100% repro errors and crash using BMesh.free() in conjunction with bmesh.from_edit_mesh() and bmesh.update_edit_mesh() #39121

System Information
Linux Mint 16, nvidia GTX 460 (not sure if relevant

Blender Version
Broken: 2.70-RC1 and 2.69
Worked: ?

Python snippet:


import bmesh, bpy
mesh = bpy.context.active_object.data
bm = bmesh.from_edit_mesh(mesh)

for edge in bm.edges:
    edge.select = False

bmesh.update_edit_mesh(mesh)
bm.free()

REPRO STEPS:

Run script, it works
Run script again, check console
Run script again, check console
Tab out of edit mode, then back in
Run script again, crashes Blender
If bm.free() is removed, no errors

Changed status to: 'Open'

Added subscriber: @vravCodyBurrow

Attaching 27RC_bmesh_crash.blend with snippet loaded and ready to load.

Error output data included, here for convenience...

After first fail:

Traceback (most recent call last):
  File "/home/vrav/Documents/27RC_bmesh_crash.blend/Text", line 6, in <module>
ReferenceError: BMesh data of type BMesh has been removed
Error: Python script fail, look in the console for now...

After second fail:

Traceback (most recent call last):
  File "/home/vrav/Documents/27RC_bmesh_crash.blend/Text", line 6, in <module>
AttributeError: 'bytes' object has no attribute 'edges'
Error: Python script fail, look in the console for now...

Segmentation fault crash dump:

 Blender 2.70 (sub 0), Commit date: 2014-03-05 18:37, Hash 19f7f9a
bpy.ops.object.editmode_toggle()  # Operator
bpy.ops.text.run_script()  # Operator
bpy.ops.text.run_script()  # Operator
Python script fail, look in the console for now...  # Error
bpy.ops.text.run_script()  # Operator
Python script fail, look in the console for now...  # Error
bpy.ops.object.editmode_toggle()  # Operator
bpy.ops.object.editmode_toggle()  # Operator

 backtrace
./blender() [0xfbe704]
./blender() [0xfbe95a]
/lib/x86_64-linux-gnu/libc.so.6(+0x36ff0) [0x7f971bc53ff0]
./blender(PyObject_Malloc+0x5c) [0x2bec96c]
./blender(_PyObject_New+0xd) [0x2be9bbd]
./blender(BPy_BMEdge_CreatePyObject+0x74) [0x1864db4]
./blender(PyEval_EvalFrameEx+0x327f) [0x2c501ff]
./blender(PyEval_EvalCodeEx+0x83b) [0x2c4ceab]
./blender(PyEval_EvalCode+0x3b) [0x2c4cf7b]
./blender() [0x18571aa]
./blender() [0x120757c]
./blender() [0xfda062]
./blender() [0xfda560]
./blender() [0x129cb3a]
./blender() [0x12ac22b]
./blender() [0xfdb8c5]
./blender() [0xfdbbd6]
./blender(wm_event_do_handlers+0x19a) [0xfdbeca]
./blender(WM_main+0x18) [0xfc5fb8]
./blender(main+0x501) [0xfc0f8a]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5) [0x7f971bc3ede5]
./blender() [0xedace5]

Added subscriber: @florianfelix

Same thing:

import bmesh, bpy
mesh=bpy.context.object.data

bm = bmesh.from_edit_mesh(mesh)

#sort verts after z coordinate

sort = sorted(bm.verts, key=lambda v: v.co.z)

#select lowest

sort[0].select = True

bmesh.update_edit_mesh(mesh)

bm.free()


'''
This codes works the first time it is run.
Produces an error on subsequent runs.
Then crashes on autocomplete in the console.
'''

Changed status from 'Open' to: 'Archived'

bmesh.from_edit_mesh() does not create a bmesh, it returns the one associated with given mesh (that’s why mesh has to be in EditMode, else it has no bmesh associated with it). So the bmesh you get must never be freed!!! This is internal Blender data, created when entering EditMode and freed when leaving it.

Not a bug, closing.

thanks for clarification.
Sorry for false positive

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100% repro errors and crash using BMesh.free() in conjunction with bmesh.from_edit_mesh() and bmesh.update_edit_mesh() #39121

Same thing: