Skill: Memory Management & Object Lifecycle

This skill provides guidelines for managing memory safely within the uLib framework to prevent memory corruption and leaks.

Context

Ownership: ObjectsContext typically owns its children.
Shared Access: Use SmartPointer<T> for objects shared across multiple systems (e.g., Geant4 and VTK).
Core Principle: Avoid manual delete on objects managed by the framework.

Patterns

1. Context Ownership

When an object is added to an ObjectsContext, it is managed by that context.

auto* context = new ObjectsContext();
auto* obj = new MyObject();
context->AddObject(obj); 
// Do NOT delete obj; it will be deleted when context is destroyed.

2. Smart Pointers

Use SmartPointer<T> for resources like Material or Solid that are used by both domain logic and external engines (Geant4).

uLib::SmartPointer<Material> mat = new Material("Lead");
solid->SetMaterial(mat); // Shared ownership

3. Geant4 Object Safety

Geant4 often takes ownership of certain objects (like G4VPhysicalVolume). When wrapping these:

Ensure the wrapper doesn't double-free the Geant4-owned pointer.
Use recursion_guard if synchronizing transformations between uLib::Object and Geant4 volumes to prevent signal loops.

Debugging Memory Issues

SIGABRT (invalid pointer): Usually caused by deleting an object that was already managed (and deleted) by an ObjectsContext or SmartPointer.
Leaks: Check if objects were created but never added to a context or wrapped in a SmartPointer.

Checklist

Are objects added to an ObjectsContext?
Is SmartPointer used for shared resources?
Is there a risk of double-freeing Geant4-managed pointers?

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