c++ com interop use c# dll memory leak

Question

Hello,

I have a Problem with my c++ program that uses a c# dll as com- object. It seems to have a Memory leak. The used Memory increases slowly. Can anybody help me? How can I solve the Problem?

I have attached a code snipped of the c# code and of the c++ dll that uses the c# dll.

Thanks,

Ralf

c++ code:


#import "C:\temp\test_con.tlb" named_guids

bool TestCommunicator::Connect ()
{

    long count = 0;
    unsigned char* data = NULL;

    HRESULT hr;
    hr = CoInitialize(NULL);

    p.CreateInstance(__uuidof(TestCon_Con::Test_Con));


    if (p->Connect())
    {
        while ( m_stop == false )
        {
            p->ReadPDOData3 (&count, &data);   // <-- when this function is called the Memory is slowly increasing
         }

        p->DisConnect();
        p.Release();
    }

    CoUninitialize();
}


c# code:

using Syst
em;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;


namespace TestCon_Con
{
    [Guid("C751C166-2094-4F1F-A47D-9556991F460B")]
    public interface TestInterface
    {
        [DispId(1)]
        bool Connect();

        [DispId(2)]
        bool DisConnect();

        [DispId(3)]
        byte[] GetBusData();

        [DispId(4)]
        void ReadPDOData3([In, Out] ref int nNumElements,
                          [In, Out, MarshalAs(UnmanagedType.LPArray, SizeParamIndex=0)] ref byte [] bArray );

    }


    [Guid("47361D08-F31D-416A-B599-97F473ACC276"),
    InterfaceType(ComInterfaceType.InterfaceIsIDispatc  h)]
    public interface Test_Events
    {
    }

    [Guid("7A0E9679-FD21-486D-BAE7-9387F0C2B9F1"),
    ClassInterface(ClassInterfaceType.None),
    ComSourceInterfaces(typeof(Test_Events))]
    public class Test_Con : TestInterface
    {


        public bool Connect()
        {
            return true;
        }


        public bool DisConnect()
        {
            return true;
        }


        public byte[] GetBusData()
        {
            return null;
        }


        public void ReadPDOData3(ref int count, ref byte[] data)
        {
            data = new byte [15];
            for (int i = 0; i < 15; i++)
            {
            data[i] = i;
            }
            count = data.Length;
        }
    }
}

Answer 1

Hallo,

da Du in einem deutschen Forum gefragt hast, die Antwort in deutsch:

Das automatische Speichermanagement durch den GC gilt nur für .NET. Sobald Du einen Interop-Aufruf verwendest, COM oder nicht, musst Du den Speicher über CoTaskMemFree freigeben.

Die gilt nicht nur für Arrays, die in .NET anders verwaltet werden, als in unmanaged Code.

Siehe dazu: Memory Management with the Interop Marshaler

und Default Marshaling for Arrays

Gruß Elmar