Nuget, IL2CPP, native libs

I fell into a quagmire trying to get SQLite-net and SQLiteNetExtensions working with IL2CPP on Mac.

There's a lot of complexity there. Extensions -> SQLite-net -> SQLitePCL.raw -> SQLite provider -> (e_)sqlite3.

It was all working fine with mono. But in IL2CPP, it can't find the native library. I'm not sure if it's the Mono bug related to the library file extensions (.dylib vs .so: I tried both), or if it's looking in the wrong directory (I tried a lot of places, inside the app bundle and in my home folder), or if it's being blocked somehow. I tried renaming e_sqlite3.dylib to e_squlite3.bundle and putting it into the plugins folder.

I'm facing a number of obstacles to understanding it and solving it. I don't know how to debug the built player. I don't understand the interactions between libraries and il2cpp. the SQLitePCL libs are supposed to be cross-platform. Unfortunately, the SQLitePCL.raw library does a lot of magic code generation, so it's not even easy to read the code.

Are all the mono libraries converted into C++ at build time? Or are there pre-compiled versions of them, to avoid that redundant effort at build time?

Is there a general way to get various C# libraries to work with Unity even if they weren't designed with that in mind? Or do they have to be aware of Unity or mono or something to work properly?

What if I wanted to access other C libraries built into Mac or iOS? What if there are already C# wrappers for that? Is there a standard path to make them available to Unity? Will they work with il2cpp? How do I learn more details about the interoperability and dependencies of these tools?

I've already read all the manual pages about il2cpp and native plugins. I've even written a simple native plugin at one time, and was able to access native Objective-C frameworks. But mixing in existing C# libraries seems to lead to incompatibilities.

 

About a week ago there was a discussion in here about mixing C++ and CLI and other stuff. Check around in the pages just beyond this. I forget the exact title, and I'm not sure it is 100% relevant, but it rang a bell, and if I recall the guy wrote up a pretty good final summary of what he did.

As for your actual problem, have you taken a look through the Unity asset store? There are several assets in there dealing with SQLite and some of them may already pre-integrate the extensions you're talking about. I know very little about SQL under Unity in general, but last year under Unity2017-something I used this package:

https://github.com/codecoding/SQLite4Unity3d

for read-only access to a binary-included database we put into Streaming Assets, and the entire process just worked, cross platform iOS (IL2CPP) and Android and PC, so that's also something to look at.

EDIT: this is the post I mentioned in the first para:

https://forum.unity.com/threads/is-c-cli-forbidden-in-unity.700115/

 

@Kurt-Dekker thanks for the pointer. I read through it. It's interesting, although not directly related. Any info that gives me a deeper understanding of the build and runtime systems is appreciated, at least so I can make more progress and ask more intelligible/informed questions.

 

Anybody knows how to integrate .cpp files directly in IL2CPP back-end in Windows?

 

I read that page but I couldn't make it work, when I build a player it always fails.
I filed a bug report.

Failed running C:\Program Files\Unity 2020.1.0a12\Editor\Data\il2cpp/build/deploy/net471/il2cpp.exe --convert-to-cpp --emit-null-checks --enable-array-bounds-check --dotnetprofile="unityaot" --compile-cpp --libil2cpp-static --platform="WindowsDesktop" --architecture="x86" --configuration="Release" --outputpath="C:\Users\HP\Documents\Unity Projects\C11\Temp/StagingArea/Data\Native\GameAssembly.dll" --cachedirectory="C:\Users\HP\Documents\Unity Projects\C11\Assets\..\Library/il2cpp_cache" --incremental-g-c-time-slice=3 --profiler-report --map-file-parser="C:/Program Files/Unity 2020.1.0a12/Editor/Data/Tools/MapFileParser/MapFileParser.exe" --directory="C:/Users/HP/Documents/Unity Projects/C11/Temp/StagingArea/Data/Managed" --generatedcppdir="C:/Users/HP/Documents/Unity Projects/C11/Temp/StagingArea/Data/il2cppOutput"



stdout:

Building GameAssembly.dll with MsvcDesktopToolChain

   Msvc Install Version: 15.0

   Msvc Install SDK Directory: C:\Program Files (x86)\Windows Kits\10

   Msvc Linker Path: C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\bin\HostX64\x86\link.exe

   Msvc Compiler Path: C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.23.28105\bin\HostX64\x86\cl.exe



   Output directory: C:\Users\HP\Documents\Unity Projects\C11\Temp\StagingArea\Data\Native

   Cache directory: C:\Users\HP\Documents\Unity Projects\C11\Library\il2cpp_cache

il2cpp.exe didn't catch exception: Unity.IL2CPP.Building.BuilderFailedException: plug.c

C:\Users\HP\Documents\Unity Projects\C11\Temp\StagingArea\Data\il2cppOutput\plug.c(4): error C2059: syntax error: 'string'

 

@JoshPeterson I doubt it, I tried running a console app, here is 3 different versions I tried.

Code (CSharp):

1. // plug.c
2.  
3. #include <math.h>
4. #define EXPORT __stdcall __declspec(dllexport)
5.  
6. extern "C"{
7. /* Power function*/
8. EXPORT int power1(int n, int p)
9. {
10.     int r = pow(n, p);
11.     return r;
12. }
13.  
14. }

Code (CSharp):

1. #include <math.h>
2. #define EXPORT __stdcall __declspec(dllexport)
3.  
4.  
5. /* Power function*/
6. EXPORT int power1(int n, int p)
7. {
8.     int r = pow(n, p);
9.     return r;
10. }
11.  

Code (CSharp):

1. #include <math.h>
2. #define EXPORT __declspec(dllexport)
3.  
4.  
5. /* Power function*/
6. EXPORT int power1(int n, int p)
7. {
8.     int r = pow(n, p);
9.     return r;
10. }
11.  

None it works, also tried with `cpp` extension.

 

That was put in the Plugins folder;
Now the C# side:

Code (CSharp):

1.     [DllImport("__Internal", EntryPoint ="power1")] static extern int power1(int n, int p);
2.  

Even if I delete the calling C# code, I would still get the error.

I'm using 2020.1 alpha

 

@JoshPeterson I seem to have resolved the issue by building into a new folder instead of the same old one.
Maybe it was dirtied by something erroneous.

Rebuilding into the folder with a successful build doesn't reproduce the issue.

 

I think all is good now, can I take this chance to ask for Editor support of IL2CPP native source files.

 

Maybe Unity could automatically build the files into a dynamic link library like we currently do.
Anyway thanks for the support.

 

Would it be possible to unload the plugin so we can delete it or replace it without restarting the editor?