C++ delete crashes on certain instances

I have the following C++ method:

void MyClass::FindBottom ( CIppImage& bwImage, FieldRec* obField, int& bottomBorder_top, int& bottomBorder_bottom, int& topBorder_top, int& topBorder_bottom, bool& algoFoundBorder ){

    int scanYStart = topBorder_top + obField->getH() - VERTICAL_SCAN_AMOUNT;
    int scanYEnd = topBorder_top + obField->getH() + ( VERTICAL_SCAN_AMOUNT * 1.5 );
    int scanAmount = scanYEnd - scanYStart;
    int xScanEnd = obField->getOX() + obField->getW();

    int* histogram = new int[ scanAmount ];
    memset ( histogram, 0, (scanAmount) * sizeof(int) );

    Ipp8u* bwDataPtr = bwImage.DataPtr();

    int bwLineWidth = ( bwImage.Width() + 7 ) / 8;
    int n = 0;

    for( int y = scanYStart; y <= scanYEnd; y++ ){
        for( int x = obField->getOX(); x < xScanEnd; x++ ){
            if( ( GETBYTE( bwDataPtr, x, y, bwLineWidth ) ) != 0 && ( GETPIXEL(bwDataPtr, x, y, bwLineWidth ) ) != 0 ){
                histogram [ n ]++;
            }
        }
        n++;
    }

    int numFillPixelsThreshold = (int)(HORIZ_FILL_THRESHOLD * obField->getW());
    vector<int> goodRows;
    for( int j = 0; j < VERTICAL_SCAN_AMOUNT+VERTICAL_SCAN_AMOUNT+1; j ++ ){
        if( histogram[ j ] >= numFillPixelsThreshold ) {
            goodRows.push_back( scanYStart + j );
        }
    }
    if( goodRows.size() > 0 ){
        bottomBorder_top = goodRows[0];
     bottomBorder_bottom = goodRows[goodRows.size()-1];
    algoFoundBorder = true;
    }else{
        bottomBorder_top    = obField->getOY() + obField->getH() - 4;
        bottomBorder_bottom = obField->getOY() + obField->getH() + 4;
        algoFoundBorder = false;
    }
    delete[] histogram;
    histogram = 0;
}

There is 1 particular instance where the delete[] call crashes the program, Visual Studio returns the error message:

HEAP CORRUPTION DETECTED: after Normal block (#44325) at 0x01214980 CRT detected that the application wrote to memory after end of heap buffer.

Any ideas?

---

int scanAmount = scanYEnd - scanYStart; 
int n = 0; 
for( int y = scanYStart; y <= scanYEnd; y++ ){
   n++;
}
ASSERT(n == scanAmount); // failed, because your for loop makes one more step and as a result you corrupt heap

---

The size of the array is scanYEnd - scanYStart .

Your loop covers the inclusive range [scanYStart, scanYEnd] , the size of which is one larger than the array, so you write beyond the allocated memory. You will need to make the array one element larger.

(Off topic, but I would also suggest using std::vector rather than a manually allocated array, to fix the memory leak when an exception is thrown from this function. You could then use push_back inside the loop, to avoid having to calculate the size.)

---

There is at least one problem in this code. Let's suppose scanYStart is 0 and scanYEnd is 10. The size of the histogram array is 10 (10-0). And in the loop for( int y = scanYStart; y <= scanYEnd; y++ ){ iterates from 0 to 10 (including 10), ie 11 iterations. There is a heap corruption in the histogram [ n ]++; line then n is 10.

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