From 7b80b2dc7b657cbf6c3a66e4737ab1bf3674708d Mon Sep 17 00:00:00 2001
From: jean-pierre charras <jp.charras@wanadoo.fr>
Date: Sun, 22 Dec 2019 16:19:05 +0100
Subject: [PATCH] Eeschema: fix a crash that sometimes happens with bus
 entries, connected to the same point on a bus. The pointers used in previous
 code could be null, but they were not tested. The pointer validity is now
 tested.

---
 eeschema/connection_graph.cpp | 30 ++++++++++++++++++------------
 eeschema/sch_item.cpp         |  3 ++-
 eeschema/sch_item.h           |  1 +
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/eeschema/connection_graph.cpp b/eeschema/connection_graph.cpp
index c1684fc2fc..b75fa7bd3a 100644
--- a/eeschema/connection_graph.cpp
+++ b/eeschema/connection_graph.cpp
@@ -2015,21 +2015,27 @@ bool CONNECTION_GRAPH::ercCheckBusToBusEntryConflicts( const CONNECTION_SUBGRAPH
     if( bus_entry && bus_entry->m_connected_bus_item )
     {
         bus_wire = bus_entry->m_connected_bus_item;
-        conflict = true;
 
-        auto test_name = bus_entry->Connection( sheet )->Name( true );
-
-        for( const auto& member : bus_wire->Connection( sheet )->Members() )
+        // In some cases, the connection list (SCH_CONNECTION*) can be null.
+        // Skip null connections.
+        if( bus_entry->Connection( sheet ) && bus_wire->Connection( sheet ) )
         {
-            if( member->Type() == CONNECTION_BUS )
+            conflict = true;
+
+            auto test_name = bus_entry->Connection( sheet )->Name( true );
+
+            for( const auto& member : bus_wire->Connection( sheet )->Members() )
             {
-                for( const auto& sub_member : member->Members() )
-                    if( sub_member->Name( true ) == test_name )
-                        conflict = false;
-            }
-            else if( member->Name( true ) == test_name )
-            {
-                conflict = false;
+                if( member->Type() == CONNECTION_BUS )
+                {
+                    for( const auto& sub_member : member->Members() )
+                        if( sub_member->Name( true ) == test_name )
+                            conflict = false;
+                }
+                else if( member->Name( true ) == test_name )
+                {
+                    conflict = false;
+                }
             }
         }
     }
diff --git a/eeschema/sch_item.cpp b/eeschema/sch_item.cpp
index c1de484665..544bdf3f88 100644
--- a/eeschema/sch_item.cpp
+++ b/eeschema/sch_item.cpp
@@ -127,7 +127,8 @@ bool SCH_ITEM::IsConnected( const wxPoint& aPosition ) const
 
 SCH_CONNECTION* SCH_ITEM::Connection( const SCH_SHEET_PATH& aSheet ) const
 {
-    if( m_connection_map.count( aSheet ) )
+    // Warning: the m_connection_map can be empty.
+    if( m_connection_map.size() && m_connection_map.count( aSheet ) )
         return m_connection_map.at( aSheet );
 
     return nullptr;
diff --git a/eeschema/sch_item.h b/eeschema/sch_item.h
index 1810f83953..3cd2edbb93 100644
--- a/eeschema/sch_item.h
+++ b/eeschema/sch_item.h
@@ -327,6 +327,7 @@ public:
 
     /**
      * Retrieves the connection associated with this object in the given sheet
+     * Note: the returned value can be nullptr.
      */
     SCH_CONNECTION* Connection( const SCH_SHEET_PATH& aPath ) const;