leak-debugging

name	leak-debugging
description	Load when investigating handle leaks, memory leaks, or GC-LEAK failures. Covers handle counting, dotMemory profiling, and GC leak tracker workflows.

Leak Debugging

Specialized workflows for investigating handle leaks, managed memory leaks, and GC leak tracker failures in Skyline tests.

Core Documentation

Read before investigating any leak:

ai/docs/leak-debugging-guide.md - Complete reference covering:

• Handle leak detection and bisection (User/GDI/kernel handles)
• dotMemory profiling for managed memory leaks
• GC leak tracker (GC-LEAK Objects not garbage collected after test:)
• Case studies with step-by-step investigation examples

Quick Reference: Which Leak Type?

Error Message	Type	Section
GC-LEAK Objects not garbage collected after test: SkylineWindow, SrmDocument	GC leak	"GC Leak Tracker" section
Handle counts growing in nightly tests	Handle leak	"Investigation Methodology" section
Memory growing but handles stable	Managed memory leak	"Memory Profiling with dotMemory" section

GC Leak Workflow (Most Common)

When you see GC-LEAK Objects not garbage collected after test::

1. Reproduce locally: Run-Tests.ps1 -TestName <test> — confirm it fails
2. Profile: Run-Tests.ps1 -TestName <test> -MemoryProfile -MemoryProfileWaitRuns 0
3. Ask the user to open the .dmw file in dotMemory GUI and share a screenshot of Key Retention Paths for the leaked type (e.g., SkylineWindow)
4. Read the screenshot to identify the retention chain
5. Fix the retention chain (dispose timers, null delegates, clear caches)
6. Verify: run without profiling to confirm test passes
7. Negative test: comment out fix, confirm test fails again

IMPORTANT: Step 3 requires a human. Do NOT attempt to guess retention paths — dotMemory shows you exactly what's holding the object alive. Guessing wastes time when the answer is one screenshot away.

Handle Leak Workflow

When nightly tests show growing handle counts:

1. Select test: Choose test with highest handles-leaked-per-second ratio
2. Reproduce: Run-Tests.ps1 -TestName <test> -Loop 10 -ReportHandles -SortHandlesByCount
3. Identify type: Which handle category is growing? (User, GDI, kernel)
4. Bisect: Add return; to narrow down which test operation causes the leak
5. Fix and validate: Re-run loop test, confirm handles are stable

Common GC Leak Patterns

Pattern	Example	Fix
Undisposed Timer	UpdateManager Timer in GraphSpectrum	Dispose in OnHandleDestroyed
Static delegate chain	UpgradeManager.AppDeployment → delegates → SkylineWindow	Make holder IDisposable, using pattern
Static tracking list	ReplicateCachingReceiver._cachedSinceTracked	Start/End pattern that nulls the list
Event handler subscription	Component subscribes to long-lived source	Unsubscribe in Dispose

Related Skills

• debugging - General debugging methodology (cycle time, bisection, printf)
• skyline-nightlytests - Query nightly test data for leak trends
• skyline-development - For implementing fixes after isolation