CopyMemory: Memory Access Violation

[colin glenn]

The whole error message:

Exception: Memory Access Violation
Program tried to read or write an invalid memory address

The code that causes it:

PROPERTY SET MemoryBuffer(BYVAL dwLength AS DWORD, BYVAL dwData AS DWORD)
' note that depending on what you're passing
' length needs to be ZERO based
    LOCAL pBuffer, pSource AS BYTE POINTER, pLength, pIndex AS DWORD
    REDIM memBuffer(dwLength)
    pSource = dwData
    pBuffer = VARPTR(memBuffer(0))
    pLength = dwLength ' + 1
    CopyMemory(pBuffer,pSource,pLength)
END PROPERTY

dwData is a pointer to STRPTR(dynamicstring$)
dwLength is the length of the string -1

If I replace the CopyMemory with this:

    FOR pIndex = 0 TO dwLength
        memBuffer(pIndex) = @pSource[pIndex]
    NEXT pIndex

It works, so it must be something in the way I'm passing the pointers to CopyMemory that's wrong.

Anyone out there can Clue/4 me?

[Kev Peel]

Use BYVAL on parameters 1 and 2. CopyMemory is simply an encapsulation of the MoveMemory API function (ie. they are exactly the same)

[colin glenn]

Well, that worked, now to work around another issue, and that is, you can't pass FreeImage_GetFileTypeFromHandle a reference to an Object and expect the object to pass through unscathed, apparently FreeImage is calling the Object's DESTROY mechanism somewhere.

[Chris Holbrook]

Well, that worked, now to work around another issue

Colin, you would probably get more exposure if you post the new issue in a seperate thread. Also, as FreeImage is a bit of a minority interest, it might be worth posting the function prototype and the code which you are using. HTH.