Describes the use of plug-ins for macOS applications using Intermediate Language To C++ (IL2CPP).
IL2CPP is a fully supported scripting back end that you can use as an alternative to Mono when building projects for macOS Player.
When you use IL2CPP to build a project, Unity converts Intermediate Language (IL) code from scripts and assemblies to C++ before creating a native binary. Refer to IL2CPP for more information.
You can add C++ (.cpp) code files directly into a Unity Project when using the IL2CPP scripting back end. These C++ files act as plug-ins within the Inspector. If you configure the C++ files to be compatible with macOS Player, Unity compiles them together with C++ code that gets generated from managed assemblies. Refer to Import and configure plug-ins for more information on plug-in configuration.
Generated C++ code links the functions together, removing the need for a separate Dynamic Link Library (DLL). Instead of using the DLL name, use the "__Internal" keyword to make the C++ linker responsible for resolving functions rather than loading them at runtime. For example:
[DllImport("__Internal")]
private static extern int
CountLettersInString([MarshalAs(UnmanagedType.LPWStr)]string str);
可在 NativeFunctions.cpp 中定义此类函数，如下所示：
extern "C" __declspec(dllexport) int __stdcall CountLettersInString(wchar_t* str)
{
int length = 0;
while (*str++ != nullptr)
length++;
return length;
}
When the linker resolves the function call, errors in the function declaration on the managed side result in a linker error rather than a runtime error. This means that no dynamic loading needs to happen during runtime, with the function called directly from C#. This decreases the performance overhead of a P/Invoke call.