# 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.
```cpp
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).
```cpp
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?