Updates requested in PR 110: Added comments.

Author: marek-trtik

src/taint-slicer/propagation_chains.cpp

@@ -279,19 +279,29 @@ taint_propagation_chainst::erase_node(const node_idt nid)
   }
 
   for(const auto &pred_nid : get_predecessors_map().at(nodes.size()))
-    if(pred_nid!=nodes.size())
+    if(pred_nid!=nodes.size()) // We have to exclude here the situation, when
+                               // the node 'nodes.size()' (i.e. the one
+                               // replacing the removed node 'nid') is its own
+                               // predecessor. We handle that situation later.
     {
       auto &edges=successors.at(pred_nid);
       edges[nid].insert(edges[nodes.size()].begin(), edges[nodes.size()].end());
       edges.erase(nodes.size());
     }
   for(const auto &nid_fns : get_successors_map().at(nodes.size()))
-    if(nid_fns.first!=nodes.size())
+    if(nid_fns.first!=nodes.size()) // We have to exclude here the situation,
+                                    // when the node 'nodes.size()' (i.e. the
+                                    // one replacing the removed node 'nid')
+                                    // is its own predecessor. We handle that
+                                    // situation later.
     {
       auto &edges=predecessors.at(nid_fns.first);
       edges.insert(nid);
       edges.erase(nodes.size());
     }
+  // Here we handle the situation, when the node 'nodes.size()' (i.e. the one
+  // replacing the removed node 'nid') is its own predecessor and successor
+  // (i.e. when this node has a loop edge).
   if(get_predecessors_map().at(nodes.size()).count(nodes.size())!=0UL)
   {
     {
@@ -305,6 +315,9 @@ taint_propagation_chainst::erase_node(const node_idt nid)
       edges.erase(nodes.size());
     }
   }
+  // Now we finally remove in- and out-edges of the node 'nid' (by replacing
+  // them by the last node 'nodes.size()', which will become the new node
+  // 'nid').
   successors.at(nid)=successors.at(nodes.size());
   successors.erase(nodes.size());
   predecessors.at(nid)=predecessors.at(nodes.size());