Windows Player: IL2CPP Scripting Backend

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 IL2CPPA Unity-developed scripting back-end which you can use as an alternative to Mono when building projects for some platforms. More info
See in Glossary 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:

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 int
CountLettersInString([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-inA platform-specific native code library that is created outside of Unity for use in Unity. Allows you can access features like OS calls and third-party code libraries that would otherwise not be available to Unity. More info
See in Glossary.

IL2CPP build files

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

The following files are common to projects that use IL2CPP:

Additional resources:

• Plugin Inspector
• IL2CPP
• Use P/Invoke