Crash when opening web page http://build.webkit.org/waterfall.

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 355 matching lines @@
     }
 
     ASSERT(!remainder);
 
     extraRowSpanningHeight -= accumulatedPositionIncrease;
 }
 
 // To avoid unneeded extra height distributions, we apply the following sorting algorithm:
 // 1. We sort by increasing start row but decreasing last row (ie the top-most, shortest cells first).
 // 2. For cells spanning the same rows, we sort by intrinsic size.
 static bool compareRowSpanCellsInHeightDistributionOrder(const RenderTableCell* cell2, const RenderTableCell* cell1)

[Julien - ping for review, 2013/08/22 21:48:08]

I missed that at the previous review. The arguments are named *backwards*. That
makes the code nearly-impossible to get right.

I couldn't actually review the correctness as it's too crazy for me to parse.

[suchit.agrawal, 2013/08/23 13:37:26]

Done.

 {
     unsigned cellRowIndex1 = cell1->rowIndex();
     unsigned cellRowSpan1 = cell1->rowSpan();
     unsigned cellRowIndex2 = cell2->rowIndex();
     unsigned cellRowSpan2 = cell2->rowSpan();
 
     if (cellRowIndex1 == cellRowIndex2 && cellRowSpan1 == cellRowSpan2)
         return (cell2->logicalHeightForRowSizing() > cell1->logicalHeightForRowSizing());
+    else if (cellRowIndex2 >= cellRowIndex1 && (cellRowIndex2 + cellRowSpan2) <= (cellRowIndex1 + cellRowSpan1))

[Julien - ping for review, 2013/08/22 21:48:08]

The else is not mandated as you return all the time.

I would advocate towards commenting this code (with why comments) as it is
getting really hairy.

[suchit.agrawal, 2013/08/23 13:37:26]

Done.

+        return true;
+    else if (!(cellRowIndex1 >= cellRowIndex2 && (cellRowIndex1 + cellRowSpan1) <= (cellRowIndex2 + cellRowSpan2)))
+        return (cellRowIndex2 < cellRowIndex1);
 
-    return (cellRowIndex2 >= cellRowIndex1 && (cellRowIndex2 + cellRowSpan2) <= (cellRowIndex1 + cellRowSpan1));
+    return false;

[a.suchit, 2013/08/22 10:26:17]

I think now it is strict equality. We are sorting the cells based on their row
indexes but if 2 cells are same size then more height cell will come first and
if one cell inside another cell then inner cell will come first.

[Julien - ping for review, 2013/08/22 21:48:08]

I don't have your confidence and based on the fact that we got it wrong once
already, I am betting that there are other bugs lying in the code.

[suchit.agrawal, 2013/08/23 13:37:26]

Sorry but last time, I don't have whole idea about std::sort(), how does it work
so I did mistake.

 }
 
 // Distribute rowSpan cell height in rows those comes in rowSpan cell based on the ratio of row's height if
 // 1. RowSpan cell height is greater then the total height of rows in rowSpan cell
 void RenderTableSection::distributeRowSpanHeightToRows(SpanningRenderTableCells& rowSpanCells)
 {
     ASSERT(rowSpanCells.size());
 
     // 'rowSpanCells' list is already sorted based on the cells rowIndex in ascending order
     // Arrange row spanning cell in the order in which we need to process first.
@@ skipping 1287 matching lines @@
     if (!style()->isLeftToRightDirection())
         cellLocation.setX(table()->columnPositions()[table()->numEffCols()] - table()->columnPositions()[table()->colToEffCol(cell->col() + cell->colSpan())] + horizontalBorderSpacing);
     else
         cellLocation.setX(table()->columnPositions()[effectiveColumn] + horizontalBorderSpacing);
 
     cell->setLogicalLocation(cellLocation);
     view()->addLayoutDelta(oldCellLocation - cell->location());
 }
 
 } // namespace WebCore