Unity でネイティブ側から Debug.Log() するヤツ

debug_log.cpp

#if defined(__CYGWIN32__)
    #define UNITY_INTERFACE_API __stdcall
    #define UNITY_INTERFACE_EXPORT __declspec(dllexport)
#elif defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || defined(_WIN64) || defined(WINAPI_FAMILY)
    #define UNITY_INTERFACE_API __stdcall
    #define UNITY_INTERFACE_EXPORT __declspec(dllexport)
#elif defined(__MACH__) || defined(__ANDROID__) || defined(__linux__) || defined(__QNX__)
    #define UNITY_INTERFACE_API
    #define UNITY_INTERFACE_EXPORT
#else
    #define UNITY_INTERFACE_API
    #define UNITY_INTERFACE_EXPORT
#endif


extern "C"
{
    using debug_log_func_type = void(UNITY_INTERFACE_API *)(const char*);
    
    namespace
    {
        debug_log_func_type debug_log_func = nullptr;
    }
    
    void debug_log(const char* msg)
    {
        if (debug_log_func != nullptr) debug_log_func(msg);
    }
    
    UNITY_INTERFACE_EXPORT void set_debug_log_func(debug_log_func_type func)
    {
        debug_log_func = func;
    }
    
    UNITY_INTERFACE_EXPORT void debug_log_test()
    {
        debug_log("hogehoge");
    }
}

DebugLogTest.cs

using UnityEngine;
using System;
using System.Runtime.InteropServices;

public class NativeDebugLog : MonoBehaviour 
{
  public delegate void DebugLogDelegate(string str);
	DebugLogDelegate debugLogFunc = msg => Debug.Log(msg);

	[DllImport ("unity_debug_log")]
	public static extern void set_debug_log_func(DebugLogDelegate func);
	[DllImport ("unity_debug_log")]
	public static extern void debug_log_test();

	void Start() 
	{
		debug_log_test();
		set_debug_log_func(debugLogFunc);
		debug_log_test();
	}
}