[ERROR: Access violation writing at location] while using IRowsetfastload

This is a discussion on [ERROR: Access violation writing at location] while using IRowsetfastload within the C++ Programming forums, part of the General Programming Boards category; ------------------------------------------------------------------------------------ Code: pData = (BYTE *)malloc(ulOffset + 300); for (iRow = 0 ; iRow < nSz ; iRow++) { // ...

  1. #1
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    Join Date
    Aug 2008
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    1

    [ERROR: Access violation writing at location] while using IRowsetfastload

    ------------------------------------------------------------------------------------
    Code:
     pData = (BYTE *)malloc(ulOffset + 300);
    
       for (iRow = 0 ; iRow < nSz ; iRow++)
       {
    	   // Column: 1
    	   *(DBSTATUS *)(pData + rgBinding[0].obStatus) = DBSTATUS_S_OK;
    	   *(DBLENGTH *)(pData + rgBinding[0].obLength) = 1234567;   // Ignored for I4 data
    	   *(LONG *)(pData /*+ rgBinding[0].obValue*/) = nSessionId;
    
    	   // Column: 2
    	   *(DBSTATUS *)(pData + rgBinding[1].obStatus) = DBSTATUS_S_OK;
    	   *(DBLENGTH *)(pData + rgBinding[1].obLength) = 1234567;   // Ignored for I4 data
    	   *(LONG *)(pData + rgBinding[1].obValue) = nDataID;
    	   
    	   // Column: 3
    	   *(DBSTATUS *)(pData + rgBinding[2].obStatus) = DBSTATUS_S_OK;
    	   *(DBLENGTH *)(pData + rgBinding[2].obLength) = 1234567;   // Ignored for I4 data
    	   *(LONG *)(pData + rgBinding[2].obValue) = iRow;
    
    	   _bstr_t strVal = TableValues[iRow];
    	   VARIANT * Coldata = new VARIANT;
    	   Coldata->vt = VT_BSTR;
    	   Coldata->bstrVal = strVal;
    
    	   VARIANT * temp = new VARIANT;
    	   temp->vt = VT_INT;
    	   temp->fltVal= 10;	
    
    	   // Column: 4
    	   strVal = "01/01/04";
    	   temp->vt = VT_BSTR;
    	   temp->bstrVal = strVal;
    	   
    	   *(DBSTATUS *)(pData + rgBinding[3].obStatus) = DBSTATUS_S_OK;
    	   *(DBLENGTH *)(pData + rgBinding[3].obLength) = 1234567;   // Ignored for I4 data
    	   *(VARIANT *)(pData + rgBinding[3].obValue) = *temp;
    
    	   // Column: 5
    	   *(DBSTATUS *)(pData + rgBinding[4].obStatus) = DBSTATUS_S_OK;
    	   *(DBLENGTH *)(pData + rgBinding[4].obLength) = 1234567;   // Ignored for I4 data
    	   *(VARIANT *)(pData + rgBinding[4].obValue) = *Coldata;
    
    	   // Column: 6
    	   *(DBSTATUS *)(pData + rgBinding[5].obStatus) = DBSTATUS_S_OK;
    	   *(DBLENGTH *)(pData + rgBinding[5].obLength) = 1234567;   // Ignored for I4 data
    	   *(VARIANT *)(pData + rgBinding[5].obValue) = *temp;
    
    	   // Column: 7
    	   *(DBSTATUS *)(pData + rgBinding[6].obStatus) = DBSTATUS_S_OK;
    	   *(DBLENGTH *)(pData + rgBinding[6].obLength) = 1234567;   // Ignored for I4 data
    	   *(VARIANT *)(pData + rgBinding[6].obValue) = *temp;
    
    	   // Column: 8
    	   *(DBSTATUS *)(pData + rgBinding[7].obStatus) = DBSTATUS_S_OK;
    	   *(DBLENGTH *)(pData + rgBinding[7].obLength) = 1234567;   // Ignored for I4 data
    	   *(LONG *)(pData + rgBinding[7].obValue) = 1;
    
    	   assert (pData);
    	
    	   if (SUCCEEDED(hr))
    		   hr = pIRowsetFastLoad->InsertRow(hAcc, pData);
    <THIS IS WHERE ACCESS VIOLATION OCCURS>

    ------------------------------------------------------------------------------------

    Here are debug values for pData:


    Code:
    		
                    *(LONG *)(pData )	= 280	long
    
    		*(LONG*)(pData + 28)	= 4	long
    
    		*(LONG*)(pData + 64)	 = 0	long
    
    		*(VARIANT*)(pData + 100)	BSTR = 0x00000000001c1b78 "01/01/04"	tagVARIANT
    
    		*(VARIANT*)(pData + 136)	BSTR = 0x00000000001bf5d8 "0"	tagVARIANT
    
    		*(VARIANT*)(pData + 172)	BSTR = 0x00000000001c1b78 "01/01/04"	tagVARIANT
    
    +		*(VARIANT*)(pData + 208)	BSTR = 0x00000000001c1b78 "01/01/04"	tagVARIANT
    
    		*(LONG*)(pData + 244)	= 1	long

    As you can see, I've already hacked up my code to find out whats causing this exception.. Any help would be very appreciated!
    Last edited by krCode; 08-13-2008 at 12:05 AM.

  2. #2
    Kernel hacker
    Join Date
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    Location
    Farncombe, Surrey, England
    Posts
    15,677
    That code is HORRIBLE. Far too much casting going for anyone with less than planetary sized brain to follow what is going on - I'm sure the problem can be solved in a neater way.

    Also: assert (pData);
    is WAY too late - you have just accessed memory through pData 8 * 3 times, so if it was NULL, the program would have crashed a long time ago.

    Code:
    *(LONG *)(pData /*+ rgBinding[0].obValue*/) = nSessionId;
    Is that commented out bit [in red] becuase you know that it's always zero, so therefore can be eliminated. Don't you think the compiler is better at figuring that out?

    Finally, on the line where it crashes:
    Code:
     hr = pIRowsetFastLoad->InsertRow(hAcc, pData);
    What is pIRowsetFastLoad, what is hAcc? What does InsertRow do?

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

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