I need to make a macro to typecast (right word?) pointer struct from a function parameter. This is my struct:

typedef struct _AppData {
    GtkWidget* toplevel; // main window
    GtkWidget* view; // column style view
    GtkWidget* entry_outdir; // output dir
    GtkWidget* entry_artist; // artist
    GtkWidget* entry_title; // title
    GtkWidget* entry_link; // link
    GtkWidget* check_jman; // bool for jman
    GtkWidget* menuitem_clear; // init states
    GtkWidget* menuitem_action; // play/stop menu item
} AppData, *PAppData;

somewhere in my code is used like this:

g_signal_connect (G_OBJECT (button), "clicked", G_CALLBACK (cb_select_folder), pad);
void cb_select_folder (GtkButton* sender, gpointer user_data)
{
  PAppData pad = PAPPDATA(user_data); # typecast macro here
  const gchar* dirname = gtk_entry_get_text (GTK_ENTRY(pad->entry_outdir));
  // ..
}

To create the macro I’m trying this:

#define PAPPDATA(_in_) (PAppData(_in_))

and I get error: expected ‘)’ before ‘user_data’
Any help?