Trouble with C#<->C++ DLLImport "Attempted to read or write protected memory."

I have a C++ dll which has a function within it I am trying to call from a C# application.

Here's the code in the C++ header file

extern "C" _declspec(dllexport) int LabelStoringSSDsim(int devNum, UCHAR serial[40], UCHAR wwn[40],
                UCHAR ConfigID[5], UCHAR FrmRev[8], UCHAR DevName[40], int eCode);

Here's the code in the C++ source file

int LabelStoringSSDsim(int devNum, UCHAR serialLbl[40], UCHAR wwnLbl[40],
                UCHAR ConfigID[5], UCHAR FrmRev[8], UCHAR DevName[40], int eCode)
{

    string strConfigID="12111";                                     //5 bytes
    string strFrmRev="1.25....";                                    //8 bytes
    string strDevName="ABC-123.................................";   //40 bytes

    for (int i=0;i<5;i++)
        ConfigID[i] = strConfigID[i];

    for (int i=0;i<8;i++)
        FrmRev[i] = strFrmRev[i];

    for (int i=0;i<40;i++)
        DevName[i] = strDevName[i];
    return eCode;
}

Here's the C# relevant code

[DllImport("LabelStoring.dll")]
static extern int LabelStoringSSDsim(
    int devNum,
    byte[] strserial,
    byte[] strwwn,
    [In] ref byte[] ConfigID,
    [In] ref byte[] FrmRev,
    [In] ref byte[] DevName,
    int eCode
);


int errNum = LabelStoringSSDsim(devNum, bserial, bwwn, ref ConfigID, ref FrmRev, ref DevName, 123123);

So when I get to the last bit of code there I get the "Attempted to read or write protected memory. This is often an indication that other memory is corrupt." error.

I have no prior experience in importing DLL's like this and I've done a lot of searching but cannot seem to find a solution to the problem.

I tried starting over from scratch with a simple function returning an integer, and that worked. Then I added an int for me to pass to the function and it still worked. Then I added a byte array for me to pass, which worked. Then I atte

c# c++ reference dllimport

Edit Report

I started getting this exception durring native interop periodically after upgrading to Windows 7. The code had always worked on XP and has fewer issues on Win 7 if I ran my app in XP compatibility mode.

After some research and experimentation I discovered that the reason I was getting this exception had to do with calling a native function that returned a string (WCHAR*).

I don’t believe there is currently a fix for this as even updating to .Net 3.5 didn’t fix the issue… However I did find the following work around.

Example of what works on XP but doesn’t work on Win 7:

[DllImport("NativeBin.dll")]
public static extern String GetWCharStr();

Example of what works for me on Win 7 and XP:

[DllImport("NativeBin.dll")]
private static extern IntPtr GetWCharStr();
public static String GetString()
{
    return Marshal.PtrToStringUni(GetWCharStr());
}

answered 2011-05-05T20:48:52.093

Trouble with C#<->C++ DLLImport "Attempted to read or write protected memory."

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