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

Source/core/rendering/RenderTableSection.cpp

Index: Source/core/rendering/RenderTableSection.cpp
diff --git a/Source/core/rendering/RenderTableSection.cpp b/Source/core/rendering/RenderTableSection.cpp
index d0e9ba961b9e24556333e02eb4e43e5edbe99931..6a8366e6d380c556c38279ff59934ca3e16e624d 100644
--- a/Source/core/rendering/RenderTableSection.cpp
+++ b/Source/core/rendering/RenderTableSection.cpp
@@ -328,6 +328,16 @@ void RenderTableSection::distributeExtraRowSpanHeightToPercentRows(RenderTableCe
     }
 }
 
+// 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)
@@ -342,8 +352,7 @@ void RenderTableSection::distributeExtraRowSpanHeightToAutoRows(RenderTableCell*
     // 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
@@ -376,8 +385,7 @@ void RenderTableSection::distributeExtraRowSpanHeightToRemainingRows(RenderTable
     // 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