Checking if a Pointer is valid .

[Jaafar Tribak]

Hi all .

Strictly speaking, this is not necessarly an excel related question but I thought I would post it here anyway as this forum has many bright members .... (I have already posted this question on a few VB forums but found no solution.)

I need to know the contents of a variable before passing it to the CopyMemory API in order to prevent the application from crashing.

* - To illustrate the problem, here is the first example that works because the lPtr variable correctly points to the Application Object.

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
pDest As Any, pSrc As Any, ByVal ByteLen As Long)

Sub Test()

    Dim lPtr As Long
    Dim oTempObject As Object

    lPtr = objPtr(Application)
    CopyMemory oTempObject, lPtr, 4
        MsgBox oTempObject.Name
    CopyMemory oTempObject, 0&, 4

End Sub

* - Here is the 2nd example that shows how passing a invalid Pointer in the lPtr variable ( in this case I have randomly chosen the number 1111 ) to the CoyMemory API causes a GPF and crashes the application.

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
pDest As Any, pSrc As Any, ByVal ByteLen As Long)

Sub Test()

    Dim lPtr As Long
    Dim oTempObject As Object

    lPtr = 1111 '<------ invalid Pointer.
    CopyMemory oTempObject, lPtr, 4 ' <--------- CRASH HERE !!!!!
        MsgBox oTempObject.Name
    CopyMemory oTempObject, 0&, 4

End Sub

In order to avoid this problem , I have tried using the following APIs : IsBadReadPtr ;IsBadWritePtr and IsBadCodePtr but without any luck so far.

Any help/thoughts much appreciated.