Crash when joining objects in a loop #73700

New Issue

Robert Guetzkow · 2020-02-09T23:56:40+01:00

Robert Guetzkow commented

2020-02-09 23:56:40 +01:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.30

Blender Version
Broken: version: 2.83 (sub 2), branch: master, commit date: 2020-02-09 16:59, hash: 5314161491

Short description of error

This problem was originally discovered by Eduardo Ramírez .

Joining objects while iterating over a collection of objects, e.g. bpy.context.view_layer.objects or bpy.context.scene.objects, results in a crash.

It's possible that this isn't supposed to work, since the collection that is being iterated over is modified inside the loop, which is rarely a good thing. This issue is similar to #60491 which was closed because it couldn't be reproduced.

Exact steps for others to reproduce the error

Open the attached blend file
Run the script

crash_mwe.blend

import bpy


for obj in bpy.context.view_layer.objects:
    bpy.ops.object.select_all(action='SELECT')
    bpy.context.view_layer.objects.active = obj
    bpy.ops.object.join()

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.30 **Blender Version** Broken: version: 2.83 (sub 2), branch: master, commit date: 2020-02-09 16:59, hash: `5314161491` **Short description of error** This problem was originally discovered by [Eduardo Ramírez ](https://blender.stackexchange.com/questions/166410/script-randomly-crashes-blender). Joining objects while iterating over a collection of objects, e.g. `bpy.context.view_layer.objects` or `bpy.context.scene.objects`, results in a crash. It's possible that this isn't supposed to work, since the collection that is being iterated over is modified inside the loop, which is rarely a good thing. This issue is similar to #60491 which was closed because it couldn't be reproduced. **Exact steps for others to reproduce the error** - Open the attached blend file - Run the script [crash_mwe.blend](https://archive.blender.org/developer/F8331656/crash_mwe.blend) ``` import bpy for obj in bpy.context.view_layer.objects: bpy.ops.object.select_all(action='SELECT') bpy.context.view_layer.objects.active = obj bpy.ops.object.join() ```

Robert Guetzkow commented

2020-02-09 23:56:40 +01:00

Added subscriber: @rjg

Robert Guetzkow commented

2020-02-09 23:59:50 +01:00

The crash occurs in the loop when the next element is accessed.

pyrna_struct_CreatePyObject(PointerRNA * ptr) Line 7264	C
pyrna_prop_collection_iter_next(BPy_PropertyCollectionIterRNA * self) Line 6955	C
[External Code]

The crash occurs in the loop when the next element is accessed. ``` pyrna_struct_CreatePyObject(PointerRNA * ptr) Line 7264 C pyrna_prop_collection_iter_next(BPy_PropertyCollectionIterRNA * self) Line 6955 C [External Code] ```

Robert Guetzkow changed title from ~~Crash when joining in a loop~~ to Crash when joining objects in a loop

2020-02-10 00:49:38 +01:00

Robert Guetzkow commented

2020-02-10 09:49:20 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Campbell Barton commented

2020-02-11 06:15:50 +01:00

Added subscriber: @ideasman42

Campbell Barton commented

2020-02-11 06:15:50 +01:00

Changed status from 'Confirmed' to: 'Archived'

Campbell Barton closed this issue

2020-02-11 06:15:50 +01:00

Campbell Barton self-assigned this 2020-02-11 06:15:50 +01:00

Campbell Barton commented

2020-02-11 06:15:50 +01:00

This is a known limitation in the Python API.

See https://docs.blender.org/api/master/info_gotcha.html#removing-data

This is a known limitation in the Python API. See https://docs.blender.org/api/master/info_gotcha.html#removing-data

Robert Guetzkow commented

2020-02-11 10:15:40 +01:00

@ideasman42 Thank you for confirming that this is a known limitation. I wasn't sure if the gotcha applies to implicit removal through operators and if there were any safe-guards implemented for that case. Modifying an iterable while iterating over it is not a good idea anyway.

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Crash when joining objects in a loop #73700