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…zer on ASAN builds The RSS test for the handler structs makes 1.79 million on() and onDocument() calls. On the ASAN lane that takes 11.8 to 14.5 s of the 15 s limit on the requested instance type, and a slower machine times out on every attempt. ASAN builds now run a LeakSanitizer test for the same regression: 4096 registrations from a macrotask, then an exit with detect_leaks=1. The RSS test is unchanged on release builds and is skipped on ASAN builds.
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Updated 1:43 AM PT - Oct 1st, 2026
❌ @robobun, your commit 40ffc05 has 1 failures in
🧪 To try this PR locally: bunx bun-pr 44359That installs a local version of the PR into your bun-44359 --bun |
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info⚙️ Run configurationConfiguration used: Repository: oven-sh/bun/.coderabbit.yaml Review profile: ASSERTIVE Plan: Essentials Run ID: 📒 Files selected for processing (1)
Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 5 remain after this review. WalkthroughThe HTMLRewriter leak tests use ASAN-specific RSS-test settings and add a LeakSanitizer test for ASAN builds on non-Windows platforms. ChangesHTMLRewriter leak tests
Suggested reviewers: Priority: ⬇️ Low Merge Risk: 🔵 Low · up to The LeakSanitizer test adds a timeout contrary to test guidance. This bounded issue does not prevent merging with owner awareness or follow-up. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Review comments at @test/js/workerd/html-rewriter-leak.test.ts:
- Line 306: Remove the explicit 90_000 timeout and its associated timeout
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test/js/workerd/html-rewriter-leak.test.ts
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Status Reproduced with a release ASAN build of main (
The diff is green. Build 122270 finished with 180 of 181 jobs passed, and this file passes on the asan lane in 6.60 s (14.8 to 18.0 s before). The one red job is PR: #44359 |
…r of the count LeakSanitizer cannot see memory that something still points to at exit, so the RSS delta stays on the ASAN lane. ASAN builds run 1000 rewriters per pass in place of 4000, with a bound of 6 MB: the unfixed leak measures 11 to 14 MB there and a clean build -1.5 to 2 MB, because the quarantine is off. The LeakSanitizer test no longer asserts on a counter that the child script maintains by itself.
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LGTM — the follow-up commit addresses both points from my earlier pass (the RSS test stays on the ASAN lane with a branched N and bound, and the self-maintained counter assertion is gone).
What was reviewed:
- Traced the LeakSanitizer child's env knobs: BUN_DESTRUCT_VM_ON_EXIT is read in src/jsc/VirtualMachine.rs, test/leaksan.supp exists and carries the JSModuleLoader entries that motivate the setImmediate wrapper, and the ASAN_OPTIONS/LSAN_OPTIONS shape matches test/js/valkey/valkey-gc.test.ts and test/js/bun/shell/shell-worker-terminate-leak.test.ts.
- Checked the ASAN RSS branch: N=1000 with quarantine off keeps the fixed delta (-1.5 to 2 MB per the comment) well under the 6 MB bound and the bound under the 11-14 MB unfixed signal; quarter workload puts the ASAN run around 3 s of the 15 s ceiling.
- Confirmed withoutAsanWarning is a module-level const defined later in the file, which is safe since test bodies run after module evaluation; pipes are drained concurrently and stdout is asserted before exitCode.
Extended reasoning...
The PR touches only test/js/workerd/html-rewriter-leak.test.ts: it branches the existing RSS leak test's workload and bound on isASAN and adds a LeakSanitizer-gated sibling test for the same handler-struct leak, with no production code and no security-sensitive surface. The second commit (40ffc05) resolved both inline findings from the prior run — the ASAN lane keeps measuring RSS growth rather than dropping it, and the vacuous counter assertion was removed. The new test copies the established LSAN pattern used by several other tests in the suite, the env knobs it sets are consumed by src/, and the file has no CODEOWNER; the only outstanding third-party event is a non-blocking COMMENTED review. The hunt ran dry with no findings, so a human look is not needed beyond the usual merge flow.
