--- name: 1k-patching-native-modules description: Patches native modules (expo-image, react-native, etc.) to fix native crashes or bugs. disable-model-invocation: true --- # Patching Native Modules Follow this workflow to analyze crash logs, fix native module bugs, and generate patches. ## Workflow Overview ``` 1. Analyze Crash Log → 2. Locate Bug → 3. Fix Code → 4. Clean Build Artifacts → 5. Generate Patch → 6. Commit & PR ``` ## Step 1: Analyze Crash Log ### iOS Crash (EXC_BAD_ACCESS / KERN_INVALID_ADDRESS) Key information to extract: - **Exception type**: `EXC_BAD_ACCESS`, `SIGABRT`, etc. - **Stack trace**: Identify the crashing function - **Memory address**: Helps identify nil pointer issues - **Library**: Which native module is crashing Example crash pattern: ``` EXC_BAD_ACCESS: KERN_INVALID_ADDRESS at 0x3c61c1a3b0d0 objc_msgSend in unknown file -[SDWebImageManager cacheKeyForURL:context:] ← Crashing function -[SDWebImageManager loadImageWithURL:options:context:progress:completed:] ``` ### Android Crash (NullPointerException / OOM) Look for: - **Exception class**: `NullPointerException`, `OutOfMemoryError` - **Stack trace**: Java/Kotlin method chain - **Thread info**: Main thread vs background ## Step 2: Locate the Bug ### Find native module source ```bash # iOS (Swift/Objective-C) ls node_modules//ios/ # Android (Kotlin/Java) ls node_modules//android/src/main/java/ ``` ### Common crash causes | Crash Type | Common Cause | Fix Pattern | |------------|--------------|-------------| | `EXC_BAD_ACCESS` | Nil pointer dereference | Add `guard let` check | | `KERN_INVALID_ADDRESS` | Accessing deallocated memory | Use weak references | | `NullPointerException` | Null object access | Add null check | | `OutOfMemoryError` | Large image/data processing | Add size limits | ## Step 3: Fix the Code ### iOS (Swift) - Nil Check Pattern ```swift // Before (crashes when uri is nil) imageManager.loadImage(with: source.uri, ...) // After (safe) guard let sourceUri = source.uri, !sourceUri.absoluteString.isEmpty else { onError(["error": "Image source URI is nil or empty"]) return } imageManager.loadImage(with: sourceUri, ...) ``` ### Android (Kotlin) - Null Check Pattern ```kotlin // Before val uri = source.uri loadImage(uri) // After val uri = source.uri ?: return if (uri.toString().isEmpty()) return loadImage(uri) ``` ## Step 4: Clean Build Artifacts (CRITICAL) **Before generating patch, MUST clean Android build cache:** ```bash # Remove Android build artifacts to avoid polluting the patch rm -rf node_modules//android/build # For expo-image specifically: rm -rf node_modules/expo-image/android/build ``` Why this matters: - Android build generates `.class`, `.jar`, binary files - These pollute the patch file (can grow to 5000+ lines) - patch-package will include these unwanted files ## Step 5: Generate Patch ```bash # Generate patch file npx patch-package # Example: npx patch-package expo-image ``` Patch file location: `patches/+.patch` ### Verify patch content ```bash # Check patch doesn't include unwanted files grep -c "android/build" patches/*.patch # Should return 0 # View actual changes head -100 patches/*.patch ``` ## Step 6: Commit & Create PR ```bash # Stage patch file git add patches/*.patch # Commit with descriptive message git commit -m "fix(ios): prevent EXC_BAD_ACCESS crash in when Add guard checks in native layer to prevent crash when . Fixes Sentry issue #XXXXX" # Create PR gh pr create --title "fix(ios): " --base x ``` ## Common Packages & Their Native Locations | Package | iOS Source | Android Source | |---------|------------|----------------| | `expo-image` | `node_modules/expo-image/ios/` | `node_modules/expo-image/android/src/` | | `react-native` | `node_modules/react-native/React/` | `node_modules/react-native/ReactAndroid/` | | `@react-native-async-storage/async-storage` | `node_modules/@react-native-async-storage/async-storage/ios/` | `...android/src/` | | `react-native-reanimated` | `node_modules/react-native-reanimated/ios/` | `...android/src/` | ## Existing Patches Reference Check existing patches for patterns: ```bash ls patches/ cat patches/expo-image+3.0.10.patch ``` ## Troubleshooting ### Patch file too large ```bash # Clean all build artifacts rm -rf node_modules//android/build rm -rf node_modules//ios/build rm -rf node_modules//.gradle # Regenerate npx patch-package ``` ### Patch not applying ```bash # Check package version matches cat node_modules//package.json | grep version # Rename patch if version changed mv patches/+old.patch patches/+new.patch ``` ### Swift/Kotlin syntax help **Swift guard let:** ```swift guard let value = optionalValue else { return // Must exit scope } // value is now non-optional ``` **Kotlin null check:** ```kotlin val value = nullableValue ?: return // value is now non-null ``` ## Related Files - Patches directory: `patches/` - expo-image iOS: `node_modules/expo-image/ios/ImageView.swift` - expo-image Android: `node_modules/expo-image/android/src/main/java/expo/modules/image/`

1k-patching-native-modules

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