Resource Management Audit

Resource Management Audit

Overview

This skill audits resource management to ensure proper cleanup of OpenGL resources, correct IDisposable implementation, and prevention of memory leaks. Focus on engine-specific concerns like OpenGL context safety, factory ownership patterns, and GPU resource tracking.

When to Use

Invoke this skill when:

• Investigating memory leaks or growing memory usage
• GPU resources (textures, buffers) are not being cleaned up
• Adding new resource types (textures, shaders, meshes, framebuffers)
• Refactoring resource lifetime management
• Application crashes on shutdown (disposal issues)
• Out-of-memory errors or GPU resource exhaustion
• Reviewing code for proper disposal patterns

Critical Engine-Specific Rules

1. Never Call OpenGL in Finalizers

Why: OpenGL context is NOT available on finalizer thread. Calling GL functions in finalizers causes crashes.

// ✅ CORRECT - Log warning instead
~Texture()
{
    if (_rendererID != 0)
    {
        Logger.Error($"Texture {_path} not disposed! GPU leak.");
        // Do NOT call GL.DeleteTexture here!
    }
}

public void Dispose()
{
    if (_rendererID != 0)
    {
        GL.DeleteTexture(_rendererID);  // Safe - correct thread
        _rendererID = 0;
    }
    GC.SuppressFinalize(this);  // Prevent finalizer
}

2. Factory-Managed Resources

Rule: Factory owns cached resources. Consumers get references but don't dispose them.

// TextureFactory owns and disposes cached textures
var texture = _textureFactory.Load("sprite.png");

// ❌ WRONG - Don't dispose factory-managed resources
texture.Dispose();  // Other users still need this!

// ✅ CORRECT - Factory disposes on shutdown
// Just use the texture, factory handles lifetime

Check ownership documentation in resource classes (see XML comments).

3. Shared vs. Owned Resources

Owned: Component creates resource exclusively for itself → Component disposes it Shared: Resource comes from factory/cache → Factory disposes it

public class MeshRenderer : IDisposable
{
    private Mesh _mesh;         // Shared (factory-managed)
    private uint _instanceVBO;  // Owned (created by this component)

    public void Dispose()
    {
        // Don't dispose _mesh (shared)

        // DO dispose _instanceVBO (owned)
        if (_instanceVBO != 0)
        {
            GL.DeleteBuffer(_instanceVBO);
            _instanceVBO = 0;
        }
    }
}

4. Disposal Guards

Always implement these safeguards:

public class Texture : IDisposable
{
    private uint _rendererID;
    private bool _disposed = false;

    public void Dispose()
    {
        if (_disposed)          // 1. Guard double-disposal
            return;

        if (_rendererID != 0)   // 2. Check resource exists
        {
            GL.DeleteTexture(_rendererID);
            _rendererID = 0;    // 3. Reset to prevent re-delete
        }

        _disposed = true;
        GC.SuppressFinalize(this);  // 4. Skip finalizer
    }
}

Audit Checklist

When reviewing resource-owning classes, verify:

IDisposable Implementation

• Implements IDisposable
• Has _disposed flag to guard double-disposal
• Resets resource IDs to 0 after deletion
• Calls GC.SuppressFinalize(this) in Dispose()
• Finalizer logs warning (never calls OpenGL)

Ownership Clarity

• Documented who owns the resource (XML comments)
• Shared resources NOT disposed by consumers
• Factory/pool manages disposal of cached resources
• Clear distinction between owned vs. referenced resources

Resource Creation Sites

• Every new Texture() has clear disposal path
• Every GL.GenBuffer() has matching GL.DeleteBuffer()
• Resources created in loops are disposed or cached
• Exception handling doesn't skip disposal (use using or try-finally)

Testing

• Unit tests verify cleanup after load/unload cycles
• ResourceTracker shows stable counters (no growth)
• Shutdown check confirms zero leaks
• Manual testing with RenderDoc (GPU resources)

Common Anti-Patterns

See references/anti-patterns.cs for detailed examples. Quick reference:

1. Missing Disposal: Resource created but never disposed → Add disposal path
2. Double Disposal: No _disposed guard → Crashes on second Dispose()
3. Disposing Shared Resources: Multiple owners unclear → Document ownership
4. OpenGL in Finalizers: Crashes due to missing context → Log warning instead
5. Forgetting GC.SuppressFinalize: Unnecessary finalizer runs → Always call it
6. Wrong Disposal Order: FBO before attachments → Delete in reverse order of creation
7. Null Checks Missing: _mesh.Dispose() crashes if null → Use _mesh?.Dispose()
8. No Disposal Path: Resources in loops → Cache or use using statement

Disposal Patterns Reference

Standard IDisposable patterns with engine-specific notes: references/disposal-patterns.cs

Pattern Selection:

• Basic Pattern: Sealed classes, OpenGL-only resources
• Full Pattern: Inheritable classes, mixed managed/unmanaged resources
• Factory Pattern: Cached/shared resources with centralized lifetime management

Output Format

When reporting audit findings:

**Issue**: [Resource management problem]
**Location**: [File:line]
**Resource Type**: [OpenGL buffer/texture/shader/etc.]
**Problem**: [Specific issue - leak, double disposal, missing cleanup]
**Recommendation**:
[Code example showing fix]
**Priority**: [Critical/High/Medium/Low]

Example:

**Issue**: Mesh resources not disposed when entity destroyed
**Location**: Engine/Scene/Entity.cs:89
**Resource Type**: OpenGL VBO, EBO, VAO
**Problem**: Entity.Destroy() doesn't dispose MeshComponent.Mesh,
causing GPU memory leak (20MB per load/unload cycle)
**Recommendation**:
public void Destroy()
{
    if (HasComponent<MeshComponent>())
    {
        var meshComp = GetComponent<MeshComponent>();
        // Only dispose if component owns the mesh (not factory-managed)
        if (meshComp.OwnsMesh)
        {
            meshComp.Mesh?.Dispose();
        }
        meshComp.Mesh = null;
    }
    _scene.RemoveEntity(this);
}
**Priority**: High (GPU memory leak)

Key Files Reference

• references/disposal-patterns.cs: Standard IDisposable patterns (basic, full, factory)
• references/anti-patterns.cs: 8 common mistakes with ❌/✅ examples

Summary

Core Principles:

1. Never call OpenGL in finalizers (no GL context available)
2. Document ownership explicitly (owned vs. shared resources)
3. Factory-managed resources: factory disposes, consumers reference
4. Always guard double-disposal with _disposed flag
5. Always call GC.SuppressFinalize(this) in Dispose()
6. Use ResourceTracker for leak detection in DEBUG builds
7. Test cleanup with load/unload cycles and shutdown checks