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…ng the streams of a collected rewrite (#43379) ### Problem - `element.onEndTag(fn)` makes `fn` a GC root (`ProtectedJSValue` in `EndTagHandler`, `src/runtime/api/html_rewriter.rs`). If `fn` reaches the output `Response` and the rewrite stops early, 200 of 200 Responses stay. - Main also uses the streams of a collected rewrite, in four places. `cancel_from_output()` and `abandon_suspension()` close a dead JS input (`SEGV` in `JSReadStreamIntoSinkOperation::result()`, or `ASSERTION FAILED: status() == Status::Pending`). `abandon_suspension()` writes to a freed output (`heap-use-after-free` in `ByteStream::on_data`). `Bun.ModuleGraph.dispose()` cancels a stream source that is dead, or that is freed under the call (a segfault on a release build with no options). The leak hid the first. ### Fix - `onEndTag` callbacks live in a JS array in `endTagHandlers`, a new visited slot of the transform cell. The lol-html handler keeps an index. - `cancel_from_output()` cuts the output's edge to the transform cell last, as `fail()` and `finish()` already do. - The pipe's reference to its own cell is a `JsRef` instead of a bare `JSValue`, so a dead, unswept cell reads as `None`. - The two entries that nothing reachable makes, the `abandon_suspension()` task and `NewSource`'s `on_abort` (`dispose()`), hold the wrapper that they read for the call, and leave a collected one to its finalizer. - Verified: 23 new tests (`test/js/workerd/html-rewriter-leak.test.ts`, `module-graph-gc.test.ts`). 11 fail on a debug build of main, 13 on release ASAN. Other suites: Notes. Self-reviewed: 3 concerns raised, 3 addressed. ### Background - `gcProtect` makes a value a GC root, so a cycle through it is never garbage. A visited slot is an edge that the collector traces. - The transform cell (`HTMLRewriterTransform`) keeps the input stream of one `transform()` alive. The native pipe holds that stream as a raw pointer. - Considered the cell in the `PipePin` guard of every entry point (an earlier version of this PR), and a `Strong` on the input (a root per rewrite). Notes say why not. ### Downsides - `Element` grows from 40 to 48 bytes, `RewriterPipe` from 272 to 304, the release binary by 8,960 bytes. - A handler without `onEndTag()` costs the same within noise (150 ns per element, base-to-base difference up to 1.2 ns). With it, 41 to 48 ns less. - Two leaks without `onEndTag()` remain (Notes). <details><summary>Notes</summary> **Report.** There is no GitHub issue. #43210 measured the leak and left it for a follow-up, and its review asked for it: #43210 (comment). This is the last `ProtectedJSValue` in `html_rewriter.rs`. **Why a visited slot.** `REVIEW.md` ("Root or copy every JSValue held beyond the current call") asks for WriteBarrier members declared in `.classes.ts`, and keeps `protect` for a justified self-keepalive. #43210 applied that to the `handlers` slot. The third shape below also needs it: a rewrite whose input never ends reaches no terminal state, so only collection of the transform cell can free it, and a root prevents that collection. **Repro of the leak.** `MODE` is `ok`, `throw` or `cancel`. The `</div>` end tag never arrives. ```js const { heapStats } = require("bun:jsc"); let fired = 0; const fr = new FinalizationRegistry(() => fired++); const N = 200; const mode = process.env.MODE ?? "throw"; async function once() { const holder = {}; const rw = new HTMLRewriter() .on("div", { element(el) { el.onEndTag(() => holder.res); } }) .on("p", { element() { if (mode === "throw") throw new Error("boom"); } }); let ctrl; const res = rw.transform(new Response(new ReadableStream({ start(c) { ctrl = c; } }))); holder.res = res; fr.register(res, 0); const chunk = new TextEncoder().encode("<div><p>x</p>"); if (mode === "cancel") { const reader = res.body.getReader(); ctrl.enqueue(chunk); await reader.read(); await reader.cancel(); } else { ctrl.enqueue(chunk); ctrl.close(); try { await res.text(); } catch {} } } for (let i = 0; i < N; i++) await once(); for (let i = 0; i < 6; i++) { Bun.gc(true); await Bun.sleep(20); } console.log(mode, "retained", N - fired, "of", N, "protected Function", heapStats().protectedObjectTypeCounts.Function ?? 