EnumProperty with ENUM_FLAG causes a crash #84889

New Issue

Rafael Navega · 2021-01-20T08:27:51+01:00

Rafael Navega commented

2021-01-20 08:27:51 +01:00

System Information
Operating system: Windows 8.1 x64
Graphics card: Intel HD Graphics 520

Blender Version
Broken: Blender 2.91.0, Commit date: 2020-11-18 18:54, Hash ad58999b0d
Worked: 2.90 (and below).

Additional files
blender.crash.txt is attached to this report.

Short description of error
Blender crashes when you click on the cells of an bpy.props.EnumProperty created with the ENUM_FLAG flag.

Exact steps for others to reproduce the error
On a Text Editor view, create a new text datablock, paste the following script and run it.
It will create an EnumProperty and draw it on the 3D View header.
Clicking on any of its cells crashes Blender.

import bpy
from time import time


def myCustomEnumDrawHeader(self, context):
    layout = self.layout.row(align=True)
    layout.alignment = 'CENTER'
    layout.prop(context.scene, 'myCustomEnum', expand=True, icon_only=True)


def myCustomEnumItems(self, context):
    items = [
        (
            str(index), # String identifier.
            str(index), # UI label.
            '', # UI description.
            'LAYER_ACTIVE',
            2**index # Integer index (always a power-of-two with the 'ENUM_FLAG' option).
        )
        for index in range(9)
    ]
    return items


def myCustomEnumGet(self):
    return 2 ** 3


def myCustomEnumSet(self, value):
    print('myCustomEnumSet()', int(time.time() * 1000))
    

def register():
    bpy.types.Scene.myCustomEnum = bpy.props.EnumProperty(
        name = '',
        items = myCustomEnumItems,
        get = myCustomEnumGet,
        set = myCustomEnumSet,
        description = 'My Custom Enum',
        options = {'ENUM_FLAG', 'SKIP_SAVE', 'HIDDEN'}
    )
    bpy.types.VIEW3D_HT_header.append(myCustomEnumDrawHeader)


def unregister():
    bpy.types.VIEW3D_HT_header.remove(myCustomEnumDrawHeader)
    del bpy.types.Scene.myCustomEnum
    

if __name__ == "__main__":
    register()

{F9588970}

**System Information** Operating system: Windows 8.1 x64 Graphics card: Intel HD Graphics 520 **Blender Version** Broken: Blender 2.91.0, Commit date: 2020-11-18 18:54, Hash ad58999b0d46 Worked: 2.90 (and below). **Additional files** blender.crash.txt is attached to this report. **Short description of error** Blender crashes when you click on the cells of an `bpy.props.EnumProperty` created with the `ENUM_FLAG` flag. **Exact steps for others to reproduce the error** On a Text Editor view, create a new text datablock, paste the following script and run it. It will create an EnumProperty and draw it on the 3D View header. Clicking on any of its cells crashes Blender. ``` import bpy from time import time def myCustomEnumDrawHeader(self, context): layout = self.layout.row(align=True) layout.alignment = 'CENTER' layout.prop(context.scene, 'myCustomEnum', expand=True, icon_only=True) def myCustomEnumItems(self, context): items = [ ( str(index), # String identifier. str(index), # UI label. '', # UI description. 'LAYER_ACTIVE', 2**index # Integer index (always a power-of-two with the 'ENUM_FLAG' option). ) for index in range(9) ] return items def myCustomEnumGet(self): return 2 ** 3 def myCustomEnumSet(self, value): print('myCustomEnumSet()', int(time.time() * 1000)) def register(): bpy.types.Scene.myCustomEnum = bpy.props.EnumProperty( name = '', items = myCustomEnumItems, get = myCustomEnumGet, set = myCustomEnumSet, description = 'My Custom Enum', options = {'ENUM_FLAG', 'SKIP_SAVE', 'HIDDEN'} ) bpy.types.VIEW3D_HT_header.append(myCustomEnumDrawHeader) def unregister(): bpy.types.VIEW3D_HT_header.remove(myCustomEnumDrawHeader) del bpy.types.Scene.myCustomEnum if __name__ == "__main__": register() ``` {F9588970}

Rafael Navega commented

2021-01-20 08:27:51 +01:00

Added subscriber: @RNavega

Rafael Navega commented

2021-01-20 08:29:14 +01:00

blender.crash.txt:

blender.crash.txt

blender.crash.txt: [blender.crash.txt](https://archive.blender.org/developer/F9588975/blender.crash.txt)

Philipp Oeser commented

2021-01-20 09:46:18 +01:00

Added subscriber: @lichtwerk

Philipp Oeser commented

2021-01-20 09:46:18 +01:00

No crash here

**System Information**
Operating system: Linux-5.9.16-200.fc33.x86_64-x86_64-with-fedora-33-Thirty_Three 64 Bits
Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 455.45.01
version: 2.93.0 Alpha, branch: master, commit date: 2021-01-19 17:40, hash: `rB02a63115d25f`, tested 2.91 as well

