Unityネイティブプラグイン文字列やり取りの失敗例

BridgeCSharpToObjC.cs

using UnityEngine;
using System.Runtime.InteropServices;

public class BridgeCSharpToObjC : MonoBehaviour
{
	#if !UNITY_EDITOR
	[DllImport("__Internal")]
	static extern string Test_ ();
	#endif

	public static string Test ()
	{
		#if !UNITY_EDITOR
		return Test_ ();
		#endif
		return "";
	}

	void Update ()
	{
		Debug.Log (BridgeCSharpToObjC.Test ());
	}
}

TestPlugin.mm

#import <Foundation/Foundation.h>

extern "C"
{
    const char* Test_()
    {
        NSString *sample = @"Fugafuga";
        const char *str = [sample UTF8String];
        return str;
    }
}