0); ``` **Measurements of the leak** (debug builds, retained Responses and protected Functions of 200, graphs of 15): | shape | main (367d939) | this PR | | --- | --- | --- | | rewrite completes | 0, 0 | 0, 0 | | a later handler throws, the body is read | 200, 200 | 0, 0 | | the output reader cancels | 200, 200 | 0, 0 | | the input never ends, all dropped, nothing pending on the output | 200, 200 | 0, 0 | | disposed `Bun.ModuleGraph` whose code left such a rewrite | 15 graphs | 1 graph | | the same graph code without `onEndTag()` (control) | 1 graph | 1 graph | Release builds of the merge base 37471e5 and of this PR give the same result for `throw` and `cancel`: 200 of 200, and 0 of 200. On main the heap snapshot of the new ModuleGraph test names the retainer: `root(ProtectedValues) Function -> JSLexicalEnvironment -> JSModuleEnvironment -> JSLexicalEnvironment -Variable:moduleGraph-> ModuleGraph`. **The dead input, case 1: `cancel_from_output()`.** An earlier version of this PR failed on the x64 ASAN lane: the new test "when the output reader is cancelled" aborted with `ASSERTION FAILED: status() == Status::Pending`. The cause is on main. `cancel_from_output()` starts with `detach_output()`, which clears the `owner` slot of the output stream. If script holds only the reader, that slot was the last GC path to the transform cell. The next step allocates the abort reason, so a collection can finish there. `detach_input_source()` then closes the sink controller of the JS input through `SourceHandle::JSController`, a raw pointer to a cell that only the transform cell kept alive. On main the protected `onEndTag` callback kept such a rewrite alive forever, so the window was closed for exactly the rewrites that the leak tests make. Main has the bug with no `onEndTag()` call. This script requests a collection before each `reader.cancel()`: ```js const encoder = new TextEncoder(); const N = 200; let cancelled = 0; for (let i = 0; i < N; i++) { let controller; const input = new ReadableStream({ start: c => void (controller = c), cancel() { cancelled++; } }); const reader = new HTMLRewriter().on("div", { element() {} }).transform(new Response(input)).body.getReader(); controller.enqueue(encoder.encode("<div><p>x</p>")); controller = undefined; if ((await reader.read()).done) throw new Error("done early"); Bun.gc(false); await reader.cancel(); } Bun.gc(true); console.log(JSON.stringify({ rewrites: N, cancelled })); ``` | release ASAN build | main | this PR | | --- | --- | --- | | plain run, 3 runs | `cancelled` is 195, 194, 200 of 200 | 200 of 200 | | `BUN_JSC_collectContinuously=1` | `SEGV on unknown address 0x000000000010` | 200 of 200 | The stack of the SEGV: `JSC::ClassInfo::isSubClassOf` < `JSReadStreamIntoSinkOperation::result()` < `Bun::WebStreams::rsisFinish` < `jsWebStreamsHandler_onReadStreamIntoSinkClose` < `JSC::runInternalMicrotask`. The failure needs a collection that finishes between `detach_output()` and the close of the input. It did not occur on a debug build or on a release build without ASAN. The regression test runs the script under `BUN_JSC_collectContinuously=1` on release builds (not on Windows, where that option is very slow), so it fails on main only on the release ASAN lanes. **The fix for case 1.** `detach_output()` moves to the end of `cancel_from_output()`, next to `release_input_roots()`. The reader that cancels then reaches the cell through the `owner` slot until the input is closed. This is the order of `fail()` and `finish()`, and the rule that the doc comment of `release_input_roots()` already states for the input's edges. Alternatives: - Keep the cell on the stack in the `PipePin` of `write`, `end_from_stream`, `resume`, `cancel_from_output` and `fail` (an earlier version of this PR). Each of those is entered by a peer whose own cell has an internal edge to the transform cell (`owner`, `sinkOwner`, the Response's `transform` slot, the context of a promise reaction). The guard mattered where the pipe itself cut that edge too early (this case), and where the first caller of the chain held nothing (cases 3 and 4). It does nothing for a cell that is already dead at the entry, so that version still crashes in case 4. It also made `EnsureStillAlive` a struct field. Everywhere else in the tree it is a local. - A `Strong` on the controller in `SourceHandle::JSController`. That is one more root per rewrite with a JS input, and a root is what made the leak. **The dead input, case 2: `abandon_suspension()`.