c++ com interop use c# dll memory leak

[ralf01]

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?

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

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);
}

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

CoUninitialize();
}


c# code:

using System;
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;
}
}
}

[weaknessforcats]

You have this code:

unsigned char* data = NULL;
 

and this code:

while ( m_stop == false )
 {
 p->ReadPDOData3 (&count, &data);
etc...
 

and this code:

public void ReadPDOData3(ref int count, ref byte[] data)
 {
 data = new byte [15];
etc...

So I see data defined as an unsigned char* whose address is repeatedly passed to ReadPDOData3 where a heap allocation is made and the address of the allocation placed in data. But I never see where data is deleted before overstoring it. In fact I never see a delete on data at all. This looks like a 15 byte leak on every ReadPDOData3 call.

Using naked pointers like this is a big no-no in C++. Consider using a smart pointer instead.