Explorer++ creates empty directories in places it visits

[AnyOldName3]

The problem:

Every directory I visit in Explorer++ via Explore Virtual Folder gains a subdirectory at Device\MMCSS in Overwrite.

To Reproduce:

Steps to reproduce the behavior:

1. Open MO2.
2. Click Explore Virtual Folder.
3. Visit a directory, e.g. Meshes\f.
4. Exit Explorer++.
5. Open the Overwrite mod.
6. Observe that there are new directories, e.g. Device\MMCSS, Meshes\Device\MMCSS and Meshes\f\Device\MMCSS.

Environment:

• Mod Organizer Version that exhibits the issue: 2.3.2
• Last Mod Organizer Verison that did not exhibit the issue (if applicable): Not tested.
• Desktop OS/version used to run Mod Organizer: Windows 10 18363.1016

Details:

The files don't show up in Explorer++ if you visit the folder again without restarting it.

Link to Mod Organizer logs:

Right click on the log window at the bottom of MO2, set log level to debug, restart Mo2 and reproduce the problem.
To access the log files you can press the Open folder icon over the modlist and select "Open MO2 Logs folder".

USVFS:

https://gist.github.com/AnyOldName3/6a6f21b9c75ea1eb0baeaf076ff3a188#file-usvfs-2020-09-08_22-32-11-log

I've not looked at this.

MO Interface:

https://gist.github.com/AnyOldName3/6a6f21b9c75ea1eb0baeaf076ff3a188#file-mo_interface-log

There's nothing fun in this.

[Al12rs]

We suspected this was caused by an unhandled Delete On Close flag used when creating those folders. Basically we aren't passing it through and closing doesn't delete the files.
Alternatively this could be a bug with the fake directory registry not cleaning up correctly.

[AnyOldName3]

I didn't know this was a known issue. I did search first, including closed ones too.

[Al12rs]

I thought we had something already too but I didn't find anything.

I had this issue too with MO 2.3.2. 1.35 or the new 1.40 version of Explorer++ are all having this problem.

Also, I tested it in win7, but it's fine in win7.

It only happened in win10.

Also, I've run Dism++ to optimize my win10. I don't know if that's relevant.

Also, it won't happen in other folders like C drive or other irrelevant folders, only in Skyrim's folder.

I also have a ASIO sound card installed. I don't know it's relevant or not but it seems that MMCSS is something related to audios.

I also tested in an win10 vm with sound card uninstalled but still the problem exists.

My assumption?

I think, that "Device\MMCSS" is a fake file in win10 system, but MO2 treats it as if it's real so that it create a folder like this.

So the solution might be just detect this kind of file access and stop it.

But it's still weird that it only happens with Explorer++

It means that, using Explorer++ solely or using MO2 solely are all fine, but they won't cooperate.

[isanae]

Well, I just hooked a debugger to it, and it has nothing to do with the delete on close flag. Something is trying to create a variety of files, such as \Device\DeviceApi\Dev\Query, \Device\MMCSS\MmThread, \Device\DeviceApi\CMNotify, etc. Some of them seem to part of PnP, others from the "Multimedia Class Scheduler Service".

Regardless, these files end up being rerouted. RerouteW::create() calls absolutePath() on these, which ends up in winapi::wide::getFullPathName(). This calls ::GetFullPathNameW(), which seems to consider these paths as relative and prepend the current drive and cwd to them. So they become something like C:\game\Data\Somewhere\Device\MMCSS\MmThread, which ends up being rerouted to overwrite and created as a fake path C:\Users\user\AppData\Local\ModOrganizer\instance\overwrite\Somewhere\Device\MMCSS.

I'm not sure about the fix. These paths are weird, they feel like pipes or something. I'd want to just forward them as-is, but I'd need to figure out how to recognize them.

Also I found out that even if I create a mod from the overwrite folder which contains the created "Device/MMCSS" folder, Explorer++ will still create such folders in overwrite next time. Can it be fixed so that we can put them in a mod folder and never show up in Overwrite again?