The type key_callback has got a real prototype.

src/main.c

@@ -1238,7 +1238,7 @@ static const key_map ctl_x_map[] = {
 static int ctl_x_map_enabled = 0;
 
 static void
-ctl_x_cmd (int ignore)
+ctl_x_cmd (void)
 {
     ctl_x_map_enabled = 1;
 }
@@ -1468,7 +1468,7 @@ midnight_callback (struct Dlg_head *h, dlg_msg_t msg, int parm)
 	    ctl_x_map_enabled = 0;
 	    for (i = 0; ctl_x_map[i].key_code; i++)
 		if (parm == ctl_x_map[i].key_code) {
-		    (*ctl_x_map[i].fn) (parm);
+		    (*ctl_x_map[i].fn) ();
 		    return MSG_HANDLED;
 		}
 	}
@@ -1564,13 +1564,13 @@ midnight_callback (struct Dlg_head *h, dlg_msg_t msg, int parm)
 	    ctl_x_map_enabled = 0;
 	    for (i = 0; ctl_x_map[i].key_code; i++)
 		if (parm == ctl_x_map[i].key_code) {
-		    (*ctl_x_map[i].fn) (parm);
+		    (*ctl_x_map[i].fn) ();
 		    return MSG_HANDLED;
 		}
 	} else {
 	    for (i = 0; default_map[i].key_code; i++) {
 		if (parm == default_map[i].key_code) {
-		    (*default_map[i].fn) (parm);
+		    (*default_map[i].fn) ();
 		    return MSG_HANDLED;
 		}
 	    }

src/main.h

@@ -73,10 +73,7 @@ extern int is_right;		/* If the selected menu was the right */
 #define MENU_PANEL_IDX  (is_right ? 1 : 0)
 #define SELECTED_IS_PANEL (get_display_type (is_right ? 1 : 0) == view_listing)
 
-typedef void (*key_callback) ();
-/* FIXME: We have to leave this type ambiguous, because `key_callback'
-   is used both for functions that take an argument and ones that don't.
-   That ought to be cleared up. */
+typedef void (*key_callback) (void);
 
 /* The keymaps are of this type */
 typedef struct {