router: prevent a very unlikely infinite loop in PNS::LINE::Walkaround() causing an OOM&segfault

Fixes: lp:1767587
* https://bugs.launchpad.net/kicad/+bug/1767587

pcbnew/router/pns_line.cpp

@@ -166,7 +166,7 @@ bool LINE::Walkaround( SHAPE_LINE_CHAIN aObstacle, SHAPE_LINE_CHAIN& aPre,
     if( aObstacle.PointInside( line.CPoint( 0 ) ) || aObstacle.PointInside( line.CPoint( -1 ) ) )
         return false;
 
-    SHAPE_LINE_CHAIN::INTERSECTIONS ips, ips2;
+    SHAPE_LINE_CHAIN::INTERSECTIONS ips;
 
     line.Intersect( aObstacle, ips );
 
@@ -226,6 +226,9 @@ bool LINE::Walkaround( SHAPE_LINE_CHAIN aObstacle, SHAPE_LINE_CHAIN& aPre,
 
     int i = i_first;
 
+    if( i_first < 0 || i_last < 0 )
+        return false;
+
     while( i != i_last )
     {
         aWalk.Append( aObstacle.CPoint( i ) );
@@ -249,14 +252,18 @@ bool LINE::Walkaround( SHAPE_LINE_CHAIN aObstacle, SHAPE_LINE_CHAIN& aPre,
 }
 
 
-void LINE::Walkaround( const SHAPE_LINE_CHAIN& aObstacle, SHAPE_LINE_CHAIN& aPath, bool aCw ) const
+bool LINE::Walkaround( const SHAPE_LINE_CHAIN& aObstacle, SHAPE_LINE_CHAIN& aPath, bool aCw ) const
 {
     SHAPE_LINE_CHAIN walk, post;
 
-    Walkaround( aObstacle, aPath, walk, post, aCw );
+    if( ! Walkaround( aObstacle, aPath, walk, post, aCw ) )
+        return false;
+
     aPath.Append( walk );
     aPath.Append( post );
     aPath.Simplify();
+
+    return true;
 }
 
 

pcbnew/router/pns_line.h

@@ -236,7 +236,7 @@ public:
             SHAPE_LINE_CHAIN& aPost,
             bool aCw ) const;
 
-    void Walkaround( const SHAPE_LINE_CHAIN& aObstacle,
+    bool Walkaround( const SHAPE_LINE_CHAIN& aObstacle,
             SHAPE_LINE_CHAIN& aPath,
             bool aCw ) const;
 

pcbnew/router/pns_shove.cpp

@@ -135,8 +135,11 @@ SHOVE::SHOVE_STATUS SHOVE::walkaroundLoneVia( LINE& aCurrent, LINE& aObstacle,
     const SHAPE_LINE_CHAIN hull = aCurrent.Via().Hull( clearance, aObstacle.Width() );
     SHAPE_LINE_CHAIN path_cw, path_ccw;
 
-    aObstacle.Walkaround( hull, path_cw, true );
-    aObstacle.Walkaround( hull, path_ccw, false );
+    if( ! aObstacle.Walkaround( hull, path_cw, true ) )
+        return SH_INCOMPLETE;
+
+    if( ! aObstacle.Walkaround( hull, path_ccw, false ) )
+        return SH_INCOMPLETE;
 
     const SHAPE_LINE_CHAIN& shortest = path_ccw.Length() < path_cw.Length() ? path_ccw : path_cw;
 
@@ -178,7 +181,9 @@ SHOVE::SHOVE_STATUS SHOVE::processHullSet( LINE& aCurrent, LINE& aObstacle,
         {
             const SHAPE_LINE_CHAIN& hull = aHulls[invertTraversal ? aHulls.size() - 1 - i : i];
 
-            l.Walkaround( hull, path, clockwise );
+            if( ! l.Walkaround( hull, path, clockwise ) )
+                return SH_INCOMPLETE;
+
             path.Simplify();
             l.SetShape( path );
         }

pcbnew/router/pns_walkaround.cpp

@@ -79,10 +79,13 @@ WALKAROUND::WALKAROUND_STATUS WALKAROUND::singleStep( LINE& aPath,
         }
     }
 
-    aPath.Walkaround( current_obs->m_hull, path_pre[0], path_walk[0],
-                      path_post[0], aWindingDirection );
-    aPath.Walkaround( current_obs->m_hull, path_pre[1], path_walk[1],
-                      path_post[1], !aWindingDirection );
+    if( ! aPath.Walkaround( current_obs->m_hull, path_pre[0], path_walk[0],
+                      path_post[0], aWindingDirection ) )
+        return STUCK;
+
+    if( ! aPath.Walkaround( current_obs->m_hull, path_pre[1], path_walk[1],
+                      path_post[1], !aWindingDirection ) )
+        return STUCK;
 
 #ifdef DEBUG
     m_logger.NewGroup( aWindingDirection ? "walk-cw" : "walk-ccw", m_iteration );