# Slicer exit error

**URL:** <https://discourse.slicer.org/t/slicer-exit-error/12921>\
**Category:** Development\
**Tags:** bug\
**Created:** [August 10, 2020, 5:47am UTC](https://discourse.slicer.org/t/slicer-exit-error/12921 "2020-08-10T05:47:41Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Tesla2687](https://avatars.discourse-cdn.com/v4/letter/t/c4cdca/32.png) [@Tesla2687](https://discourse.slicer.org/u/Tesla2687)\
**Post date:** [August 10, 2020, 5:47am UTC](https://discourse.slicer.org/t/slicer-exit-error/12921/1 "2020-08-10T05:47:41Z")

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Operating system: Windows 10  
Slicer version: Slicer 4.11.0  
Expected behavior:  
Actual behavior:

When I exit the Slicer, something wrong happened. please check the screenshot below.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/8/a/8ad7bc8e1f278e2719cada672bc48ae87dfa1a03.jpeg)

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**Author:** ![pieper](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/pieper/32/8_2.png) [@pieper](https://discourse.slicer.org/u/pieper)\
**Post date:** [August 10, 2020, 12:23pm UTC](https://discourse.slicer.org/t/slicer-exit-error/12921/2 "2020-08-10T12:23:11Z")

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Hi, thanks for the report. Please add what steps led to this (what extensions were installed, what operations you performed). Generally memory leaks like this aren’t harmful but we’d like to clean them up.

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [August 10, 2020, 1:32pm UTC](https://discourse.slicer.org/t/slicer-exit-error/12921/3 "2020-08-10T13:32:05Z")

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The first listed object that you haven’t released from memory is a `vtkCollection`, which usually indicates that you have forgot to call `UnRegister` for a collection returned by a factory method, such as `slicer.mrmlScene.GetNodesByClass`.

See these pages for more information:

- [Developer FAQ- memory management](https://www.slicer.org/wiki/Documentation/Nightly/Developers/Tutorials/MemoryManagement)
- [Tracking memory leaks](https://www.slicer.org/wiki/Documentation/Nightly/Developers/Tutorials/Troubleshooting#Track_memory_leaks)

`Deleting unknown object` error might indicate that something wrong with how the VTK object is constructed. Make sure you follow example of other MRML nodes exactly (e.g., you use `vtkStandardNewMacro` to implement `New()` method).

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**Author:** ![Tesla2687](https://avatars.discourse-cdn.com/v4/letter/t/c4cdca/32.png) [@Tesla2687](https://discourse.slicer.org/u/Tesla2687)\
**Post date:** [August 14, 2020, 7:37am UTC](https://discourse.slicer.org/t/slicer-exit-error/12921/4 "2020-08-14T07:37:43Z")

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Hello Steve,

The problem has been solved after delete one extenson.

Thank you very much.

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**Author:** ![Tesla2687](https://avatars.discourse-cdn.com/v4/letter/t/c4cdca/32.png) [@Tesla2687](https://discourse.slicer.org/u/Tesla2687)\
**Post date:** [August 14, 2020, 7:37am UTC](https://discourse.slicer.org/t/slicer-exit-error/12921/5 "2020-08-14T07:37:57Z")

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Hello Andras,

The problem has been solved after delete one extenson.

Thank you very much.