bmesh.types.Bmesh.faces.sort() crashes blender on windows only #51072

New Issue

Geoffrey Bantle · 2017-03-28T20:17:25+02:00

Geoffrey Bantle commented

2017-03-28 20:17:25 +02:00

System Information
Windows 7 Enterprise 64 bit

Blender Version
Works Blender 2.75a 64 bit official windows build
Broken Blender 2.78c 64 bit official windows build

Short description of error
According to blender python documentation you can assign the index of each face in a bmesh a value and then later use those values to sort the faces.

See

https:*docs.blender.org/api/2.78b/bmesh.types.html#bmesh.types.BMFace.index And https:*docs.blender.org/api/2.78b/bmesh.types.html#bmesh.types.BMFaceSeq.sort

In the file this_file_crashes.blend is a script, run_me. It assigns each face in a subdivided cube a unique, non-negative index. After calling bmesh.types.Bmesh.faces.sort() blender crashes with the message:

Error: EXCEPTION_ACCESS_VIOLATION

This error has been reproduced on 4 separate windows systems. Several linux machines have been tested but the error does not occur there.

Steps to reproduce

Open Blender v2.78c 64 bit on windows.
Open the file this_file_crashes.blend
Run the script run_me
Blender should crash

Also

Open Blender v2.75a 64 bit on windows
Open the file this_file_crashes.blend
Run the script run_me
Blender should not crash

Finally

Open Blender v2.78c 64 bit on windows.
Open the file this_file_does_not_crash.blend
Run the script run_me
Blender should not crash

this_file_crashes.blend

this_file_does_not_crash.blend
The only difference between the scripts in the two blend files is the call to bmesh.types.Bmesh.faces.sort()

**System Information** Windows 7 Enterprise 64 bit **Blender Version** *Works* Blender 2.75a 64 bit official windows build *Broken* Blender 2.78c 64 bit official windows build **Short description of error** According to blender python documentation you can assign the index of each face in a bmesh a value and then later use those values to sort the faces. *See* [[ https:*docs.blender.org/api/2.78b/bmesh.types.html#bmesh.types.BMFace.index ]]*And*[[ https:*docs.blender.org/api/2.78b/bmesh.types.html#bmesh.types.BMFaceSeq.sort ]] In the file *this_file_crashes.blend* is a script, *run_me*. It assigns each face in a subdivided cube a unique, non-negative index. After calling bmesh.types.Bmesh.faces.sort() blender crashes with the message: > Error: EXCEPTION_ACCESS_VIOLATION This error has been reproduced on 4 separate windows systems. Several linux machines have been tested but the error does not occur there. **Steps to reproduce** - Open Blender v2.78c 64 bit on windows. - Open the file *this_file_crashes.blend* - Run the script *run_me* - Blender should crash *Also* - Open Blender v2.75a 64 bit on windows - Open the file *this_file_crashes.blend* - Run the script *run_me* - Blender should not crash *Finally* - Open Blender v2.78c 64 bit on windows. - Open the file *this_file_does_not_crash.blend* - Run the script *run_me* - Blender should not crash [this_file_crashes.blend](https://archive.blender.org/developer/F526691/this_file_crashes.blend) [this_file_does_not_crash.blend](https://archive.blender.org/developer/F526692/this_file_does_not_crash.blend) The only difference between the scripts in the two blend files is the call to bmesh.types.Bmesh.faces.sort()

Geoffrey Bantle commented

2017-03-28 20:17:25 +02:00

Changed status to: 'Open'

Geoffrey Bantle commented

2017-03-28 20:17:25 +02:00

Added subscriber: @gbantle-3

Germano Cavalcante commented

2017-03-28 22:51:42 +02:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2017-03-28 22:51:42 +02:00

Interesting that when putting del(face) before bm.faces.sort(), the crash does not occur.
This implies that bm.free() does not invalidate the previously referenced faces. And the dealloc tries to read a self->bm that no longer exists.

Interesting that when putting `del(face)` before `bm.faces.sort()`, the crash does not occur. This implies that bm.free() does not invalidate the previously referenced faces. And the dealloc tries to read a self->bm that no longer exists.

Geoffrey Bantle commented

2017-03-28 23:15:51 +02:00

That makes sense. Could this be the source of the problem?

bm_mesh_remap_cd_update(&(*fap)->head, &new_fap->head, cd_poly_pyptr);

in bmesh_mesh.c at line 1636.

It looks to me like that might be where the python face is copied over to a new one after the sort and left dangling.

That makes sense. Could this be the source of the problem? > bm_mesh_remap_cd_update(&(*fap)->head, &new_fap->head, cd_poly_pyptr); in *bmesh_mesh.c* at line *1636*. It looks to me like that might be where the python face is copied over to a new one after the sort and left dangling.

Germano Cavalcante commented

2017-03-29 02:05:03 +02:00

In #51072#425197, @gbantle-3 wrote:
That makes sense. Could this be the source of the problem?

bm_mesh_remap_cd_update(&(*fap)->head, &new_fap->head, cd_poly_pyptr);

in bmesh_mesh.c at line 1636.

It looks to me like that might be where the python face is copied over to a new one after the sort and left dangling.

Yes you are right. And it seems to be related to 9304df5182

The reference of a pyobject may be being overwritten in bm_mesh_remap_cd_update and set to NULL :\

> In #51072#425197, @gbantle-3 wrote: > That makes sense. Could this be the source of the problem? > >> bm_mesh_remap_cd_update(&(*fap)->head, &new_fap->head, cd_poly_pyptr); > > in *bmesh_mesh.c* at line *1636*. > > It looks to me like that might be where the python face is copied over to a new one after the sort and left dangling. Yes you are right. And it seems to be related to 9304df5182 The reference of a pyobject may be being overwritten in `bm_mesh_remap_cd_update` and set to NULL :\

Campbell Barton was assigned by Germano Cavalcante

2017-03-29 08:09:22 +02:00

Germano Cavalcante commented

2017-03-29 08:09:22 +02:00

@ideasman42 Here is a possible solution -> D2587

@ideasman42 Here is a possible solution -> [D2587](https://archive.blender.org/developer/D2587)

Steffen Dünner commented

2017-03-29 16:48:02 +02:00

Added subscriber: @SteffenD

blender-admin commented

2017-03-31 06:01:16 +02:00

This issue was referenced by d097c2a1b3

This issue was referenced by d097c2a1b3155bf287abf72d56e1ab3a57b8b870

Germano Cavalcante commented

2017-03-31 08:53:51 +02:00

Changed status from 'Open' to: 'Resolved'

Germano Cavalcante closed this issue

2017-03-31 08:53:51 +02:00

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bmesh.types.Bmesh.faces.sort() crashes blender on windows only #51072