(gdb) bt
#0  0x00000000004696b2 in __wt_cell_type (cell=0x0)
    at ../src/include/cell.i:470
WT-1  0x0000000000469850 in __wt_cell_unpack_safe (page=0x0, cell=0x0, 
    unpack=0x7fe5ebcb76b0, end=0x0) at ../src/include/cell.i:572
WT-2  0x0000000000469c79 in __wt_cell_unpack (cell=0x0, unpack=0x7fe5ebcb76b0)
    at ../src/include/cell.i:714
WT-3  0x000000000046eb88 in __rec_col_merge (session=0xd65510, r=0x7fe59c04d7b0, 
    page=0x7fe5a4038e40) at ../src/btree/rec_write.c:2381
WT-4  0x000000000046eb24 in __rec_col_merge (session=0xd65510, r=0x7fe59c04d7b0, 
    page=0x7fe54803dfe0) at ../src/btree/rec_write.c:2364
WT-5  0x000000000046e909 in __rec_col_int (session=0xd65510, r=0x7fe59c04d7b0, 
    page=0x7fe54803dfe0) at ../src/btree/rec_write.c:2307
WT-6  0x000000000046af9d in __wt_rec_write (session=0xd65510, 
    page=0x7fe54803dfe0, salvage=0x0, flags=0) at ../src/btree/rec_write.c:356
WT-7  0x000000000044ff0d in __wt_sync_file (session=0xd65510, syncop=8)
    at ../src/btree/bt_evict.c:649
WT-8  0x000000000045fb68 in __wt_bt_cache_op (session=0xd65510, 
    ckptbase=0x7fe59c061550, op=8) at ../src/btree/bt_sync.c:53
WT-9  0x0000000000449ad7 in __checkpoint_worker (session=0xd65510, 
    cfg=0x7fe5ebcb7cf0, is_checkpoint=1) at ../src/txn/txn_ckpt.c:750
WT-10 0x0000000000449ce1 in __wt_checkpoint (session=0xd65510, 
    cfg=0x7fe5ebcb7cf0) at ../src/txn/txn_ckpt.c:802
WT-11 0x0000000000497c6e in __wt_meta_btree_apply (session=0xd65510, 
    func=0x449c79 <__wt_checkpoint>, cfg=0x7fe5ebcb7cf0)
    at ../src/meta/meta_apply.c:45
WT-12 0x0000000000448838 in __checkpoint_apply (session=0xd65510, 
    cfg=0x7fe5ebcb7cf0, op=0x449c79 <__wt_checkpoint>, fullp=0x0)
    at ../src/txn/txn_ckpt.c:129
WT-13 0x0000000000448b1e in __wt_txn_checkpoint (session=0xd65510, 
    cfg=0x7fe5ebcb7cf0) at ../src/txn/txn_ckpt.c:243
WT-14 0x000000000043fe2d in __session_checkpoint (wt_session=0xd65510, 
    config=0x7fe5ebcb7d80 "name=thread-10") at ../src/session/session_api.c:716
WT-15 0x000000000040fb9c in ops (arg=0xd83250) at ../../../test/format/ops.c:272
WT-16 0x0000003789207851 in start_thread () from /lib64/libpthread.so.0
WT-17 0x0000003788ae767d in clone () from /lib64/libc.so.6

(gdb) frame 3
WT-3  0x000000000046eb88 in __rec_col_merge (session=0xd65510, r=0x7fe59c04d7b0, 
    page=0x7fe5a4038e40) at ../src/btree/rec_write.c:2381
2381				__wt_cell_unpack(ref->addr, unpack);
(gdb) p *ref
$2 = {page = 0x0, addr = 0x0, key = {recno = 0, ikey = 0x0, pkey = 0}, 
  txnid = 0, state = WT_REF_DISK, unused = 0}
(gdb) p *page
$3 = {parent = 0x7fe5a40229e0, ref = 0x7fe5a4000078, u = {intl = {recno = 0, 
      t = 0x0}, row = {d = 0x0, ins = 0x0, upd = 0xabababababababab}, 
    col_fix = {recno = 0, bitf = 0x0}, col_var = {recno = 0, d = 0x0, 
      repeats = 0xabababababababab, nrepeats = 2880154539}}, 
  dsk = 0xabababababababab, modify = 0xabababababababab, 
  read_gen = 12370169555311111083, memory_footprint = 12370169555311111083, 
  entries = 2880154539, type = 171 '\253', flags_atomic = 171 '\253'}