I hit an infinite loop on gselect.c:58-59. After quick debugging I found
that the problem is in loop xgselect.c:58-59:

while(n_gfds > gfds_size)
  gfds_size *= 2;

Problem is that:

(gdb) p n_gfds
$3 = 1
(gdb) p gfds_size
$4 = 0

1. It seems that xgselect_initialize was not called as X system is
initialized.

2. Is there a reason why the code is not using (much more efficient but
equivalent) such code in the first place:

if (ngfds > gfds_size)
  {
    gfds_size = 1 << g_bit_storage (ngfds);
    xfree (gfds);
    gfds = xmalloc (sizeof (*gfds) * gfds_size);
  }

3. The attached file get rids of initialization at all initializing at
the cost of conditional freeing of gfds (and starting mallocing from 1
instead of 128).

Best regards