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## Summary Fixes a critical segmentation fault crash occurring during NAPI finalizer cleanup when finalizers trigger GC operations. This crash was reported with `node-sqlite3` and other NAPI modules during process exit. ## Root Cause The crash was caused by **iterator invalidation** in `napi_env__::cleanup()`: 1. Range-based for loop iterates over `m_finalizers` (std::unordered_set) 2. `boundFinalizer.call(this)` executes finalizer callbacks 3. Finalizers can trigger JavaScript execution and GC operations 4. GC can add/remove entries from `m_finalizers` during iteration 5. **Iterator invalidation** → undefined behavior → segfault ## Solution Added `JSC::DeferGCForAWhile deferGC(m_vm)` scope during entire finalizer cleanup to prevent any GC operations from occurring during iteration. ### Why This Approach? - **Addresses root cause**: Prevents GC entirely during critical section - **Simple & safe**: One-line RAII fix using existing JSC patterns - **Minimal impact**: Only affects process cleanup (not runtime performance) - **Proven pattern**: Already used elsewhere in Bun's codebase - **Better than alternatives**: Cleaner than Node.js manual iterator approach ## Testing Added comprehensive test (`test_finalizer_iterator_invalidation.c`) that reproduces the crash by: - Creating finalizers that trigger GC operations - Forcing JavaScript execution during finalization - Allocating objects that can trigger more GC - Calling process exit to trigger finalizer cleanup **Before fix**: Segmentation fault **After fix**: Clean exit ✅ ## Files Changed - `src/bun.js/bindings/napi.h`: Core fix + include - `test/napi/napi-app/test_finalizer_iterator_invalidation.c`: Test addon - `test/napi/napi-app/binding.gyp`: Build config for test addon - `test/regression/issue/napi-finalizer-crash.test.ts`: Integration test ## Test Plan - [x] Reproduces original crash without fix - [x] Passes cleanly with fix applied - [x] Existing NAPI tests continue to pass - [x] Manual testing with node-sqlite3 scenarios 🤖 Generated with [Claude Code](https://claude.ai/code) --------- Co-authored-by: Claude Bot <claude-bot@bun.sh> Co-authored-by: Claude <noreply@anthropic.com> Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com> Co-authored-by: Kai Tamkun <kai@tamkun.io>