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Windows Player: IL2CPP Scripting Backend

Use IL2CPP with Windows Player and add compatible C++ source code plug-ins to your build.
Read time 3 minutesLast updated 11 days ago
You can use IL2CPP as an alternative to Mono for scripting backend when building projects for Windows Player.
When you build a Project using IL2CPP, Unity converts IL code from scripts and assemblies to C++ before creating a native binary. See IL2CPP for more information.

C++ source code plugins for IL2CPP

You can add C++ (.cpp) code files directly into a Unity Project when using the IL2CPP scripting backend. The C++ files act as plugins within the Plugin Inspector. If you configure the C++ files to be compatible with Windows Player, Unity compiles them together with C++ code that gets generated from managed assemblies.
To view the plugin importer settings for C++ files, click a .cpp file and select the appropriate Windows option in the Platform settings section of the Inspector:

Plugin importer settings for C++ files

Because the functions are linked together with generated C++ code, there is no separate DLL to 
_P/Invoke
into. Due to this, you can use the 
“__Internal”
keyword in place of the DLL name, which makes it the C++ linker’s responsibility to resolve the functions, rather than loading them at run time, as the following example shows:
[DllImport("__Internal")]private static extern intCountLettersInString([MarshalAs(UnmanagedType.LPWStr)]string str);
You can define this kind of function in 
NativeFunctions.cpp
as follows:
extern "C" __declspec(dllexport) int __stdcall CountLettersInString(wchar_t* str){    int length = 0;    while (*str++ != L'\0')        length++;    return length;}
Because the linker resolves the function call, any error made in the function declaration on the managed side (C# code that executes under managed run time) produces a linker error instead of a run-time error. This means, no dynamic loading can take place during run time, and the function is called directly from C#, which significantly decreases the performance overhead of a 
P/Invoke
call.
Unity compiles source code plug-ins with the same C++ compiler arguments as the generated C++ code, which can't be modified. If some plug-in source code requires control over C++ compiler arguments, you must build a native plug-in instead. For more information, see Native plug-in.

IL2CPP build files

A project using the IL2CPP scripting backend typically produces these files:

IL2CPP files produced during build

The following files are common to projects that use IL2CPP:

File:

Description:

a_DataFolder with game data.
a.exeMain game executable.
UnityCrashHandler64.exeCrash handler executable.
UnityPlayer.dllUnity Player library containing all native code.
WinPixEventRuntime.dllPIX for Windows runtime. This file is present only in development builds.
a_BackUpThisFolder_ButDontShipItWithYourGameFolder containing data required to debug your game, including PDB (debug info) files and C++ code generated from your scripts. You should back up this folder for every build you ship, but don’t redistribute it.
GameAssembly.dllLibrary that contains the IL2CPP runtime and all your script code.
SymbolMapFile containing a list of all managed function addresses and their lengths. IL2CPP needs this to resolve managed stack traces. If you delete it, you can still run your game but there's no gurantee that exceptions will generate sensible call stacks.

Additional resources: