Crash when trying to write to the same text buffer from python after undo #53530
Labels
No Label
Interest
Alembic
Interest
Animation & Rigging
Interest
Asset Browser
Interest
Asset Browser Project Overview
Interest
Audio
Interest
Automated Testing
Interest
Blender Asset Bundle
Interest
BlendFile
Interest
Collada
Interest
Compatibility
Interest
Compositing
Interest
Core
Interest
Cycles
Interest
Dependency Graph
Interest
Development Management
Interest
EEVEE
Interest
EEVEE & Viewport
Interest
Freestyle
Interest
Geometry Nodes
Interest
Grease Pencil
Interest
ID Management
Interest
Images & Movies
Interest
Import Export
Interest
Line Art
Interest
Masking
Interest
Metal
Interest
Modeling
Interest
Modifiers
Interest
Motion Tracking
Interest
Nodes & Physics
Interest
OpenGL
Interest
Overlay
Interest
Overrides
Interest
Performance
Interest
Physics
Interest
Pipeline, Assets & IO
Interest
Platforms, Builds & Tests
Interest
Python API
Interest
Render & Cycles
Interest
Render Pipeline
Interest
Sculpt, Paint & Texture
Interest
Text Editor
Interest
Translations
Interest
Triaging
Interest
Undo
Interest
USD
Interest
User Interface
Interest
UV Editing
Interest
VFX & Video
Interest
Video Sequencer
Interest
Virtual Reality
Interest
Vulkan
Interest
Wayland
Interest
Workbench
Interest: X11
Legacy
Blender 2.8 Project
Legacy
Milestone 1: Basic, Local Asset Browser
Legacy
OpenGL Error
Meta
Good First Issue
Meta
Papercut
Meta
Retrospective
Meta
Security
Module
Animation & Rigging
Module
Core
Module
Development Management
Module
EEVEE & Viewport
Module
Grease Pencil
Module
Modeling
Module
Nodes & Physics
Module
Pipeline, Assets & IO
Module
Platforms, Builds & Tests
Module
Python API
Module
Render & Cycles
Module
Sculpt, Paint & Texture
Module
Triaging
Module
User Interface
Module
VFX & Video
Platform
FreeBSD
Platform
Linux
Platform
macOS
Platform
Windows
Priority
High
Priority
Low
Priority
Normal
Priority
Unbreak Now!
Status
Archived
Status
Confirmed
Status
Duplicate
Status
Needs Info from Developers
Status
Needs Information from User
Status
Needs Triage
Status
Resolved
Type
Bug
Type
Design
Type
Known Issue
Type
Patch
Type
Report
Type
To Do
No Milestone
No project
No Assignees
4 Participants
Notifications
Due Date
No due date set.
Dependencies
No dependencies set.
Reference: blender/blender#53530
Loading…
Reference in New Issue
No description provided.
Delete Branch "%!s(<nil>)"
Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?
System Information
Reproduces both on Ubuntu and Debian, different nvidia cards. Also reproduces on MacOS x64 and Win 10 x64.
Blender Version
Broken: both official 2.79 build and blender-2.79-e1eb1fbfca-linux-glibc219-x86_64 from builder.blender.org.
Short description of error
There is a scenario, when python script writes to the text buffer, then there is undo, and after that if script tries to write to the same buffer - blender crashes.
Initially this was found with Sverchok addon (see https://github.com/nortikin/sverchok/issues/1918 - an issue in sverchok repo, there also people saying they can reproduce this). Then I was able to reproduce the same with much simpler addon.
Exact steps for others to reproduce the error
Actual Result: on my Debian computer, blender crashes (will attach txt file). On Ubuntu computer, blender writes "Attempt to free NULL pointer" to console and hangs while eating 100% CPU.
Expected result: the same line of text appears again in the text buffer.
My humble guesses of what is going on: Python script stores a reference to Text object (it is initialized when you press "Init text buffer"). When user presses Ctrl-Z, that Text object is for some reason invalidated on C side. And when Python tries to write to the same object again, we have a crash.
Added subscriber: @portnov
blender.crash.txt - crash.txt from blender.
test.zip - sample script zipped.
Added subscribers: @mont29, @ideasman42, @VukGardasevic
The issue you are describing is noted in the Python documentation:
https://docs.blender.org/api/master/info_gotcha.html#undo-redo
Undo invalidates all the bpy.types.
The issue about text disappearing is listed as an To Do https://wiki.blender.org/index.php/Dev:Source/Development/Todo/UserInterface#Undo.2C_Redo_and_Operator_Context
Something like this seems to work:
You can notice that the object hash changes on Undo.
However, there could be some other issues related to valid calls using (getting the bpy,data.texts without storing it in a global in some corner cases).
@mont29, @ideasman42 should this be regarded as a bug? Thanks.
Thanks for the information.
Okay, if there are some (i beleive very good) reasons to invalidate bpy objecs on undo, let it be so. But, I do not think that crash is a good behaivour in such a case. IMHO blender should either throw python exception, or maybe just stop processing this script and print error to console, or show some pop-up error message, but not crash.
Added subscriber: @tetha.z
Changed status from 'Open' to: 'Resolved'