** A review of this PR found it. It is on main too. A handler returns a promise that never settles, and script drops everything. The collector then frees the promise, and the destructor of its native context queues `abandon_suspension`. That task asked `cell.is_cell()` to learn if the transform cell is alive. The pipe's `cell` field was a bare `JSValue` that the cell's finalizer clears, and the finalizer runs at the sweep. A cell that is dead but not swept yet still passes `is_cell()`, so the task called `fail()`, and `fail()` closed the dead sink controller. That field is a hand-written weak reference. `JsRef` is the one the rest of the runtime uses for a native object's own wrapper (the stream sources next to this pipe do), and since #39334 its `try_get()` gives `None` for a dead, unswept cell, which is the answer of `JSC::Weak::get()`. The field is now a `JsCell<JsRef>`, and every read of it goes through `try_get()`. The task clears the input and output handles without a call into them when that is `None`, as it already did for a swept cell. ```js const N = 50; const encoder = new TextEncoder(); const tick = () => new Promise(resolve => setImmediate(resolve)); let cancelled = 0; for (let i = 0; i < N; i++) { let controller; const input = new ReadableStream({ start: c => void (controller = c), cancel: () => void cancelled++ }); new HTMLRewriter().on("p", { element: () => new Promise(() => {}) }).transform(new Response(input)); controller.enqueue(encoder.encode("<p>x</p>")); } for (let i = 0; i < 5; i++) await tick(); for (let round = 0; round < 10; round++) { Bun.gc(false); const junk = []; for (let j = 0; j < 500; j++) junk.push({ j }); await tick(); } process.stdout.write(JSON.stringify({ rewrites: N, cancelled })); ``` Run it as a file. A release build of main exits with `panic(main thread): Segmentation fault at address 0x0` in 10 of 10 runs. A debug build of main stops at `ASSERTION FAILED: decontaminate()`. A release ASAN build of main reports the same `SEGV` as case 1, with this stack: `JSReadStreamIntoSinkOperation::result()` < `rsisFinish` < `pumpOnClose` < `sinkControllerOnClose` < `SourceHandle::cancel` < `RewriterPipe::fail` < `RewriterPipe::abandon_suspension`. This PR prints `{"rewrites":50,"cancelled":0}` on all three builds. Bun 1.4.2 does not crash on this script. #37108 fixed the opposite direction, a controller destructor that reached a freed pipe. **The freed output, case 3: `abandon_suspension()` again.** It is on main too. The handler's promise is collected while script still holds the `Response`, so the task is queued for a reachable rewrite. Script drops the `Response` before the task runs. The cell is then unreachable, but no collection has found that out, so it reads as alive. `fail()` allocates (the error, the abort of the input), and a collection in there sweeps the cell and both streams. `fail()` then writes the error through `output`, a raw pointer to the freed `ByteStream`. This entry is a task that a destructor queued, so nothing on its stack reaches the cell. It keeps the cell that it read in a local `EnsureStillAlive` until it returns. ```js const encoder = new TextEncoder(); const tick = () => new Promise(resolve => setImmediate(resolve)); const responses = [], promises = []; function start() { let controller; const input = new ReadableStream({ start: c => void (controller = c) }); const response = new HTMLRewriter() .on("p", { element() { const p = new