How to Use Memgraph for iOS Memory Leak Detection with the Build iOS Apps Plugin

The Build iOS Apps plugin provides an automated iOS Memgraph Leaks skill that captures heap snapshots from iOS simulators and generates markdown reports to identify and root-cause memory leaks.

The openai/plugins repository includes a specialized Build iOS Apps plugin that streamlines memory debugging for iOS applications. By leveraging the iOS Memgraph Leaks skill, developers can automate the capture and analysis of heap snapshots to detect retain cycles and unreachable objects without manual profiling in Xcode. This workflow integrates directly into CI pipelines, treating memory analysis as a reproducible quality gate rather than ad-hoc debugging.

Understanding iOS Memgraph Snapshots

A memgraph is a binary-format snapshot of an iOS app's heap taken from a running simulator process. Unlike live debugging sessions, memgraph files provide deterministic snapshots that can be archived, compared across builds, and analyzed offline using macOS command-line tools. The Build iOS Apps plugin treats these snapshots as test artifacts, enabling regression verification and historical leak tracking.

Automated Leak Detection Workflow

The iOS Memgraph Leaks skill automates a three-stage workflow designed for iterative debugging: capture, summarize, and investigate.

Capture Memgraph from Simulator

The capture_sim_memgraph.sh script wraps Xcode's xcrun memgraph tool to extract heap data from a specific simulator instance. Located at plugins/build-ios-apps/skills/ios-memgraph-leaks/scripts/capture_sim_memgraph.sh, this script requires the target simulator UDID and app bundle identifier to produce a timestamped .memgraph file.

SKILL_DIR="/path/to/plugins/build-ios-apps/skills/ios-memgraph-leaks"
SIM="F2E3A4B5-1234-5678-90AB-CDEF12345678"
BUNDLE_ID="com.example.myapp"
MEMGRAPH_DIR="$(mktemp -d "${TMPDIR:-/tmp}/codex-ios-memgraph.XXXXXX")"

"$SKILL_DIR/scripts/capture_sim_memgraph.sh" \
  --udid "$SIM" \
  --bundle-id "$BUNDLE_ID" \
  --out-dir "$MEMGRAPH_DIR"

Summarize Leaks with Python Analysis

After capture, the summarize_memgraph_leaks.py script parses the memgraph using the macOS leaks command. This Python helper, found at plugins/build-ios-apps/skills/ios-memgraph-leaks/scripts/summarize_memgraph_leaks.py, generates a structured markdown report containing total leak counts, top offending types, individual leak entries, and grouped-by-type trees for unreachable retain cycles.

"$SKILL_DIR/scripts/summarize_memgraph_leaks.py" \
  "$MEMGRAPH_DIR/<timestamp>.memgraph" \
  --trace-limit 5 \
  --out "./leak-summary.md"

The --trace-limit parameter controls how many leaks --traceTree excerpts appear in the report, providing immediate context for the most critical leaks without overwhelming noise.

Root-Cause Investigation

For leaked objects identified in the summary, use leaks --traceTree=<address> to reveal ownership paths and retain cycles. If traceTree returns no roots, the leaks --groupByType flag helps categorize unreachable objects by their class types. The skill's documentation in SKILL.md recommends iterating through these steps: apply the smallest possible fix, recapture the memgraph, and compare before/after results to verify the elimination of specific leak signatures rather than merely reducing total counts.

leaks --traceTree=0x12345678 "$MEMGRAPH_DIR/<timestamp>.memgraph"

Integrating into Development Workflows

Because memgraph snapshots are deterministic binary artifacts, teams can store them alongside test results in CI pipelines. The workflow documented in plugins/build-ios-apps/skills/ios-memgraph-leaks/SKILL.md emphasizes a repeatable five-step process:

1. Build and drive the target UI flow that should release objects
2. Capture the memgraph from the simulator
3. Summarize the memgraph with the Python script
4. Inspect app-owned leaks with leaks --traceTree
5. Verify fixes through comparative analysis of recaptured snapshots

This approach transforms memgraph for iOS memory leak detection from manual investigation into a reproducible engineering practice.

Summary

• Memgraph snapshots provide deterministic binary heap captures from iOS simulators, enabling offline analysis and CI integration.
• The capture script (capture_sim_memgraph.sh) automates xcrun memgraph execution using simulator UDID and bundle identifiers.
• The summarization script (summarize_memgraph_leaks.py) parses leaks command output into actionable markdown reports with configurable trace limits.
• Root-cause analysis uses leaks --traceTree for ownership paths and leaks --groupByType for categorizing unreachable retain cycles.
• The complete workflow is documented in plugins/build-ios-apps/skills/ios-memgraph-leaks/SKILL.md within the openai/plugins repository.

Frequently Asked Questions

What is the difference between a memgraph file and Xcode's Memory Graph Debugger?

A memgraph file is a binary snapshot saved to disk, whereas Xcode's Memory Graph Debugger provides a live, interactive visualization. The memgraph format enables automated analysis in CI environments and allows engineers to compare heap states across different builds or code changes using command-line tools like leaks.

Can I use the iOS Memgraph Leaks skill on physical devices?

No. According to the source implementation in openai/plugins, the capture_sim_memgraph.sh script specifically targets iOS simulators using xcrun simctl and simulator UDIDs. Physical device memory debugging requires different entitlements and transfer mechanisms not supported by this particular skill.

How do I interpret when leaks --traceTree returns no root information?

When traceTree finds no ownership roots for a leaked object, use the leaks --groupByType flag to categorize leaks by their Objective-C or Swift class names. This often reveals systemic retain cycles within specific modules or third-party frameworks, as documented in the skill's SKILL.md troubleshooting section.

Is the Python summarization script compatible with custom memgraph files captured manually?

Yes. While designed to work with the capture script's output, summarize_memgraph_leaks.py accepts any valid .memgraph file path as its positional argument. You can generate memgraphs manually via Xcode's "Debug Memory Graph" export feature or xcrun memgraph and still process them through the summarization pipeline for consistent reporting.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}