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: rB5314161491d4

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 T60491 which was closed because it couldn't be reproduced.

Exact steps for others to reproduce the error

1. Open the attached blend file
2. Run the script

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()