spread_footprints.cpp: try to avoid integer overflow when spreading footprints.

In rare cases (one known case) sizes of areas used as container when spreading
footprints can become negative, thus hanging pcbnew.
Happens if many footprints are very big (say 80cm).

Now if there is no room to place footprints, some are stacked.

pcbnew/autorouter/spread_footprints.cpp

@@ -108,6 +108,7 @@ void spreadRectangles( CRectPlacement& aPlacementArea,
 
     // Add all subrects
     CSubRectArray::iterator it;
+
     for( it = vecSubRects.begin(); it != vecSubRects.end(); )
     {
         CRectPlacement::TRect r( 0, 0, it->w, it->h );
@@ -116,12 +117,27 @@ void spreadRectangles( CRectPlacement& aPlacementArea,
 
         if( !bPlaced )   // No room to place the rectangle: enlarge area and retry
         {
-            areaSizeX = ceil(areaSizeX * 1.1);
+            bool retry = false;
-            areaSizeY = ceil(areaSizeY * 1.1);
+
+            if( areaSizeX < INT_MAX/2 )
+            {
+                retry = true;
+                areaSizeX = areaSizeX * 1.2;
+            }
+
+            if( areaSizeX < INT_MAX/2 )
+            {
+                retry = true;
+                areaSizeY = areaSizeY * 1.2;
+            }
+
+            if( retry )
+            {
                 aPlacementArea.Init( areaSizeX, areaSizeY );
                 it = vecSubRects.begin();
                 continue;
             }
+        }
 
         // When correctly placed in a placement area, the coords are returned in r.x and r.y
         // Store them.
@@ -212,6 +228,9 @@ void SpreadFootprints( std::vector<MODULE*>* aFootprints,
         footprintListBySheet.clear();
         subsurface = 0.0;
 
+        int fp_max_width = 0;
+        int fp_max_height = 0;
+
         for( unsigned ii = 0; ii < footprintList.size(); ii++ )
         {
             MODULE* footprint = footprintList[ii];
@@ -225,13 +244,21 @@ void SpreadFootprints( std::vector<MODULE*>* aFootprints,
             footprintListBySheet.push_back( footprint );
             subsurface += footprint->GetArea( PADDING );
 
+            // Calculate min size of placement area:
+            EDA_RECT bbox = footprint->GetFootprintRect();
+            fp_max_width = std::max( fp_max_width, bbox.GetWidth() );
+            fp_max_height = std::max( fp_max_height, bbox.GetHeight() );
+
             if( islastItem )
             {
                 // end of the footprint sublist relative to the same sheet path
                 // calculate placement of the current sublist
                 EDA_RECT freeArea;
                 int Xsize_allowed = (int) ( sqrt( subsurface ) * 4.0 / 3.0 );
+                Xsize_allowed = std::max( fp_max_width, Xsize_allowed );
+
                 int Ysize_allowed = (int) ( subsurface / Xsize_allowed );
+                Ysize_allowed = std::max( fp_max_height, Ysize_allowed );
 
                 freeArea.SetWidth( Xsize_allowed );
                 freeArea.SetHeight( Ysize_allowed );
@@ -276,10 +303,17 @@ void SpreadFootprints( std::vector<MODULE*>* aFootprints,
         if( pass == 0 )
         {
             int Xsize_allowed = (int) ( sqrt( placementsurface ) * 4.0 / 3.0 );
+
+            if( Xsize_allowed < 0 || Xsize_allowed > INT_MAX/2 )
+                Xsize_allowed = INT_MAX/2;
+
             int Ysize_allowed = (int) ( placementsurface / Xsize_allowed );
+
+            if( Ysize_allowed < 0 || Ysize_allowed > INT_MAX/2 )
+                Ysize_allowed = INT_MAX/2;
+
             CRectPlacement placementArea;
             CSubRectArray  vecSubRects;
-
             fillRectList( vecSubRects, placementSheetAreas );
             spreadRectangles( placementArea, vecSubRects, Xsize_allowed, Ysize_allowed );
 
@@ -288,6 +322,15 @@ void SpreadFootprints( std::vector<MODULE*>* aFootprints,
                 TSubRect& srect = vecSubRects[it];
                 wxPoint pos( srect.x*scale, srect.y*scale );
                 wxSize size( srect.w*scale, srect.h*scale );
+
+                // Avoid too large coordinates: Overlapping components
+                // are better than out of screen components
+                if( (uint64_t)pos.x + (uint64_t)size.x > INT_MAX/2 )
+                    pos.x = 0;
+
+                if( (uint64_t)pos.y + (uint64_t)size.y > INT_MAX/2 )
+                    pos.y = 0;
+
                 placementSheetAreas[srect.n].SetOrigin( pos );
                 placementSheetAreas[srect.n].SetSize( size );
             }