CODEWITHSUNDEEP
c#cdlldllimportaccess-violation
mmpatel009
mmpatel009

Reputation: 941

AccessViolationExceptiond: Attempted to read/write protected memory

I have a DLL file that is written in C. I am try to use in C DLL (ImportDLL) in my C# code. My method return out parameter. C method is called correctly but it crashed after process and gives error **"System.AccessViolationException: Attempted to read or write protected memory.

This is often an indication that other memory is corrupt"** after process completed.

My C declaration

int preProcessAndBestImagesC(
      char* ...,
      size_t* ...,
      char** ...,
      size_t* ...,
      (struct)* ...,
      size_t* ...,
      int** ...,
      (struct)** ...,
      int ...,
      int printStatus
    );

My C# Declaration

[DllImport(@"abc.dll", CallingConvention = CallingConvention.StdCall, SetLastError = true, BestFitMapping = true, EntryPoint = "xxx")]
    [return: MarshalAs(UnmanagedType.I4)]
    unsafe private static extern int xxx(
        String p_ ...,                                               
        [MarshalAs(UnmanagedType.I2)] out UInt16 p_numImageFilesOrDirs,

        String[] p_vecImageFilesOrDirs,             

        [MarshalAs(UnmanagedType.I2)] out UInt16 ...,
        [MarshalAs(UnmanagedType.LPArray)] out (struct)[] ...,
        [MarshalAs(UnmanagedType.I2)] out UInt16 ...,
        out Int16[] ...,
        [MarshalAs(UnmanagedType.LPArray)] out (struct)[] ...,
        [MarshalAs(UnmanagedType.I2)] Int16 ...,
        [MarshalAs(UnmanagedType.I2)] Int16 ...
    );

Does anyone know what the problem is?

Upvotes: 0

Views: 600

Answers (3)

Rahul Shukla
Rahul Shukla

Reputation: 1292

I would suggest the following:

Considering the DLL returns a POINTER to the memory, please make sure to Marshaling your data/parameter. You can use INTPTR to point to the memory allocated by DLL.

Also, make sure the DLL doesn't implicitly deletes the allocated memory. If it does, please consider re-writing the DLL code (if possible)

Hope this helps.

Upvotes: 0

Bernhard Hiller
Bernhard Hiller

Reputation: 2407

The declaration, e.g. marshalling of parameters, cdecl/stdcall, could be wrong.

It could also be a Data Execution Prevention (DEP) issue. In that case, use

editbin.exe /NXCOMPAT:NO "$(TargetPath)"

in the postbuild event.

Upvotes: 0

Abhishek
Abhishek

Reputation: 75

Without code it is hard to answer your question but you can use following steps as suggested by msdn

Go to

Tools->Options

Debugging->General

uncheck option "Suppress JIT optimization on module load"

Upvotes: 0

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