If you set hair particle length by a vertexgroup, it crashes randomly when painting weights.

Attachments:

hair_crash.blend
* Start painting those weights. For me it usually crashes within 10 seconds, sometimes takes longer.

corrupted_hair.png
* Just before it crashes, some hairs points get corrupted, and will be drawn as random lines to infinity.


Tested on SVN rev 34488, using both 32 and 64-bit Windows builds.


Crash backtrace:
Program received signal SIGSEGV, Segmentation fault.
0x008cbd29 in do_particle_interpolation (psys=0xf4c7b10, p=306, pa=0xf4d5400,
t=100.000015, frs_sec=24, pind=0x28fb20, result=0x28fb70)
at source/blender/blenkernel/intern/particle.c:1266
1266 while(pind->hkey[1]->time < real_t) {

#0 0x008cbd29 in do_particle_interpolation (psys=0xf4c7b10, p=306,
pa=0xf4d5400, t=100.000015, frs_sec=24, pind=0x28fb20, result=0x28fb70)
at source/blender/blenkernel/intern/particle.c:1266
#1 0x008d22da in psys_cache_paths (sim=0x28fcb0, cfra=1)
at source/blender/blenkernel/intern/particle.c:2956
#2 0x008efd25 in psys_update_path_cache (sim=0x28fcb0, cfra=1)
at source/blender/blenkernel/intern/particle_system.c:3189
#3 0x008f0450 in hair_step (sim=0x28fcb0, cfra=1)
at source/blender/blenkernel/intern/particle_system.c:3346
#4 0x008f2c31 in particle_system_update (scene=0xf4c5908, ob=0xf4c7688,
psys=0xf4c7b10) at source/blender/blenkernel/intern/particle_system.c:4129
#5 0x009b2d43 in deformVerts (md=0xa586b60, ob=0xf4c7688, derivedData=0x0,
vertexCos=0xa654a30, UNUSED_numVerts=289, UNUSED_useRenderParams=0,
UNUSED_isFinalCalc=1)
at source/blender/modifiers/intern/MOD_particlesystem.c:195
#6 0x008dd923 in mesh_calc_modifiers (scene=0xf4c5908, ob=0xf4c7688,
inputVertexCos=0x0, deform_r=0xf4c7a38, final_r=0xf4c7a3c,
useRenderParams=0, useDeform=1, needMapping=1, dataMask=1048601, index=-1,
useCache=1) at source/blender/blenkernel/intern/DerivedMesh.c:1720
#7 0x008decbf in mesh_build_data (scene=0xf4c5908, ob=0xf4c7688,
dataMask=1048601) at source/blender/blenkernel/intern/DerivedMesh.c:2245
#8 0x008dee47 in makeDerivedMesh (scene=0xf4c5908, ob=0xf4c7688, em=0x0,
dataMask=1048601) at source/blender/blenkernel/intern/DerivedMesh.c:2286
#9 0x0083838d in object_handle_update (scene=0xf4c5908, ob=0xf4c7688)
at source/blender/blenkernel/intern/object.c:2568
#10 0x00831e00 in scene_update_tagged_recursive (bmain=0xf494f08,
scene=0xf4c5908, scene_parent=0xf4c5908)
at source/blender/blenkernel/intern/scene.c:960
#11 0x00831e90 in scene_update_tagged (bmain=0xf494f08, scene=0xf4c5908)
at source/blender/blenkernel/intern/scene.c:980
#12 0x0040a1b4 in wm_event_do_notifiers (C=0x57b3b98)
at source/blender/windowmanager/intern/wm_event_system.c:305
#13 0x00403f5a in WM_main (C=0x57b3b98)
at source/blender/windowmanager/intern/wm.c:345
#14 0x00403796 in main (argc=1, argv=0x57b3480)
at source/creator/creator.c:1238