Xcode Memory Graph shows leaks in brand new Kotlin Multiplatform + SwiftUI app (__NSArrayI, __NSCFString, MTLAttributeInternal)

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# Xcode Memory Graph Shows Leaks in Kotlin Multiplatform + SwiftUI App

## Summary
- Xcode Memory Graph reported immediate leaks (`__NSArrayI`, `__NSCFString`, `MTLAttributeInternal`) in a brand-new Kotlin Multiplatform (KMP) + SwiftUI app
- Leaks occur in the default Compose Multiplatform template without custom code
- Memory usage stabilizes over time with no actual growth observed
- Confirmed as false positives in Xcode's instrumentation cache detection

## Root Cause
- Apple's system caches (Metal/Foundation internals) not fully tracked by Xcode Memory Graph:
  - `MTLAttributeInternal`: Metal API shader attribute cache initialization
  - `__NSArrayI`/`__NSCFString`: Foundation framework immutable collection allocations
- SwiftUI + KMP bridging layers trigger initialization of system caches early
- Static KMP framework links to unmanaged CoreFoundation resources

## Why This Happens in Real Systems
- Hybrid SwiftUI/KMP setups activate multiple subsystem caches simultaneously
- Metal API (required by Compose rendering) allocates GPU-related resources
- Xcode interprets unreleased caches as leaks because:
  - Memory Graph doesn't flag system caches as explicitly "safe"
  - Kotlin/Native memory management isn't fully visible to ARC
- Initial cache allocations appear long-lived but remain bounded

## Real-World Impact
- False positives wasting developer debugging time
- Difficulty onboarding new team members to KMP projects
- Erosion of trust in Xcode diagnostics
- No actual effect on runtime stability or memory growth
- Potential masking of real leaks later in development

## Example or Code
Initialization flow triggering Metal cache:

```swift
// ComposeView.swift
struct ComposeView: UIViewControllerRepresentable {
    func makeUIViewController(context: Context) -> UIViewController {
        // Triggers Metal subsystem initialization
        MainViewControllerKt.MainViewController()
    }
}

Xcode-reported leaks:
Memory Graph leak indicators

How Senior Engineers Fix It

  1. Verify leak persistence across multiple relaunches
  2. Correlate with Instruments allocations: 
    instruments -t "Allocations" -leaks app_bundle.app
  3. Check for growth patterns with heap snapshots
  4. Isolate Compose in test view: 
    Text("TEST VIEW").onAppear {
   // Check Leaks without ComposeView
 }
  5. Conditionally disable Metal in Compose: 
    // MainViewController.kt
fun MainViewController(): UIViewController = ComposeUIViewController { 
     App(useSoftwareRendering = true)
}
  6. Suppress false positives via diagnostic ignores

Why Juniors Miss It

  • Over-reliance on Xcode diagnostics as ground truth
  • Misinterpreting clustered system allocations as leaks
  • Lack of Metal API lifecycle awareness
  • Not validating memory growth patterns over time
  • Not isolating framework initialization effects
  • Hesitation to dismiss profiling tool warnings