No crash here ``` **System Information** Operating system: Linux-5.9.16-200.fc33.x86_64-x86_64-with-fedora-33-Thirty_Three 64 Bits Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 455.45.01 version: 2.93.0 Alpha, branch: master, commit date: 2021-01-19 17:40, hash: `rB02a63115d25f`, tested 2.91 as well ```

Robert Guetzkow commented

2021-01-20 09:53:57 +01:00

Added subscriber: @rjg

Robert Guetzkow commented

2021-01-20 09:53:57 +01:00

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

Robert Guetzkow closed this issue

2021-01-20 09:53:57 +01:00

Robert Guetzkow commented

2021-01-20 09:53:57 +01:00

The EnumProperty is a bit more complicated to use. You are required to keep a reference to the values returned by the callback assigned to items. This is documented in the manual:

There is a known bug with using a callback, Python must keep a reference to the strings returned by the callback or Blender will misbehave or even crash.

This means you have to modify your script, so that each call to myCustomEnumItems stores the resulting value in a variable, thus keeping a reference. For a similar issue see blender/blender-addons#83360 and the fix blender/blender-addons@cef282cc9a.

The `EnumProperty` is a bit more complicated to use. You are required to keep a reference to the values returned by the callback assigned to `items`. This is documented in the manual: > There is a known bug with using a callback, Python must keep a reference to the strings returned by the callback or Blender will misbehave or even crash. This means you have to modify your script, so that each call to `myCustomEnumItems` stores the resulting value in a variable, thus keeping a reference. For a similar issue see blender/blender-addons#83360 and the fix blender/blender-addons@cef282cc9a.

Rafael Navega commented

2021-01-20 10:48:01 +01:00

@rjg Hi, can you advise on how to apply the fix to that example script above? Below you can find a modified version that keeps a reference, but it still crashes in the same way. The change is in myCustomEnumItems:

Crash file:
blender.crash.txt

import bpy


def myCustomEnumDrawHeader(self, context):
    layout = self.layout.row(align=True)
    layout.alignment = 'CENTER'
    layout.prop(context.scene, 'myCustomEnum', expand=True, icon_only=True)


myItems = [ ]

def myCustomEnumItems(self, context):
    global myItems
    myItems.clear()
    myItems.extend(
        (
            str(index), # String identifier.
            str(index), # UI label.
            '', # UI description.
            'LAYER_ACTIVE',
            2**index # Integer index (always a power-of-two with the 'ENUM_FLAG' option).
        )
        for index in range(9)
    )
    return myItems


def myCustomEnumGet(self):
    return 2 ** 3


def myCustomEnumSet(self, value):
    print('myCustomEnumSet()')
    

def register():
    bpy.types.Scene.myCustomEnum = bpy.props.EnumProperty(
        name = '',
        items = myCustomEnumItems,
        get = myCustomEnumGet,
        set = myCustomEnumSet,
        description = 'My Custom Enum',
        options = {'ENUM_FLAG', 'SKIP_SAVE', 'HIDDEN'}
    )
    bpy.types.VIEW3D_HT_header.append(myCustomEnumDrawHeader)


def unregister():
    bpy.types.VIEW3D_HT_header.remove(myCustomEnumDrawHeader)
    del bpy.types.Scene.myCustomEnum
    

if __name__ == "__main__":
    register()

@rjg Hi, can you advise on how to apply the fix to that example script above? Below you can find a modified version that keeps a reference, but it still crashes in the same way. The change is in `myCustomEnumItems`: Crash file: [blender.crash.txt](https://archive.blender.org/developer/F9589104/blender.crash.txt) ``` import bpy def myCustomEnumDrawHeader(self, context): layout = self.layout.row(align=True) layout.alignment = 'CENTER' layout.prop(context.scene, 'myCustomEnum', expand=True, icon_only=True) myItems = [ ] def myCustomEnumItems(self, context): global myItems myItems.clear() myItems.extend( ( str(index), # String identifier. str(index), # UI label. '', # UI description. 'LAYER_ACTIVE', 2**index # Integer index (always a power-of-two with the 'ENUM_FLAG' option). ) for index in range(9) ) return myItems def myCustomEnumGet(self): return 2 ** 3 def myCustomEnumSet(self, value): print('myCustomEnumSet()') def register(): bpy.types.Scene.myCustomEnum = bpy.props.EnumProperty( name = '', items = myCustomEnumItems, get = myCustomEnumGet, set = myCustomEnumSet, description = 'My Custom Enum', options = {'ENUM_FLAG', 'SKIP_SAVE', 'HIDDEN'} ) bpy.types.VIEW3D_HT_header.append(myCustomEnumDrawHeader) def unregister(): bpy.types.VIEW3D_HT_header.remove(myCustomEnumDrawHeader) del bpy.types.Scene.myCustomEnum if __name__ == "__main__": register() ```

Rafael Navega commented

2021-01-20 11:06:28 +01:00

Okay, this is interesting, since the crash is happening with a Windows build and as @lichtwerk said they couldn't reproduce the crash, I'm thinking this might be a Windows-only issue since the stacktrace has the crash happening with function strchr of VCRUNTIME140.dll.

