How to determine whether a particle penetrates a volume？

Particles, Track, Event, Run and Biasing
1

Here is my code

   G4LogicalVolume *pre_volume
                = step->GetPreStepPoint()->GetTouchableHandle()
                        ->GetVolume()->GetLogicalVolume();
        G4VPhysicalVolume *post_phy_volume
                = step->GetPostStepPoint()->GetTouchableHandle()
                        ->GetVolume();
        G4LogicalVolume *post_volume
                = post_phy_volume
                        ->GetLogicalVolume();

        if (post_phy_volume){
       if (post_volume==fScoringVolume1){  G4cout<<" Penetrate"<<G4endl;}
}

But when I run ,the pprogram crashed.
If I delete

   if (post_volume==fScoringVolume1){  G4cout<<" Penetrate"<<G4endl;}

It won’t.
I wanna why

2

Because there is no could be volume in PostStepPoint at the end of modeling steps so you addressing to zero pointer and want to getlLogicalVolume.

4

But the if (post_phy_volume) should make sure that the PhysicalVolume of PostStepPiont is not a nullptr.