Hallo Everybody,

I amtrying to use an old unmanaged dll in my VBE2008 Project. My applicationworks fine on mycomputers (3 Vista sp1 and 2 XP sp3 / all with .net framwork 3.5), but after the sp2 update for2 ofVista machines,it throws often (not every time) an AccessViolationException.The error message is:
"Attempt to read or write protected memory. This is often an indication that other memory is corrupt."

I have checked and found thattheexceptionwas thrown bythedll callingfunction.My code looks like this:

The dll is in the same directory with my app and I have tried with the absolute reference like "c:\abc.dll".
How can i fix it? any idea?

thx.

Lert Pianapitham

Hi Lert,

Commonly Access Violation is raised by following factors:

1. Reading/Writing invalid memory block.
2. Accessing memory that has not been allocated or has been freed already
3. Accessing memory address that is reserved (e.g. kernel use >0x7FFFFFFF)
4. Writing to memory block that is marked as “Read-Only�(immutable strings)
5. Wrapped as NullReferenceException/AccessViolationException in .Net


Could you give us native C++ function definition so that we can confirm that the managed signature is correct? Whether you can run this application in Windows7 or Windows2008 without problems (Because I haven't Vista SP2 computer, I want to know if this question occurs in Windows7 or Windows2008 so that I can reproduce your scenario if you can send me your C++ DLL). Commonly we need to use Debugger to investigate this question. Please have a look at this demo:
http://stackoverflow.com/questions/1331320/using-windbg-to-inspect-method-parameters-in-raw-memory-from-crash-dump

We can directly attach Windbg to break at the Exception to investigate the question.

---

Best regards,
Riquel
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Also ... with the Vista sp1 and XP sp2, itworks every time. Only 2 machineswith Vistasp2have this problem.

thx. again
Lert Pianapitham

Hi Lert,

Commonly Access Violation is raised by following factors:

1. Reading/Writing invalid memory block.
2. Accessing memory that has not been allocated or has been freed already
3. Accessing memory address that is reserved (e.g. kernel use >0x7FFFFFFF)
4. Writing to memory block that is marked as “Read-Only�(immutable strings)
5. Wrapped as NullReferenceException/AccessViolationException in .Net


Could you give us native C++ function definition so that we can confirm that the managed signature is correct? Whether you can run this application in Windows7 or Windows2008 without problems (Because I haven't Vista SP2 computer, I want to know if this question occurs in Windows7 or Windows2008 so that I can reproduce your scenario if you can send me your C++ DLL). Commonly we need to use Debugger to investigate this question. Please have a look at this demo:
http://stackoverflow.com/questions/1331320/using-windbg-to-inspect-method-parameters-in-raw-memory-from-crash-dump

We can directly attach Windbg to break at the Exception to investigate the question.

---

Best regards,
Riquel
Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.

Hi Riquel_Dong,

thank for your answer.

Sorry ... Icannot give you the dll due to the Program's licence.But i thinkyou can have one from internet if you want to do a search.It's name RefProp.dll.

My Investigation (with vbe debugger) told me that dll calling command is the error. I will try the DebugDiag today.

thanks again

Lert