Promise(() => {}); promises.push(p); return p; } }) .transform(new Response(input)); response.body; responses.push(response); controller.enqueue(encoder.encode("<p>x</p>")); } for (let round = 0; round < 20; round++) { for (let i = 0; i < 4; i++) start(); await tick(); promises.length = 0; Bun.gc(true); responses.length = 0; await tick(); } ``` With `BUN_JSC_slowPathAllocsBetweenGCs=25` (a full collection at every 25th slow-path allocation) a release ASAN build of main reports the `heap-use-after-free` in 10 of 10 runs, and also for each of 7, 13, 20, 33, 50, 64, 80, 100 and 150. This PR exits with 0. A debug build and a release build without ASAN of main do not report it. **The dead or freed source, case 4: `Bun.ModuleGraph.dispose()`.** It is on main too, and needs no `onEndTag()`. `dispose()` cancels the source of every stream that the graph's script was given (`NewSource`'s `on_abort`, #42590), from native code. The JS wrapper owns the source, and nothing on that stack reaches a wrapper that script has dropped. `AbortHandleOwner` has a `KeepAlive` type for what keeps the owner alive while `on_abort` runs. `NewSource` declared none. - A collection that finishes inside `cancel()` frees the source under the call, together with the rewrite that feeds it. - After a collection that finished before, the wrapper is dead and waits for its sweep. `cancel()` then tells the rewrite, which closes its dead input. `NewSource` now keeps its wrapper (`this_jsvalue.try_get()`) alive for the call. For a wrapper that is collected and not swept yet it does nothing: the peers are collected too, and the finalizer releases the source. A source whose wrapper is finalized while native refs remain (a child's pipe that nobody reads) is cancelled as before. ```js const TICKS = 0; // or 1 const encoder = new TextEncoder(); const tick = () => new Promise(resolve => setImmediate(resolve)); const rewrite = input => new HTMLRewriter().on("div", { element() {} }).transform(input); function start(chained) { for (let i = 0; i < 20; i++) { const input = new ReadableStream({ start: c => void c.enqueue(encoder.encode("<div>x")), cancel() {} }); const output = rewrite(new Response(input)); (chained ? rewrite(output) : output).body; } } for (const chained of [false, true]) { for (let i = 0; i < 20; i++) { const graph = new Bun.ModuleGraph(); graph.run(() => start(chained)); await tick(); Bun.gc(false); for (let t = 0; t < TICKS; t++) await tick(); graph.dispose(); } } ``` Run it as a file, with no options. 5 runs for each value of `TICKS`: | build | `TICKS = 0` | `TICKS = 1` | | --- | --- | --- | | main, release | segfault, 5 of 5 | segfault or abort, 5 of 5 | | main, debug | `ASSERTION FAILED: decontaminate()`, 5 of 5 | the same, 5 of 5 | | main, release ASAN | `decontaminate()` or `SEGV`, 5 of 5 | `SEGV`, 5 of 5 | | the version of this PR with the cell in `PipePin`, release ASAN | `ASSERTION FAILED: result`, 5 of 5 | `SEGV` or `decontaminate()`, 5 of 5 | | this PR, release ASAN | passes, 5 of 5 | passes, 5 of 5 | **Each of the changes is needed.** Release ASAN builds, the repros of cases 1 to 3: | build | case 1 (`slowPathAllocsBetweenGCs=1`, 10 rewrites) | case 2 | case 3 | | --- | --- | --- | --- | | main | `cancelled` is 0 of 10 | `SEGV` | `heap-use-after-free` | | this PR with only the `JsRef` | `cancelled` is 0 of 10 | passes | `heap-use-after-free` | | this PR | 10 of 10 | passes | passes | **Why `Element` has a back reference.** `on()` handlers find their list through the pipe whose lol-html call is on the stack. `onEndTag()` cannot: after an `await` in an async handler no lol-html call is on the stack, and inside a handler of a nested, synchronous rewrite the pipe on the stack is the inner one. Both cases work on main and have a test here. `handler_callback` gives the pipe to the wrapper when it makes it. `Element::invalidate()` clears it together with the lol-html pointer. That happens when the handler returns, or when the pipe drops the wrapper it parked, so the reference never outlives the pipe. **Replacement.