How to inject custom native libraries (like ntsync) into CrossOver?

[Alien4042x]

Hi everyone,

I'm currently working on modifying the ntsync library to run natively on macOS instead of Linux.
But I'm struggling to find a way to properly test it inside CrossOver, because CrossOver seems to always load its internal version of ntsync, ignoring any replacements I try inside the bottle.

I've compiled it as a .dlib and also tried building .dll versions, but no success so far.

Does anyone know how to override or hook internal CrossOver libraries like ntsync on macOS?
Any tips would be greatly appreciated!

Thanks!

[italomandara]

you still need a dll library in order to configure an override

[Alien4042x]

Thanks for the reply!

I actually did compile a .dll version already (not just a .dlib),
but CrossOver still ignores it.

I also tried setting up an override manually in winecfg, but it didn't seem to work.

I'm wondering if the problem might be that my DLL is not properly built as a PE/COFF binary,
or maybe I'm missing something else?

Would cross-compiling with mingw-w64 help in this case?

Thanks a lot for any advice!

[italomandara]

it could be because ntsync doesn't belong to windows.

ntsync.dll does not exist as a standard Windows DLL. It is a Linux kernel driver used for emulation of NT synchronization primitives, specifically for Wine (a compatibility layer for running Windows applications on Linux). It aims to provide a more accurate and robust implementation of synchronization mechanisms than previous approaches like "esync" and "fsync".

So probably that's the reason it fails this is uncharted territory for me TBH

[Alien4042x]

Yeah, I know. But same way as someone ported esync and replaced the pipeline, I’m trying something similar.
I used mutexes and other primitives for now, and injected it into Notepad via Whisky — worked fine.
Problem is, Whisky can't properly launch Steam for me (or maybe my drivers were missing), so now I’m trying to build a hybrid Wine Staging with D3DMetal to test it better.
But honestly, that's gonna take a lot of time — first, Gatekeeper keeps blocking me, and second, there are like 1000 lines of code that need to be rewritten.
CrossOver also doesn’t let me use export DYLD_INSERT_LIBRARIES=..., it just acts like the command doesn’t exist — so I can't test it there yet.

[italomandara]

have you checked how is done on msync?

[Alien4042x]

Soo. I compiled my own ntdll.so/ntdll.dll using arch -x86_64 zsh and ../configure --enable-win64 --without-freetype --prefix="$HOME/wine-install" --disable-tests && make, added a custom ntsync (not hooked in loader.c), and strangely got Steam overlay working and higher FPS, but completely broken Steam GUI — any idea why this happens, what flags might cause this, and also how to correctly build the 32-bit version (WoW64) after 64-bit is done?

I'm using also export PATH="/Users/xxxxx/llvm-mingw-20250430-ucrt-macos-universal/bin:$PATH" for llvmn

[italomandara]

Are you in the AppleGamingWiki discord? that could be an interesting conversation for the mac-developers channel, I'm sure we could get some good help from other devs.