Avoid updating max clearance while in dtor

Max clearance is updated by IncrementTimeStamp(), which is called when in the FOOTPRINT dtor and ZONE dtor.  This can cause issues when iterating over all footprints as the footprints may be delete-ed

Fixes https://gitlab.com/kicad/code/kicad/issues/17269

pcbnew/board.cpp

@@ -80,7 +80,7 @@ BOARD::BOARD() :
         m_project( nullptr ),
         m_userUnits( EDA_UNITS::MILLIMETRES ),
         m_designSettings( new BOARD_DESIGN_SETTINGS( nullptr, "board.design_settings" ) ),
-        m_deleting( false ),
+        m_skipMaxClearanceCacheUpdate( false ),
         m_maxClearanceValue( 0 ),
         m_NetInfo( this )
 {
@@ -133,7 +133,7 @@ BOARD::BOARD() :
 
 BOARD::~BOARD()
 {
-    m_deleting = true;
+    m_skipMaxClearanceCacheUpdate = true;
 
     // Untangle group parents before doing any deleting
     for( PCB_GROUP* group : m_groups )
@@ -780,8 +780,8 @@ BOARD_DESIGN_SETTINGS& BOARD::GetDesignSettings() const
 
 void BOARD::UpdateMaxClearanceCache()
 {
-    // in destructor, useless work
-    if( m_deleting )
+    // in destructor or otherwise reasonable to skip
+    if( m_skipMaxClearanceCacheUpdate )
         return;
 
     int worstClearance = m_designSettings->GetBiggestClearanceValue();
@@ -1121,10 +1121,14 @@ void BOARD::DeleteMARKERs( bool aWarningsAndErrors, bool aExclusions )
 
 void BOARD::DeleteAllFootprints()
 {
+    m_skipMaxClearanceCacheUpdate = true;
+
     for( FOOTPRINT* footprint : m_footprints )
         delete footprint;
 
     m_footprints.clear();
+    m_skipMaxClearanceCacheUpdate = false;
+    UpdateMaxClearanceCache();
 }
 
 

pcbnew/board.h

@@ -1320,7 +1320,7 @@ private:
      */
     bool                         m_legacyTeardrops = false;
 
-    bool                         m_deleting;        // inside destructor
+    bool                         m_skipMaxClearanceCacheUpdate;
     int                          m_maxClearanceValue;  // cached value
 
     NETINFO_LIST                 m_NetInfo;         // net info list (name, design constraints...