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Colby Mchenry
838006c947
Fixes #1581.
## What was wrong
`codegraph init` / `codegraph index` died with `Segmentation fault` — the whole CLI
process, not a parse worker — on a C/C++ file with very deep brace nesting (llvm's
`clang/test/Parser/parser_overflow.c`, 16,384 nested `{`). The reporter's diagnosis is
exactly right: tree-sitter's parser is iterative, so the file parses fine, and then the
native kernel's **recursive walker** (`visit_node` → `visit_for_calls_and_structure` → …,
one frame per AST level) overflowed the thread's stack. A native overflow can't be caught
the way a wasm abort can, and a parse worker is a thread of the `codegraph` process, so
the SIGSEGV took the entire indexer down — no message, no per-file fallback, no partial
index.
Two things made "just give the worker a bigger stack" the wrong fix:
- it only moves the cliff — reproduced here: the reporter's 16,384-deep file kills a
default 4 MiB worker (rc=132 on macOS / 139 on Linux), and a 100k-deep file kills the
8 MiB **main** thread too;
- the walkers are shared by every kernel-routed language (20 of them), and each has
several recursion points with different frame sizes, so no single stack size is a
provable bound.
Meanwhile the wasm path already handles this shape gracefully: its JS walker catches its
own `RangeError` per file and stores a partial result with a `parse_error`. The kernel
just needed a way to get there instead of dying.
## What this does
**The kernel guards its own recursion against the calling thread's real stack bounds and
defers a too-deep file to wasm** — the same `defer:` routing signal it already uses for
files with parse errors, which `src/extraction/kernel/index.ts` treats as "take the wasm
path for this file", silently.
- `codegraph-kernel/src/stack.rs`: per-thread stack bounds from the OS, computed once per
thread and cached — glibc/musl `pthread_getattr_np` + `pthread_attr_getstack`, macOS
`pthread_get_stackaddr_np` + `pthread_get_stacksize_np`, Win32
`GetCurrentThreadStackLimits` (a hand-declared `kernel32` extern; no `windows-sys`).
`exhausted()` is one thread-local load and one compare: true once the stack pointer is
within a 256 KiB red zone of the limit, and it latches a flag. Where the OS can't report
bounds it falls back to a fixed 1 MiB descent budget measured from the entry stack
pointer — safe on anything from Node's 4 MiB worker default up. So the guard is exact on
the 4 MiB worker, the 8 MiB main thread, and any `resourceLimits.stackSizeMb` alike.
- `stack_guard!()` (defined in `lib.rs`) is the first statement of every recursive walker
function — all **150** self-recursive or on-cycle functions across the 15 walker modules,
found by script (every cycle in the call graph, not just direct self-calls). It returns
`Default::default()` (`()`, `false`, `None`, `""`) so an exhausted walk simply stops
descending; a hook returning `false` sends its caller down the generic child walk, whose
own guard returns at once.
- `extract_file` runs the whole walk under `stack::run_guarded`: if the flag is set
afterwards the (truncated) result is discarded and replaced by
`defer: nesting too deep for the native walker — wasm recovery handles it`.
- `parse-pool.ts`: a comment at `new Worker(scriptPath)` records why there is deliberately
no `resourceLimits.stackSizeMb` bump.
- No new crates beyond `libc` as a direct unix dependency (already in `Cargo.lock`
transitively). No wire/ABI change.
Net effect for the reporter's repo: `deep.c` goes to the wasm path, lands as
`function foo` plus a recorded parse warning, and the other 31,607 files index normally.
`CODEGRAPH_KERNEL=0` and the `exclude` workaround are no longer needed.
## Tests
**Rust unit tests** (`cargo test`, 21 passed — 7 new in `stack.rs`): the walkers for
C, C++, Rust, TypeScript and Python are driven on a **1 MiB** thread (a quarter of Node's
worker default) with 30k-deep nesting and must return `defer:` instead of crashing;
shallow files are untouched; the latch resets between runs; the OS bounds are sane on the
main thread and describe a small thread's own stack.
**`__tests__/kernel-deep-nesting.test.ts`** (new, 8 tests — skips without a staged `.node`,
fails under `CODEGRAPH_KERNEL_EXPECT=1` if the kernel is missing, like the other kernel
suites):
- every default-routed language (all 20) survives a 60k-deep expression on the main thread
— clean result or the wasm fallback's partial result, never a crash;
- the reporter's exact 16,384-brace C file is indexed (partial) on the main thread;
- 200-deep expressions in every language still take the kernel path clean (the guard never
trips on normal code);
- inside a **default-sized 4 MiB `worker_threads` Worker** through `dist/`: the reporter's
`deep.c` and a 60k-deep expression in every language come back `deferred` with exit 0,
and a normal file still extracts natively;
- end-to-end through the built CLI: `codegraph init` on a repo holding `deep.c` + `ok.c`
exits 0 and records both files, with both functions.
