[Wayland-bugs] [Bug 787069] gdk_keymap_get_entries_for_keyval() returns TRUE with n_keys=0 in Wayland

[gtk+ (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=787069

--- Comment #3 from Carlos Garcia Campos <carlosgc at gnome.org> ---
(In reply to Christian Persch from comment #2)
> Existing code using this may do
> 
> if (gdk_keymap_get_entries_for_keyval(..., &keys, &n_keys)) {
>   /* do something */
>   g_free(keys);
> }
> 
> (e.g. firefox does this).
> 
> The patch returns FALSE on n_keys == 0, but still keys != NULL, which means
> a leak on the code pattern above. Should also change to set return keys =
> NULL in this case, I think.

I'm not sure that can happen, at least in the mir and wayland implementations,
if n_keys == 0, then they GArray was created but never changed, so the internal
pointer is still NULL. The GArray itself is freed, so I don't think there's any
leak. We could still do the same X11 backend does to be extra sure:

  if (retval->len > 0)
    {
      *keys = (GdkKeymapKey*) retval->data;
      *n_keys = retval->len;
    }
  else
    {
      *keys = NULL;
      *n_keys = 0;
    }

  g_array_free (retval, retval->len > 0 ? FALSE : TRUE);

  return *n_keys > 0;

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