Question

I have a function (see below) that is emitting the following warning:

second parameter of ‘va_start’ not last named argument

What does it means and how to remove it?

The function is as the following:

static int  ui_show_warning(GtkWindow *parent, const gchar *fmt, size_t size, ...)
    {
      GtkWidget *dialog = NULL;
      va_list args = NULL;
      int count = -1;
      char *msg = NULL;

      if((msg = malloc(size + 1)) == NULL)
        return -12;

      va_start(args, fmt);

      if((count = snprintf(msg, size, fmt, args)) < 0)
        goto outer;

      dialog = gtk_message_dialog_new(parent,
                      GTK_DIALOG_DESTROY_WITH_PARENT,
                      GTK_MESSAGE_WARNING,
                      GTK_BUTTONS_OK,
                      "%s", msg);
      (void) gtk_dialog_run(GTK_DIALOG(dialog));

      gtk_widget_destroy(dialog);

     outer: {
        if(args != NULL)
          va_end(args);

        if(msg != NULL)
          free(msg);

        return count;
      }
    }

Answer 1

You need to use size instead of fmt:

va_start(args, size);

It is size, not fmt, that is the last parameter that has an explicit name (as opposed to vararg parameters, which have no names). You need to pass the last named parameter to va_start in order for it to figure out the address in memory at which the vararg parameters start.