?
>
> The problem is not in the typecasting.  The problem is that if you do
> (directly or indirectly)
>
>   g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(hello), "%s");
>
> your program will crash.  Print the message as
>
>   g_print("%s\n", data);
>
> Yeti
>
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