Seg fault crash with various edit functions #90532

System Information
Operating system: Linux-5.10.55-1-MANJARO-x86_64-with-glibc2.33 64 Bits
Graphics card: Mesa DRI Intel(R) HD Graphics 4600 (HSW GT2) Intel Open Source Technology Center 4.5 (Core Profile) Mesa 21.1.6

Blender Version
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-08-08 20:09, hash: 4c26bb0232
Worked: An older daily build from about a week ago, also 2.93
Caused by 647a8bff06

Short description of error
Newest Blender master daily build immediately crashes when trying to edit the attached test mesh. Also the shading on it in edit mode appears broken. None of these problems are present in Blender 2.93 from distro repo.

Exact steps for others to reproduce the error

Open the attached Blend-file edit crash 1.blend
In edit mode, select 2 or more vertices on the mesh
Press J to connect them through an edge

Alternatively:
2. In edit mode, select all vertices / faces
3. Use Mesh > Normals > Flip

Alternatively also:

Import the attached OBJ-file edit crash 1.obj into a new document
Apply the same editing steps

Additional info
The problematic mesh was extracted from a bigger document, but even after appending only the mesh data or exporting it as OBJ or FBX, importing and saving into a new document all through Blender 2.93, the crash is still reproducible in 3.0. Strangely, I'm not able to reproduce a crash or the shading issues if I start from a new document and edit a cube or poly plane into the same shape.

I disabled all add-ons that could have interfered, tried the Cycles-X branch build from yesterday and ran Blender both on the integrated and on the dedicated GPU through prime-run on this laptop, but the outcome is always the same.

The generated crash log is also attached.

edit crash 1.crash.txt

edit crash 1.obj

edit crash 1.blend

**System Information** Operating system: Linux-5.10.55-1-MANJARO-x86_64-with-glibc2.33 64 Bits Graphics card: Mesa DRI Intel(R) HD Graphics 4600 (HSW GT2) Intel Open Source Technology Center 4.5 (Core Profile) Mesa 21.1.6 **Blender Version** Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-08-08 20:09, hash: `4c26bb0232` Worked: An older daily build from about a week ago, also 2.93 Caused by 647a8bff06 **Short description of error** Newest Blender master daily build immediately crashes when trying to edit the attached test mesh. Also the shading on it in edit mode appears broken. None of these problems are present in Blender 2.93 from distro repo. **Exact steps for others to reproduce the error** 1. Open the attached Blend-file edit crash 1.blend 2. In edit mode, select 2 or more vertices on the mesh 3. Press J to connect them through an edge Alternatively: 2. In edit mode, select all vertices / faces 3. Use Mesh > Normals > Flip Alternatively also: 1. Import the attached OBJ-file edit crash 1.obj into a new document 2. Apply the same editing steps **Additional info** The problematic mesh was extracted from a bigger document, but even after appending only the mesh data or exporting it as OBJ or FBX, importing and saving into a new document all through Blender 2.93, the crash is still reproducible in 3.0. Strangely, I'm not able to reproduce a crash or the shading issues if I start from a new document and edit a cube or poly plane into the same shape. I disabled all add-ons that could have interfered, tried the Cycles-X branch build from yesterday and ran Blender both on the integrated and on the dedicated GPU through `prime-run` on this laptop, but the outcome is always the same. The generated crash log is also attached. [edit crash 1.crash.txt](https://archive.blender.org/developer/F10274746/edit_crash_1.crash.txt) [edit crash 1.obj](https://archive.blender.org/developer/F10274747/edit_crash_1.obj) [edit crash 1.blend](https://archive.blender.org/developer/F10274748/edit_crash_1.blend)

Added subscriber: @Snudl

#90538 was marked as duplicate of this issue

Added subscriber: @PratikPB2123

Thanks for creating a separate report.

Notes for those who is watching this issue for the first time.

The first bad commit I found is 647a8bff06
Possibly crash does not happen on debug build (at least on lite build)
Similar issue was reported here closed due to lack of information: #90489

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

I've got a fix for this, updating comments and checking other bugs in this area before committing.

This issue was referenced by 909e0819ae

Changed status from 'Confirmed' to: 'Resolved'

Added subscriber: @borschberry

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Seg fault crash with various edit functions #90532