I have a program which constructs a G4MassGeometrySampler within a G4VUserDetectorConstruction derived class (call it MyUDC). When I delete the G4RunManager it calls in sequence ... G4ParticleTable::GetParticleTable()->DeleteMessenger(); ... delete userDetector; DeleteMessenger() deletes the entire particle table. "delete userDetector" calls MyUDC::~MyUDC which calls "delete mgs" (a G4MassGeometrySampler). Tracing this I found that G4MassGeometrySampler::~G4MassGeometrySampler -> G4MImportanceConfigurator::~G4MImportanceConfigurator() -> G4ProcessPlacer::RemoveProcess(G4VProcess*) -> G4ProcessPlacer::PrintPostStepGPILVec() -> G4ProcessPlacer::GetProcessManager(). This last function calls G4ParticleTable::GetParticleTable() which is already gone. There is no testing to determine whether the pointer to the Particle Table actually receives a meaningful memory location. I'm not exactly sure if the segmentation error occurs within this function or within GetParticleTable() . If the ParticleTable doesn't exist, then GetProcessManager() should return NULL which then should be dealt with appropriately by the calling functions. If it throws an exception, then it could kill a program trying to normally delete. This problem is easily reproducible by adding the line delete runManager; right before the last curly brace into exampleB01.cc (in examples/extended/biasing/B01/). It turns out the issue is normally skirted in exampleB01 because c++ automatically calls the destructors in the correct order (i.e. G4MassGeometrySampler and then G4RunManager).
problem occurs because the mass geometry sampler destructor does not get called into it goes out of scope - program exits. As the runManager has already deleted the processes this causes the segmentation fault. The fix is as follows: Add the line: mgs.ClearSampling() delete runManager; before the return 0; at the end of the main program and everything closes properly. The reason the particle table is not checked before deleting a process is that processes are attached to particles, therefore to delete an abstract process with no particle is meaningless. I hope this also fixes the user's application code.
