Created attachment 20385 [details]
[PATCH] Drop bogus size check

Commit eed3bad23510e59278bdaa5f7d0ab01fc1a1c21b [1] introduces a display_callback v3, leaving the support for the former display_callback now known as v2.
The problem is that the struct sizes check added for v2 compatibility is broken:
in the "display_check_structure" function of devices/gdevdsp.c there is:

static int display_check_structure(gx_device_display *ddev)
[...]
    else if (ddev->callback->size == sizeof(struct display_callback_v2_s)) {
        /* V2 structure with added display_separation callback */
        if (ddev->callback->size != sizeof(display_callback))
            return_error(gs_error_rangecheck);
[...]

Considering that:
- sizeof(struct display_callback_v2_s) != sizeof(display_callback);
  the addition to new stuff to display_callback was the reason for the
  new struct in the first place, so of course the two structs do not
  have the same size
- the last libspectre build uses display_callback v2, so the check:
  ddev->callback->size == sizeof(struct display_callback_v2_s)
  is true
then the check "ddev->callback->size != sizeof(display_callback)" will be always false, and thus always returning errors when running an application/library that was built with display_callback v2.

It looks to me it was a simple copy&paste mistake, and indeed the aforementioned check makes display_callback v2 working again; attached the easy patch for this.

[1] http://git.ghostscript.com/?p=ghostpdl.git;a=commit;h=eed3bad23510e59278bdaa5f7d0ab01fc1a1c21b