For completeness, I also did another test with a static list defined as a global variable so it's never lost, but the problem persists, check it out:

import bpy


def myCustomEnumDrawHeader(self, context):
    layout = self.layout.row(align=True)
    layout.alignment = 'CENTER'
    layout.prop(context.scene, 'myCustomEnum', expand=True, icon_only=True)


myItems = [
    ('1', '1', '', 'LAYER_ACTIVE', 1),
    ('2', '2', '', 'LAYER_ACTIVE', 2),
    ('3', '3', '', 'LAYER_ACTIVE', 4),
    ('4', '4', '', 'LAYER_ACTIVE', 8),
]

def myCustomEnumItems(self, context):
    print('myCustomEnumItems()')
    global myItems
    return myItems
    

myValue = 0

def myCustomEnumGet(self):
    print('myCustomEnumGet()')
    global myValue
    return myValue


def myCustomEnumSet(self, value):
    print('myCustomEnumSet()', value)
    global myValue    
    myValue = value
    

def register():
    bpy.types.Scene.myCustomEnum = bpy.props.EnumProperty(
        name = '',
        items = myCustomEnumItems,
        get = myCustomEnumGet,
        set = myCustomEnumSet,
        description = 'My Custom Enum',
        options = {'ENUM_FLAG', 'SKIP_SAVE', 'HIDDEN'}
    )
    bpy.types.VIEW3D_HT_header.append(myCustomEnumDrawHeader)


def unregister():
    bpy.types.VIEW3D_HT_header.remove(myCustomEnumDrawHeader)
    del bpy.types.Scene.myCustomEnum
    

if __name__ == "__main__":
    register()

Okay, this is interesting, since the crash is happening with a Windows build and as @lichtwerk said they couldn't reproduce the crash, I'm thinking this might be a Windows-only issue since the stacktrace has the crash happening with function `strchr` of `VCRUNTIME140.dll`. For completeness, I also did another test with a static list defined as a global variable so it's never lost, but the problem persists, check it out: ``` import bpy def myCustomEnumDrawHeader(self, context): layout = self.layout.row(align=True) layout.alignment = 'CENTER' layout.prop(context.scene, 'myCustomEnum', expand=True, icon_only=True) myItems = [ ('1', '1', '', 'LAYER_ACTIVE', 1), ('2', '2', '', 'LAYER_ACTIVE', 2), ('3', '3', '', 'LAYER_ACTIVE', 4), ('4', '4', '', 'LAYER_ACTIVE', 8), ] def myCustomEnumItems(self, context): print('myCustomEnumItems()') global myItems return myItems myValue = 0 def myCustomEnumGet(self): print('myCustomEnumGet()') global myValue return myValue def myCustomEnumSet(self, value): print('myCustomEnumSet()', value) global myValue myValue = value def register(): bpy.types.Scene.myCustomEnum = bpy.props.EnumProperty( name = '', items = myCustomEnumItems, get = myCustomEnumGet, set = myCustomEnumSet, description = 'My Custom Enum', options = {'ENUM_FLAG', 'SKIP_SAVE', 'HIDDEN'} ) bpy.types.VIEW3D_HT_header.append(myCustomEnumDrawHeader) def unregister(): bpy.types.VIEW3D_HT_header.remove(myCustomEnumDrawHeader) del bpy.types.Scene.myCustomEnum if __name__ == "__main__": register() ```

Robert Guetzkow commented

2021-01-20 11:20:22 +01:00

@RNavega I will take another look at this shortly.

Robert Guetzkow commented

2021-01-20 11:43:43 +01:00

Changed status from 'Archived' to: 'Resolved'

Robert Guetzkow commented

2021-01-20 11:43:43 +01:00

The issue you're having should be fixed by 256e77c987. You aren't using the official release version of 2.91.0 from November 25 that contains the fix, please install the official release.

You still need to keep a reference to the items though as I've said in my initial comment.

The issue you're having should be fixed by 256e77c987. You aren't using the official release version of [2.91.0 ](https://download.blender.org/release/Blender2.91/) from November 25 that contains the fix, please install the official release. You still need to keep a reference to the `items` though as I've said in my initial comment.

Rafael Navega commented

2021-01-21 07:57:14 +01:00

@rjg it's working great on 2.91 from November 25 and up. And I will keep a reference to the dynamic EnumProperty items as recommended.

Thank you very much for your time!

@rjg it's working great on 2.91 from November 25 and up. And I will keep a reference to the dynamic EnumProperty items as recommended. Thank you very much for your time!

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EnumProperty with ENUM_FLAG causes a crash #84889