Crash with new Datablock ID Properties #51198

New Issue

Simon Wendsche · 2017-04-13T15:17:54+02:00

Simon Wendsche commented

2017-04-13 15:17:54 +02:00

Short description of error
Blender crashes when an object with the new Datablock ID Properties a7b3047cef references itself or when two objects reference each other.

Exact steps for others to reproduce the error

Open default scene (Camera, Cube, Lamp) or use the attached .blend
Run this script:

import bpy

bpy.types.Object.prop = bpy.props.PointerProperty(type=bpy.types.Object)

cube = bpy.data.objects['Cube']
lamp = bpy.data.objects['Lamp']
camera = bpy.data.objects['Camera']

# init the props so we can edit them in the Custom Properties panel
cube.prop = camera
lamp.prop = camera

Now this scene can lead to two crashes I discovered so far:
Crash 1:
select cube, choose Lamp from prop dropdown in Custom Properties
select lamp, choose Cube from prop dropdown in Custom Properties
crash
Crash 2:
select cube, choose Cube from prop dropdown in Custom Properties
crash

Edit: Important detail I forgot:
It only happens when setting the prop value by hand, not when it is done in Python.
The Python script can't trigger the crash, for example this line works (while it crashes when done by hand):

cube.prop = cube

System Information
Linux 64 bit (Ubuntu 14.04)

Blender Version
Broken: 2.78 575d641 (says the splashscreen, I built from Blender master, so it's 2.79dev)

datablock_crash.blend

**Short description of error** Blender crashes when an object with the new [Datablock ID Properties ](https://developer.blender.org/D113) a7b3047cefcb references itself or when two objects reference each other. **Exact steps for others to reproduce the error** * Open default scene (Camera, Cube, Lamp) or use the attached .blend * Run this script: ``` import bpy bpy.types.Object.prop = bpy.props.PointerProperty(type=bpy.types.Object) cube = bpy.data.objects['Cube'] lamp = bpy.data.objects['Lamp'] camera = bpy.data.objects['Camera'] # init the props so we can edit them in the Custom Properties panel cube.prop = camera lamp.prop = camera ``` * Now this scene can lead to two crashes I discovered so far: * Crash 1: * select cube, choose Lamp from prop dropdown in Custom Properties * select lamp, choose Cube from prop dropdown in Custom Properties * crash * Crash 2: * select cube, choose Cube from prop dropdown in Custom Properties * crash **Edit: Important detail I forgot:** It only happens when setting the prop value by hand, not when it is done in Python. The Python script can't trigger the crash, for example this line works (while it crashes when done by hand): ``` cube.prop = cube ``` **System Information** Linux 64 bit (Ubuntu 14.04) **Blender Version** Broken: 2.78 575d641 (says the splashscreen, I built from Blender master, so it's 2.79dev)![scrn_13-04-2017_15-16-32.png](https://archive.blender.org/developer/F544485/scrn_13-04-2017_15-16-32.png) [datablock_crash.blend](https://archive.blender.org/developer/F544487/datablock_crash.blend)

Simon Wendsche commented

2017-04-13 15:17:54 +02:00

Changed status to: 'Open'

Simon Wendsche commented

2017-04-13 15:17:54 +02:00

Added subscriber: @BYOB

Steffen Dünner commented

2017-04-13 15:51:39 +02:00

Added subscriber: @SteffenD

mathieu menuet commented

2017-04-13 19:10:44 +02:00

Added subscriber: @bliblubli

Alexander Romanov was assigned by mathieu menuet

2017-04-13 19:11:36 +02:00

Aaron Carlisle commented

2017-04-13 21:38:44 +02:00

Added subscriber: @mont29

Alexander Romanov commented

2017-04-14 10:39:54 +02:00

I've found the reason for this crash, and also found forward compatibility issue. I'm working on it.

Alexander Romanov commented

2017-04-14 15:10:47 +02:00

The reason of crash is infinite recursion, which happens in RNA_pointer_as_string.
I've also found python crash if you will try to remove the custom property pressing "-" button.
This is my solution for these two issues: P464

And one issue with forward compatibility, which I couldn't solve yet:
crash inside

PropertyType RNA_property_type(PropertyRNA *prop)
{
	return rna_ensure_property(prop)->type;
}

rna_ensure_property always returns NULL for IDP_ID for Blender builds before D113. This crash happens for me only when I'm opening "Custom Properties" panel.
@mont29, could you help please?

The reason of crash is infinite recursion, which happens in RNA_pointer_as_string. I've also found python crash if you will try to remove the custom property pressing "-" button. This is my solution for these two issues: [P464](https://archive.blender.org/developer/P464.txt) And one issue with forward compatibility, which I couldn't solve yet: crash inside ``` PropertyType RNA_property_type(PropertyRNA *prop) { return rna_ensure_property(prop)->type; } ``` rna_ensure_property always returns NULL for IDP_ID for Blender builds before [D113](https://archive.blender.org/developer/D113). This crash happens for me only when I'm opening "Custom Properties" panel. @mont29, could you help please?

