#0  0x0000003fe7035c39 in raise () from /lib64/libc.so.6
#1  0x0000003fe7037348 in abort () from /lib64/libc.so.6
#2  0x00000000023de545 in dm_ensure_display_normals (dm=0x7fffcc001838)
    at /home/terry/BLENDER-GIT/EXTERNALSOURCES/BLENDER/source/blender/blenkernel/intern/DerivedMesh.c:1427
#3  0x00000000023df66d in mesh_calc_modifiers (scene=0x8069b88, ob=0x8071c98, 
    inputVertexCos=0x0, deform_r=0x80721a0, final_r=0x80721a8, 
    useRenderParams=0, useDeform=1, needMapping=0, dataMask=637534233, 
    index=-1, useCache=1, build_shapekey_layers=0)
    at /home/terry/BLENDER-GIT/EXTERNALSOURCES/BLENDER/source/blender/blenkernel/intern/DerivedMesh.c:1888
#4  0x00000000023e0d43 in mesh_build_data (scene=0x8069b88, ob=0x8071c98, 
    dataMask=637534233, build_shapekey_layers=0)
    at /home/terry/BLENDER-GIT/EXTERNALSOURCES/BLENDER/source/blender/blenkernel/intern/DerivedMesh.c:2241
#5  0x00000000023e1072 in makeDerivedMesh (scene=0x8069b88, ob=0x8071c98, 
    em=0x0, dataMask=637534233, build_shapekey_layers=0)
    at /home/terry/BLENDER-GIT/EXTERNALSOURCES/BLENDER/source/blender/blenkernel/intern/DerivedMesh.c:2314
#6  0x00000000025282bd in BKE_object_handle_update_ex (eval_ctx=0x7f4b158, 
    scene=0x8069b88, ob=0x8071c98, rbw=0x0, do_proxy_update=false)
    at /home/terry/BLENDER-GIT/EXTERNALSOURCES/BLENDER/source/blender/blenkernel/intern/object.c:2916
---Type <return> to continue, or q <return> to quit---
#7  0x000000000258450f in scene_update_object_func (pool=0x7f7f238, 
    taskdata=0x7f55958, threadid=1)
    at /home/terry/BLENDER-GIT/EXTERNALSOURCES/BLENDER/source/blender/blenkernel/intern/scene.c:1347
#8  0x0000000002712260 in task_scheduler_thread_run (thread_p=0x7e430d8)
    at /home/terry/BLENDER-GIT/EXTERNALSOURCES/BLENDER/source/blender/blenlib/intern/task.c:137
#9  0x0000003fe7407f33 in start_thread () from /lib64/libpthread.so.0
#10 0x0000003fe70f4ded in clone () from /lib64/libc.so.6
(gdb)