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Blender crash when creating node tree links with Python
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Description

System Information
Operating system: Windows 10 Home
Graphics card: Intel HD Graphics 505, Intel HD Graphics 2500

Blender Version
Broken: 2.78c, 2.79, 2.79b
Worked: Untested on other Blender versions

Short description of error
When a Python script creates a node tree in bpy.data.node_groups, creates nodes in that tree using node_tree.nodes.new(), and attempts to create a link between nodes using node_tree.links.new(), there is a 5-10% chance that the link creation step fails. During such a failure, Blender crashes, and the console prints Error: EXCEPTION_ACCESS_VIOLATION. This can happen when the script is run from Blender's text editor or from an add-on. This is confirmed to occur in Blender 2.78c, 2.79, and 2.79b on two separate Windows 10 Home computers. It does not occur when running Blender in Ubuntu 17.10 using VirtualBox on those same computers.

Exact steps for others to reproduce the error
Open the attached file Node_Tree_Link_Bug.blend and repeatedly run the Python script named Text. A crash may occur the first time the script is run, or a crash may occur after the script is run several times. It is occasionally necessary to run the script dozens of times before a crash occurs.

Note that the attached file produces two links. When a crash occurs, it almost always (>95% of the time) occurs when the first link is being made, and if the first link is successfully made, then the second one is virtually always made as well. I've only seen the second link cause a crash once out of hundreds of script executions.

Details

Type
Bug

Event Timeline

This comment was removed by Cody (bldebg).

Seems I cant reproduce.
Made several runs in both master and 2.79 (each running the script 100 times)

Does this happen on other computers as well?
Does this happen with Factory settings as well?

@Philipp Oeser (lichtwerk)

“Does this happen on other computers as well?”

Yes, I confirmed the same exact crashes in 2.78c on a different PC running Windows 10 Home. However, when I run the Blender scripts in Ubuntu 17.10 using VirtualBox on those same computers, the crashes do not happen. I've updated the task description with these details as well.

“Does this happen with Factory settings as well?”

Yes. I uninstalled Blender, deleted Blender's temporary and hidden configuration files, reinstalled 2.79b, and the crashes still happen in the default Blender installation.

Please let me know if there is additional information I can provide to help solve this issue.

OK, seems like a Windows issue then (I'm on linux as well).
Someone here on Windows can reproduce?

I tried this on win 7 gtx 550ti master hash d5c1c0b, every things seems okay, I run the script till my Mem was 50.90M i don't remember how many times but more than needed :)

Video of the error: https://www.dropbox.com/s/zvw4c1v78n55wef/Blender_Tree_Link_Bug.mp4?dl=0

I can provide any additional information that anything thinks is useful in solving this bug.