** A second `onEndTag()` on the same element replaces the first callback, in one handler or across two `on()` handlers. That is the behavior of main (`handlers.clear()` then push). lol-html gives every matching handler the same `Element`, and a suspension moves the user data with the parked copy. So the first call pushes the one lol-html handler and records its slot as the element's user data, and a later call only stores the new callback into that slot. **A parked element that outlives its transform cell.** A handler returns a promise, the element is parked, then the promise and the cell are collected together. Until the queued `abandon_suspension` task runs, script can still call `onEndTag()` on the parked element. The cell is then swept, or dead and not swept yet. In both states `try_get()` is `None`, and `hold_end_tag_callback` stores nothing. It also stores nothing for a parked element whose rewrite was cancelled or failed. In all of these the end tag can never come. The last test in the file covers the collected case. **Return value.** Unchanged: the element while it is attached, `null` once it is detached. **Sizes.** `size_of` in the release profile, merge base then this PR: `Element` 40, 48 (one per element handler call, freed when the handler returns). `RewriterPipe` 272, 304 (one per `transform()`, alignment 16). `EndTagHandler` 24, 16. The transform cell gets one more `WriteBarrier` (8 bytes). The first `onEndTag()` call on an element now boxes a 4-byte index as the lol-html user data, and no longer adds an entry to the VM's table of protected values. `size` of the linux-x64 release binaries: text 80,681,674, then 80,690,634. Data and bss do not change. **Speed.** Release builds of the merge base and of this PR, linux-x64, pinned to one core. One process rewrites a document of 20,000 elements with one element handler, and reports the best of 40 runs in nanoseconds per element. 25 rounds run the processes in turn: base, PR, base again. The table gives the minimum of the rounds, and the median in parentheses. The third column is the same base binary, which shows the noise. | case | base | this PR | base again | | --- | --- | --- | --- | | `<p>x</p>` x 20,000, handler only | 150.1 (154.9) | 150.9 (155.7) | 151.3 (157.7) | | `<p>x</p>` x 20,000, handler calls `onEndTag()` | 298.3 (306.2) | 257.6 (266.8) | 298.0 (306.7) | | `<div>` nested 50 deep x 400, handler only | 150.1 (154.2) | 150.5 (154.4) | 150.1 (154.5) | | `<div>` nested 50 deep x 400, handler calls `onEndTag()` | 322.1 (331.4) | 274.6 (280.6) | 326.8 (332.7) | `try_get()` is one call into C++ per handler call. The version of this PR without it measured 151.0, 259.8, 151.9 and 273.8 in the same rounds. **Not changed.** Each of these keeps a rewrite alive on main and on this PR with no `onEndTag()` call at all (100 rewrites each): - A failed rewrite keeps the handler's error in the output body as a `Strong` until the body is read (`fail()`). If that error references the output `Response` (for example `error.response = res`) and nothing reads the body, 100 of 100 Responses stay. With the body read, 0 stay. An error that does not reference the Response retains nothing. - A `read()` that is pending on the output while the JS input stream can never produce again keeps 100 of 100 Responses, through the protected promise and buffer of the pending pull. A pending `.text()` leaves 100 protected Promises (`promise_value.protect()`, `src/runtime/webcore/Body.rs:453`). - A rewrite that fails or is cancelled keeps its lol-html rewriter (the parser arena) until the transform cell is collected. Only `finish()` frees it earlier. A parked wrapper can still point into it, so an earlier free needs its own change. **Tests.