Alexander Romanov commented

2017-04-14 19:54:59 +02:00

Possible solution for forward compatibility issue: P465

Possible solution for forward compatibility issue: [P465](https://archive.blender.org/developer/P465.txt)

Bastien Montagne commented

2017-04-18 17:03:39 +02:00

Added subscribers: @Sergey, @ideasman42

Bastien Montagne commented

2017-04-18 17:03:39 +02:00

@AlexanderRomanov mostly fine with P464 (rna part of it at least, not convinced by python changes there).

But P465 is a no-go for me, imho it is totally unacceptable to twist that way our .blend file just to ensure forward compat (not to mention how evil it is to change actual data, even if only for a few micro seconds, in writefile!). I’m tempted to consider this a bug in previous blender (if a function can return NULL and is not checked, then bug is in code using it). Can only think about protecting against this for future (e.g. by nuking IDProps of unknown type at read time, keeping them around is call for issues anyway at some point)… Would not mind @Sergey or @ideasman42 input here though.

@AlexanderRomanov mostly fine with [P464](https://archive.blender.org/developer/P464.txt) (rna part of it at least, not convinced by python changes there). But [P465](https://archive.blender.org/developer/P465.txt) is a no-go for me, imho it is totally unacceptable to twist that way our .blend file just to ensure forward compat (not to mention how evil it is to change actual data, even if only for a few micro seconds, in writefile!). I’m tempted to consider this a bug in previous blender (if a function can return NULL and is not checked, then bug is in code using it). Can only think about protecting against this for future (e.g. by nuking IDProps of unknown type at read time, keeping them around is call for issues anyway at some point)… Would not mind @Sergey or @ideasman42 input here though.

Alexander Romanov commented

2017-04-18 18:06:12 +02:00

@mont29 for first part of P464 I've recorded the video: https://youtu.be/jF0CtWQPsC4

@mont29 for first part of [P464](https://archive.blender.org/developer/P464.txt) I've recorded the video: https://youtu.be/jF0CtWQPsC4

Bastien Montagne commented

2017-04-19 09:57:02 +02:00

@AlexanderRomanov aaaah oki, see the issue now. But this -remove property' button makes absolutely no sense for API-defined IDProps! Nuked it in 42c8d93c5f. ;)

So you can commit the RNA part of P464.

For the forward compat issue, we need advice from other devs. ;)

@AlexanderRomanov aaaah oki, see the issue now. But this -remove property' button makes absolutely no sense for API-defined IDProps! Nuked it in 42c8d93c5f. ;) So you can commit the RNA part of [P464](https://archive.blender.org/developer/P464.txt). For the forward compat issue, we need advice from other devs. ;)

Sergey Sharybin commented

2017-04-19 10:22:05 +02:00

@mont29, we indeed should not modify anything from the main database during file save. This was known for giving issues in the past. What i remember happening at some point is that we were constructing temp copy of the objects and made modifications on those. Need to be careful tho, because that will modify pointers of the struct itself.

Bastien Montagne commented

2017-04-19 11:07:15 +02:00

@Sergey yes, temp structs is the way to go here - while keeping orig pointer one as 'uuid' (pointer value in file), to ensure re-allocating temp memory later in write process does not re-use same mem pointer…

But that’s not the main issue here, main issue is that P465 horribly tweaks IDProps to save them in a way that new pointer IDProps do not make older blender crash when loading a file saved with those new properties. Imho this is not really acceptable, especially since the root of the issue remains - should we introduce a new IDProp type in the future, it will again make older Blender crash. So to me this is a bug in current code, that is trivial to fix (e.g. by removing any unknown IDProp type at read time), but we should not try to fix this for previous versions… As ugly as it is :(

@Sergey yes, temp structs is the way to go here - while keeping orig pointer one as 'uuid' (pointer value in file), to ensure re-allocating temp memory later in write process does not re-use same mem pointer… But that’s not the main issue here, main issue is that [P465](https://archive.blender.org/developer/P465.txt) horribly tweaks IDProps to save them in a way that new pointer IDProps do not make older blender crash when loading a file saved with those new properties. Imho this is not really acceptable, especially since the root of the issue remains - should we introduce a new IDProp type in the future, it will again make older Blender crash. So to me this is a bug in current code, that is trivial to fix (e.g. by removing any unknown IDProp type at read time), but we should not try to fix this for previous versions… As ugly as it is :(

blender-admin commented

2017-04-20 10:39:20 +02:00

This issue was referenced by 31c644b657

This issue was referenced by 31c644b657d3dbfaa170e5893fcd69ea5b87d670

Alexander Romanov commented

2017-04-20 10:40:34 +02:00

Changed status from 'Open' to: 'Resolved'

Alexander Romanov closed this issue

2017-04-20 10:40:34 +02:00

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Crash with new Datablock ID Properties #51198