ASSERTION FAILED: !remainder in WebCore::RenderTableSection::distributeExtraRowSpanHeightToAutoRows

Source/core/rendering/RenderTableSection.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 310 matching lines @@
                 toAdd = min(toAdd, extraRowSpanningHeight);
                 accumulatedPositionIncrease += toAdd;
                 extraRowSpanningHeight -= toAdd;
                 percent -= m_grid[row].logicalHeight.percent();
             }
         }
         m_rowPos[row + 1] += accumulatedPositionIncrease;
     }
 }
 
+// Some time multiplication of below 2 values is overflowing from integer. So
+// type of variable in computation are taken as 'long long' in place of int.
+// In this computation, only 2 integer variables are multiplied which would not
+// overflow long long.
+static int calcIncreasedRowHeight(long long extraHeight, long long rowHeight, long long totalHeight, int& remainder)

[Julien - ping for review, 2014/03/10 18:36:39]

Let's not abbreviate function names.

I don't really like how we mix side effect with return value. I would rather
that the code pass |accumulatedPositionIncrease| and modify it and return
nothing.

[a.suchit, 2014/03/11 12:33:56]

Done.

+{
+    remainder += (extraHeight * rowHeight) % totalHeight;

[Julien - ping for review, 2014/03/10 18:36:39]

Per my comment, there should be some ASSERT about the types' sizes.

COMPILE_ASSERT(sizeof(long long int) > sizeof(int));

This ensures that we can't overflow in the multiplication and will catch
platform that breaks the new code's assumption.

[a.suchit, 2014/03/11 12:33:56]

Done.

+    return (extraHeight * rowHeight) / totalHeight;
+}
+
 void RenderTableSection::distributeExtraRowSpanHeightToAutoRows(RenderTableCell* cell, int totalAutoRowsHeight, int& extraRowSpanningHeight, Vector<int>& rowsHeight)
 {
     if (!extraRowSpanningHeight || !totalAutoRowsHeight)
         return;
 
     const unsigned rowSpan = cell->rowSpan();
     const unsigned rowIndex = cell->rowIndex();
     int accumulatedPositionIncrease = 0;
     int remainder = 0;
 
     // Aspect ratios of auto rows should not change otherwise table may look different than user expected.
     // So extra height distributed in auto spanning rows based on their weight in spanning cell.
     for (unsigned row = rowIndex; row < (rowIndex + rowSpan); row++) {
         if (m_grid[row].logicalHeight.isAuto()) {
-            accumulatedPositionIncrease += (extraRowSpanningHeight * rowsHeight[row - rowIndex]) / totalAutoRowsHeight;
-            remainder += (extraRowSpanningHeight * rowsHeight[row - rowIndex]) % totalAutoRowsHeight;
+            accumulatedPositionIncrease += calcIncreasedRowHeight(extraRowSpanningHeight, rowsHeight[row - rowIndex], totalAutoRowsHeight, remainder);
 
             // While whole extra spanning height is distributing in auto spanning rows, rational parts remains
             // in every integer division. So accumulating all remainder part in integer division and when total remainder
             // is equvalent to divisor then 1 unit increased in row position.
             // Note that this algorithm is biased towards adding more space towards the lower rows.
             if (remainder >= totalAutoRowsHeight) {
                 remainder -= totalAutoRowsHeight;
                 accumulatedPositionIncrease++;
             }
         }
@@ skipping 12 matching lines @@
 
     const unsigned rowSpan = cell->rowSpan();
     const unsigned rowIndex = cell->rowIndex();
     int accumulatedPositionIncrease = 0;
     int remainder = 0;
 
     // Aspect ratios of the rows should not change otherwise table may look different than user expected.
     // So extra height distribution in remaining spanning rows based on their weight in spanning cell.
     for (unsigned row = rowIndex; row < (rowIndex + rowSpan); row++) {
         if (!m_grid[row].logicalHeight.isPercent()) {
-            accumulatedPositionIncrease += (extraRowSpanningHeight * rowsHeight[row - rowIndex]) / totalRemainingRowsHeight;
-            remainder += (extraRowSpanningHeight * rowsHeight[row - rowIndex]) % totalRemainingRowsHeight;
+            accumulatedPositionIncrease += calcIncreasedRowHeight(extraRowSpanningHeight, rowsHeight[row - rowIndex], totalRemainingRowsHeight, remainder);
 
             // While whole extra spanning height is distributing in remaining spanning rows, rational parts remains
             // in every integer division. So accumulating all remainder part in integer division and when total remainder
             // is equvalent to divisor then 1 unit increased in row position.
             // Note that this algorithm is biased towards adding more space towards the lower rows.
             if (remainder >= totalRemainingRowsHeight) {
                 remainder -= totalRemainingRowsHeight;
                 accumulatedPositionIncrease++;
             }
         }
@@ skipping 1336 matching lines @@
     else
         cellLocation.setX(table()->columnPositions()[effectiveColumn] + horizontalBorderSpacing);
 
     cell->setLogicalLocation(cellLocation);
 
     if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled())
         view()->addLayoutDelta(oldCellLocation - cell->location());
 }
 
 } // namespace WebCore