threadobj_unblock() simply does not work, dereferencing a NULL pointer
whenever it actually manages to unblock a thread waiting on a
synchronization object.

Calling syncobj_flush() on this object to wake up waiters zeroes the
wait_sobj field in the corresponding TCBs, so don't dereference
thobj->wait_sobj past this point.

Thread 1 "main" received signal SIGSEGV, Segmentation fault.
0x00007ffff79aeda0 in __syncobj_tag_unlocked (sobj=0x0) at include/copperplate/syncobj.h:100
100		assert(sobj->flags & SYNCOBJ_LOCKED);
(gdb) bt