**Existing kernel suites**: all 15 (`kernel-*-parity`, `kernel-scaffold`,
`kernel-retry-materialize`, `kernel-grammar-parity`) pass unchanged, 147 tests — the guard
never fires on the parity fixtures.
**Reporter's probes** (`one.js` from the issue, default 4 MiB worker, this build):
`deep.c` → `deferred`, exitCode=0 (was rc=132/139); `deep100k.c` → `deferred`, exitCode=0.
Main thread: `deep.c` / `deep100k.c` → wasm partial with
`Parse error: Maximum call stack size exceeded`; a 6,000-term binary expression and a
3,000-branch `else if` chain stay on the kernel path with clean results.
**Perf** (same `dist/`, only the `.node` swapped via `CODEGRAPH_KERNEL_PATH`; interleaved
main/new ×3, `codegraph init`, macOS arm64):
| repo | main (median) | guarded (median) | nodes / edges |
|---|---|---|---|
| express (141 files) | 0.60 s (0.58–0.65) | 0.61 s (0.58–0.61) | 1,084 / identical |
| redis (786 C/H files) | 4.44 s (4.39–4.66) | 4.49 s (4.41–4.70) | 19,942 / 76,446 identical |
Within run-to-run noise, as expected for one TLS load + compare per recursion entry.
**Linux (Docker, `node:22-bookworm`, kernel built in-container, `docker run --rm --init`)** —
the reporter's platform and the glibc `pthread_getattr_np` bounds path:
```
=== platform ===
Linux efe3cc86947b 6.12.54-linuxkit #1 SMP Tue Nov 4 21:21:47 UTC 2025 aarch64 GNU/Linux
v22.22.3
-rwxr-xr-x 1 root root 35332288 Aug 22 18:02 codegraph-kernel/prebuilds/linux-arm64/codegraph-kernel.node
=== reporter repro (issue #1581): 16,384-brace deep.c, codegraph init ===
│
└ Done
init exit code: 0
file: deep.c
file: deep100k.c
file: ok.c
function: add
function: bar
function: foo
=== worker probe: kernel raw extract in a default 4 MiB worker ===
deep.c: deferred
deep.c: worker exitCode=0
deep100k.c: deferred
deep100k.c: worker exitCode=0
ok.c: kernel nodes=2
ok.c: worker exitCode=0
=== cargo test stack:: (glibc pthread_getattr_np bounds path) ===
test stack::tests::os_bounds_are_sane_on_this_platform ... ok
test stack::tests::small_stack_reports_its_own_bounds ... ok
test stack::tests::normal_files_are_untouched_by_the_guard ... ok
test stack::tests::deep_braces_c_defer_instead_of_crashing ... ok
test stack::tests::latch_resets_between_runs ... ok
test stack::tests::deep_parens_cpp_rust_ts_python_defer_instead_of_crashing ... ok
test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 15 filtered out; finished in 0.23s
=== vitest: kernel-deep-nesting + kernel-scaffold ===
✓ __tests__/kernel-scaffold.test.ts (10 tests) 30ms
✓ __tests__/kernel-deep-nesting.test.ts (8 tests) 36989ms
Test Files 2 passed (2)
Tests 18 passed (18)
```
(The pre-fix crash was reproduced on macOS — rc=132 in a default worker, rc=139 on the main thread at 100k depth — not re-run inside this container; the reporter's Linux x86_64 trace is the SIGSEGV form of the same overflow.)
**Windows (Parallels ARM64 VM, MSVC 14.44, `cargo 1.97`, kernel built on the VM,
`GetCurrentThreadStackLimits` path)**:
```
head: cbf8485 fix(kernel): guard the native walkers against stack overflow and defer deep files to wasm (#1581)
=== cargo build --release (win32-arm64) ===
Finished `release` profile [optimized] target(s) in 2m 04s
staged: 35086848 bytes
=== cargo test (stack guard unit tests) ===
test stack::tests::normal_files_are_untouched_by_the_guard ... ok
test stack::tests::os_bounds_are_sane_on_this_platform ... ok
test stack::tests::small_stack_reports_its_own_bounds ... ok
test stack::tests::deep_braces_c_defer_instead_of_crashing ... ok
test stack::tests::latch_resets_between_runs ... ok
test stack::tests::deep_parens_cpp_rust_ts_python_defer_instead_of_crashing ... ok
test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 15 filtered out; finished in 0.49s
=== reporter repro: codegraph init on a 16,384-brace deep.c ===
└ Done
init exit code: 0
=== vitest: deep-nesting + scaffold (CODEGRAPH_KERNEL_EXPECT=1) ===
✓ __tests__/kernel-scaffold.test.ts (10 tests) 55ms
✓ __tests__/kernel-deep-nesting.test.ts (8 tests) 67239ms
✓ every default-routed language survives a 60k-deep expression on the main thread 52801ms
✓ inside a default-sized (4 MiB) parse worker, through dist/ > defers a 60k-deep expression in every default-routed language 13050ms
✓ end-to-end: codegraph init on a repo holding the deep file > exits 0 and records deep.c alongside the normal files 936ms
Test Files 2 passed (2)
Tests 18 passed (18)
```
(The end-to-end test is what reads the Windows index back through `node:sqlite` — `files` = `deep.c`, `ok.c`; functions `add`, `foo`.)
