EntryPointNotFoundException With Unity Plugin - c++

Question

I'm very new to writing c++ plugins for unity but must do so now. I have been loosely following this tutorial and created the following in a visual studio dll project uncreatively called UnityPluginTest:
#include <stdint.h>
#include <stdlib.h>
#include <time.h>
#define DLLExport __declspec (dllexport)
extern "C"
{
DLLExport int RandomNumber(int min, int max)
{
srand((unsigned int)time(0));
return (rand() % (max - min) + min);
}
}
I created a completely new unity project to test it (Unity 2020.2.f1 if it matters), and copied the compiled .dll file into a new folder Assets/Plugins. I then made a new script called (equally uncreatively) TestFirstUnityPluginTest.cs which contains the following:
using System.Runtime.InteropServices;
using UnityEngine;
public class TestFirstUnityPluginTest : MonoBehaviour
{
const string dll = "__Internal";
[DllImport(dll)]
private static extern int RandomNumber(int min, int max);
void Start()
{
Debug.Log(RandomNumber(0, 10));
}
}
When I put the script on a gameobject and hit play, I get an error stating "EntryPointNotFoundException: RandomNumber" with a stack trace pointing to the Debug.Log() call. Any ideas what I might be doing wrong? Thank you in advance.

Answer 1

You should specify entry point and use DECORATED name:
replace [DllImport(dll)] by [DllImport("YOUR_DLL_NAME.dll", EntryPoint = "DecoratedFunctionName")]
My C++ code:
__declspec(dllexport) int Double(int number)
{
return number * 2;
}
My Unity3d C# code:
[DllImport("Dll4_CPP.dll", EntryPoint = "?Double##YAHH#Z")]
public static extern int Double(int number);
void Start()
{
Debug.Log(Double(10));
}
Decorated name - name of the function inside DLL (compiler renames it).
Dumpbin.exe helps to find it:
VisualStudion2019 -> Tools -> CommandLine -> DeveloperComandPrompt
cd <your PathToDLL>
dumpbin /exports Dll4_CPP.dll
it will print:
...
1 0 00011217 ?Double##YAHH#Z = #ILT+530(?Double##YAHH#Z)
...
Source