Segmentation fault in Stepping Action Class

[surajsinghdeos]

This is my StepingAction Class:

#include "MySteppingAction.hh"
#include "MyEventAction.hh" 
#include "G4Step.hh"
#include "G4TouchableHistory.hh"
#include "G4Track.hh"
#include "G4ParticleDefinition.hh"
#include "G4IonTable.hh"
#include "G4ParticleTypes.hh"  
#include <iostream>
MySteppingAction::MySteppingAction(MyEventAction* eventAction) : eventAction(eventAction) {}

MySteppingAction::~MySteppingAction(){}
void MySteppingAction::UserSteppingAction(const G4Step* step) {
	G4Track* track = step->GetTrack();
	G4ParticleDefinition* particle = track->GetDefinition();

	G4VPhysicalVolume* nextVol =  track->GetNextVolume();
	G4VPhysicalVolume* Vol =  track->GetVolume();

	std::cout << Vol->GetName() << "\t" << nextVol->GetName() << std::endl;

	// Check if the particle is an ion
	if (particle->GetParticleType() != "nucleus") {
		// Kill the track if it is not an ion
		track->SetTrackStatus(fStopAndKill);
	}

}

And this code is working fine if I comment this line of above code:

std::cout << Vol->GetName() << “\t” << nextVol->GetName() << std::endl;

And if I uncomment this, it throws segmentation fault like shown in the attached figure.

May someone tell me what is problem with code here?

[mkelsey]

When the track leaves the world, there is no “next volume,” so GetNextVolume() returns a null pointer. It is your responsibility, when writing your code, to check for null pointers before dereferencing them.