Access memory region that has already been displaced

Question

I am in the final process of developing a program and I came across an error, I already spent some time researching and I could not solve the problem.

About the program:

In summary, the program receives and writes values in another program (Aspen HYSYS) and communicates with OPC servers writing and receiving values.

Some details to clarify more:

To update the values in the main form, I created 3 threads, one takes the values from the server and writes to the program, one takes the values from the program and writes to the server and the other has the first principle, as a secondary thread cannot change anything in the form interface, each thread makes an invoke calling a delegate to update the values in the program.

To communicate with OPC servers, I use two Softing DLL’s.

My problem:

When I give the command to update the values, the following error appears: "Attempt to read or write protected memory. This is often an idication that other memory is Corrupt.". From what I’ve researched, it’s like I’m trying to write in a memory space that’s already been displaced. Explicitly, I haven’t dislocated anything, but some Softing method may have misplaced or deleted the reference without me knowing.

The error does not happen on a specific line, it varies between read and write methods on the server.

Code snippet where the error happens:

if (opcform.plcopc.URL == null)
{
   opcform.plcopc.URL =     opcform.plcopc.getURL(opcform.GridExport.Rows[i].Cells[6].Value.ToString(),opcform.GridExport.Rows[i]Cells[7].Value.ToString());
//o método acima apenas pega a URL do servidor
   opcform.plcopc.m_daSession = new DaSession(opcform.plcopc.URL);<<<<<<<<<<<<
//instancia uma sessão no servidor com a URL do mesmo
   opcform.plcopc.m_daSubscription = new DaSubscription(500, opcform.plcopc.m_daSession); <<<<<<<<<
//instancia um objeto necessário para fazer as leituras e escritas de forma síncrona e adiciona ele a sessão
}

opcform.plcopc.m_daItem = new DaItem(opcform.GridExport.Rows[i].Cells[8].Value.ToString(), opcform.plcopc.m_daSubscription); <<<<<<<<<<<

opcform.plcopc.exOptions.ExecutionType = EnumExecutionType.SYNCHRONOUS;
//seta que a comunicação vai ser síncrona
if (opcform.plcopc.m_daSession.CurrentState != EnumObjectState.CONNECTED)
{
    opcform.plcopc.m_daSession.Connect(true, true, opcform.plcopc.exOptions);
//conecta com o servidor
}
int retorno;
double vl = Convert.ToDouble(opcform.GridExport.Rows[i].Cells[4].Value);
//pega o valor que vai ser escrito no servidor
ValueQT vt = new ValueQT(vl, EnumQuality.GOOD, DateTime.Now);
//o objeto que vai ser escrito no servidor
opcform.plcopc.m_daItem.Write(vt, out retorno, opcform.plcopc.exOptions);<<<<<<
//escrevendo o objeto no servidor

Attempts:

Well, as they are in many lines the problem, I could not think of much, I tried to give a "lock" on some objects, but other errors appeared.

My request

Well, can someone tell me if there’s a way I can "block" the reference so only I can erase it? or how I can monitor to know where it is erased?

Please answer theoretically, you don’t need to enter thousands of lines of code and end up wasting your time. Materials so I can seek solution will be very welcome.

Answer 1

Yan, as he had suggested in the comments above, some people in the OS found a similar problem and suggested that it was an external problem. I don’t know if this will help you but here are some things I found in these links:

• This response in the OS here suggested that the error was on an Nvidea graphics card, which ended up generating the problem (wow!!!!!!!!!):

  https://stackoverflow.com/questions/4074585/attempted-to-read-or-write-protected-memory-this-is-often-an-indication-that-ot

• This other, although it is commercial software, identified that some servers on which its application is installed are on MediumTrust, and to solve the problem put in FullTrust:

http://manual.aspdotnetstorefront.com/p-1239-attempted-to-read-or-write-protected-memory.aspx

I don’t really know if it helps, but it’s worth looking into. Especially the first link, the developer takes the step by step how he got to the root of the problem using Windbg (http://msdn.microsoft.com/en-us/library/windows/hardware/ff551063%28v=vs.85%29.aspx).