Full `npm test` on this branch (macOS arm64, kernel staged): **190 files passed, 3,185 tests passed, 10 skipped, 0 failed.**
Clippy note: `cargo clippy` on the current toolchain (1.92) reports 18 pre-existing lints
(`manual_contains`, `unnecessary_to_owned`, …) in walker code this PR only touched by
inserting guard lines; none are in `stack.rs`/`lib.rs`. Left alone to keep the diff
reviewable.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
https://claude.ai/code/session_01LxZj6W6Y1SHXwvpT3uwJpK
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[package]
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name = "codegraph-kernel"
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version = "0.1.0"
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edition = "2021"
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license = "MIT"
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publish = false
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description = "Native extraction kernel for CodeGraph — tree-sitter parse+extract with one JS boundary crossing per file"
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[lib]
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crate-type = ["cdylib"]
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[dependencies]
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napi = { version = "3", default-features = false, features = ["napi8"] }
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napi-derive = "3"
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tree-sitter = "0.25"
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sha2 = "0.10"
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regex = "1"
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# Grammars — MUST stay revision-matched with the wasm grammars the fallback
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# path loads (tree-sitter-wasms npm package / src/extraction/wasm/). The
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# kernel-grammar-parity test asserts node-kind-table equality at test time;
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# bump these together with the wasm side or that gate fails.
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tree-sitter-typescript = "0.23"
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tree-sitter-javascript = "0.25"
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tree-sitter-java = "0.23"
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tree-sitter-python = "0.23"
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tree-sitter-go = "0.23"
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# Pinned exact: the vendored wasm (src/extraction/wasm/) was built from these
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# tags' checked-in parser.c, sha-matched against these registry tarballs
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# (R7a prep, #1345). A patch bump here without re-vendoring breaks the match.
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tree-sitter-c = "=0.24.2"
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tree-sitter-cpp = "=0.23.4"
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tree-sitter-rust = "=0.24.2"
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# csharp: the vendored wasm (#717) predates the kernel and was verified
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# table-identical to this crate's tarball (ABI 15, STATE_COUNT 8053, node-kind
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# and field tables — csharp checklist header). Bump crate + wasm together.
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tree-sitter-c-sharp = "=0.23.5"
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# ruby: content bump, ABI stays 14 (the v0.23.1 tag predates the ABI-15
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# generator) — kernel-grammar-parity asserts same-revision, not same-ABI.
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tree-sitter-ruby = "=0.23.1"
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# php: the walker calls LANGUAGE_PHP (the full HTML-interleaving variant the
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# wasm ships) — NEVER LANGUAGE_PHP_ONLY, which errors on leading HTML.
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tree-sitter-php = "=0.24.2"
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# swift: the vendored wasm is built from THIS crate's tarball src/ (the tag's
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# checked-in parser.c is an older ABI-14 generation that can never sha-match;
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# grammar.json rules are JSON-equal — swift checklist header). parser.c is
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# ~20MB generated — expect slow compiles.
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tree-sitter-swift = "=0.7.3"
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# r: the vendored wasm IS r-lib v1.2.0 and this crate's tarball ships both
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# generated artifacts sha-identical to the tag (parser.c 6221657347…,
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# scanner.c 1209d11076… — r checklist §Grammar prep). ABI 14 (the tag
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# predates the ABI-15 generator) — parity asserts same-revision, not
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# same-ABI (ruby precedent). Bump crate + wasm together.
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tree-sitter-r = "=1.2.0"
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# luau: the vendored wasm IS tree-sitter-grammars v1.2.0 and this crate's
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# tarball ships parser.c/scanner.c sha-identical to the tag (8f25bc17… /
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# a157bb52… — lua-luau checklist §Grammar prep). ABI 14. Lua itself is
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# vendored C (build.rs) — its v0.4.1 revision is not on crates.io.
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tree-sitter-luau = "=1.2.0"
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# tree-sitter-language: the version-agnostic LanguageFn shim for the vendored
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# kotlin grammar C (see build.rs — no kotlin crate dep is possible).
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tree-sitter-language = "0.1"
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# Stack-bounds queries for the walker stack guard (src/stack.rs, #1581):
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# pthread_getattr_np / pthread_get_stackaddr_np. Already in the lock file
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# transitively; Windows uses a hand-declared kernel32 extern instead.
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[target.'cfg(unix)'.dependencies]
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libc = "0.2"
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[build-dependencies]
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napi-build = "2"
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cc = "1"
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[profile.release]
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lto = true
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codegen-units = 1
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strip = "symbols"
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