** 23 new tests. On a debug build of main 11 fail: the three leak shapes, four of the five kept-Response shapes, the parked rewrite that dies with its handler promise, the two `dispose()` tests of case 4, and the ModuleGraph test. On a release ASAN build of main the cancel test under continuous collection and the test of case 3 fail too. The other tests guard the new storage and pass before the fix: the callback stays alive until its end tag with nothing else referencing it (GC churn in between, half of the outputs dropped), slot reuse under nesting, one end tag that closes several elements, callbacks that run after a handler cancelled the output earlier in the same chunk, replacement (one handler, two handlers, across a suspension), `onEndTag()` after an `await`, an outer element used in a nested rewrite, an indexed accessor on `Array.prototype`, the parked element whose rewrite was collected, and the kept-Response case of a rewrite that completes. **Suites run on the debug (ASAN) build:** `test/js/workerd/html-rewriter-leak.test.ts` (49 pass, 1 skipped in debug), `test/js/bun/module-graph/module-graph-gc.test.ts` (33 pass), `test/js/workerd/html-rewriter.test.js` (186 pass), `test/js/workerd/html-rewriter-end-error.test.ts`, `test/js/web/html/html-rewriter-doctype.test.ts`, `test/regression/issue/htmlrewriter-additional-bugs.test.ts`, `test/regression/issue/text-chunk-null-access.test.ts`, `test/js/bun/http/serve-stream-body-error.test.ts`, and the HTMLRewriter cases of `test/js/web/workers/worker-terminate-lifetime.test.ts` and `test/js/bun/module-graph/module-graph-isolation.test.ts`. On the release ASAN build: the leak file with the CI environment of the ASAN lane (`BUN_JSC_validateExceptionChecks=1`, `BUN_GARBAGE_COLLECTOR_LEVEL=1`) and `html-rewriter.test.js`, 3 runs. Also run by hand, on the earlier version with the cell in `PipePin`: a nested document with `Bun.gc(true)` in handlers and callbacks under `BUN_JSC_collectContinuously=1`, and `terminate()` of workers that hold pending callbacks in each state. **A test of this file that is slow on main.** "HTMLRewriter does not leak element/document handler allocations" passes 15 s on a loaded release ASAN build, on main and on this PR. #44359 and #44377 change that test. **Self-review.** The review of the first commit asked for the ModuleGraph test, for the narrower wording of the measured shapes, and for the "Not changed" list. All three are in. </details> <!-- robobun:evidence:begin --> --- **no test proof** · iteration 0 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/bun/module-graph/module-graph-gc.test.ts <!-- robobun:evidence:end --> --------- Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
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Problem
test/js/workerd/html-rewriter-leak.test.tsis red on debian 13 x64-asan (build 122042, 4 of 4).HTMLRewriter does not leak element/document handler allocationsreportsthis test timed out after 15000ms, thenJSON Parse error: Unexpected EOF.on()andonDocument()calls. On the ASAN lane that takes 11.8 to 14.5 s of the 15 s limit on the requestedr7i.2xlarge, so a slower machine fails every attempt.Fix
N4000 to 1000) with a 6 MB bound. On the lane the test takes about 3.2 s (build 122270).180224 byte(s) leaked in 4096 allocation(s).bun bd test test/js/workerd/html-rewriter-leak.test.ts, a release ASAN build with the CI environment, a release build.Background
on()andonDocument()each allocate one handler struct. Fix HTMLRewriter handler allocation leak in LOLHTMLContext.deinit #29879 fixed a leak of them, and this test guards it.test/leaksan.supphides allocations made during module evaluation. So that child registers fromsetImmediate, liketest/js/valkey/valkey-gc.test.ts.Notes
The failure on the lane. Builds 121960 to 122095 (2026-09-30 20:11 to 2026-10-01 00:30 UTC), the asan shard that runs this file, by the
free -mtotal of the agent (#38042 matched the totals to instance types):free -mtotalr7i.2xlarge(requested)r7a.2xlarger6i.2xlargeBuilds 120727 and 121375 are 4 of 4 timeouts on 63270 machines, so the requested type also fails.
On the 107 clean runs the dot of this test appears 12.59 to 15.33 s after the file starts (median 13.39 s, p90 14.87 s). In the failed runs the timeout message appears 15.73 to 15.93 s after the file starts, so the test starts about 0.8 s in. That gives 11.8 to 14.5 s for the test.
The cost did not change.
test/expected-durations.jsonhas 11.3 s for this file on the asan lane on 2026-07-07 and 2026-07-19, when the file had two tests and this one ran six passes. That is about 1.8 s for each pass of 256,000 registrations. Seven passes take 12.6 s now.Why the lane is slow. The lane is a release build with ASAN and assertions. The runner also gives this file
BUN_JSC_validateExceptionChecks=1,detect_leaks=1andBUN_DESTRUCT_VM_ON_EXIT=1, and the child inherits them. A release ASAN build of main (bun run build:asan, 2f1d7f6) in this container takes 1.0 s for each pass without those variables and 1.65 s with them. A release build takes 0.1 s. The cost is spread over the whole call (three or four property reads, the handler list, the selector parse, the box). No single part dominates.Reproduction. Release ASAN build of main, environment of the lane. The RSS test of main took 12.4 s, 12.9 s and 14.6 s of its 15 s, and timed out once, with no extra load. Pinned to 4 CPUs that 4 busy loops share, it fails with
this test timed out after 15000ms(2 of 2). Run in turns with main, this branch took 4.0 s and 3.2 s where main took over 15 s and 14.6 s.The ASAN numbers. All on the release ASAN build with the environment of the lane, quarantine off as the test sets it.
NThe scratch build for "with the leak" adds a
DropforLOLHTMLContextthat callsmem::forgeton each handler box. That is the leak #29879 fixed. The clean deltas come in steps of about 1 MB, and the count does not change them. So a smaller count moves the signal toward that floor. At 1000 the bound is 3 times the largest clean delta and about half the smallest leak delta.Time for the child at
N1000 in this container: median 4.1 s in 100 direct runs (3.6 to 4.4 s for 90 of them), and 3.0 to 5.8 s in 40 runs through the test file. On the lane, build 122270 ran this change on a 63270 machine: the file took 6.60 s (14.8 to 18.0 s before), and the dot of the RSS test appears 3.90 s after the file starts. That is about 3.2 s for the test, so about 7 s on the slowest machine type seen (2.1 times slower).With the leak and the environment of the lane, the RSS child can also run into the 15 s limit: LeakSanitizer symbolizes 448,000 stacks at exit before the suppressions hide them. The test fails either way. main behaves the same.
The LeakSanitizer test.
180224 byte(s) leaked in 4096 allocation(s), exit code 134The report names
HTMLRewriter::on_andHTMLRewriter::on_document_. The same child at the top level of the module exits 0 with the leak: theJSC::JSModuleLoader::evaluateNonVirtualentry ofleaksan.supphides all of it. That is why the child usessetImmediate. The child prints the count of liveHTMLRewritercells after the last collection, and the test wants fewer than a quarter of the 64 it made (it sees 1 to 3).It adds two things to the RSS test. It is exact, so a leak of a few bytes for each rewriter fails. And it runs on debug builds, where the RSS test is skipped, so
bun bd testnow covers this regression.The 90 s limit of the LeakSanitizer test. A pass takes 0.2 to 1.7 s on the release ASAN build and 1.6 to 5.1 s on a debug build in this container. A failure takes 6.1 to 23.7 s because LeakSanitizer symbolizes the report.
test/js/bun/shell/shell-worker-terminate-leak.test.tsuses the same limit for the same reason.History of this PR. The first commit skipped the RSS test on ASAN builds and relied on LeakSanitizer there. Review pointed out that LeakSanitizer cannot see memory that something still points to. The second commit keeps the RSS test on ASAN at a quarter of the count. Build 122245 ran the first commit: the file took 3.38 s on the asan lane.
CI. In builds 122245 and 122270 the one red job is
test/js/bun/spawn/spawn.test.tson the asan lane (stdout reader of an unref'd child and process lifetime). This PR does not touch it, and it is red in build 122042 too. It is reported separately.Found on the way, not in this PR. The RSS test on release builds: with the leak put back, a release build of main measures 33 to 37 MB (12 runs) against the bound of 35. #43210 made the handler structs smaller: 64 and 80 bytes before (from the field types), 40 and 48 bytes now (from the LeakSanitizer report). So the unfixed delta fell from about 55 MB to about 35 MB. This is reported separately.
no test proof · iteration 0 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/workerd/html-rewriter-leak.test.ts