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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.
…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.
…on release builds On release builds the resident memory test for the handler structs of on() and onDocument() could pass with the leak. With the leak of #29879 put back, a release build measures 33 to 36 MB against the bound of 35 MB, and the test passes 5 of 12 runs. Since #43210 both structs fit a 48-byte block. Release builds now read mimalloc's count of live blocks (heapStats().mimalloc.malloc_bins). A round makes 1000 rewriters with 64 registrations each. The test checks that the count rises by at least one block for each registration while the rewriters are alive, and that it is back after they are collected. With the leak, the count stays 127,400 to 128,000 above the baseline, against a bound of 32,000. Without it, it ends -600 to 40 from the baseline. The resident memory test now runs on ASAN builds only. Their allocator is ASAN's, and mimalloc counts none of these structs there.
…ane (temporary) Prints the block counts and the resident memory of the handler leak workload on every release lane, to check the bounds against the platforms that only CI runs. This commit is removed before the pull request leaves draft.
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Build 122356 printed the block counts and the resident memory of every release lane. The numbers are in the pull request.
robobun
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October 1, 2026 13:16
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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; 3 remain after this review. WalkthroughThe test suite adds allocator live-block and LeakSanitizer checks for HTML rewriter handlers. It also restricts the RSS leak test to ASAN non-debug builds, reduces its workload, and lowers its RSS growth threshold. ChangesHTML Rewriter leak checks
Suggested reviewers: Priority: ⬇️ Low Merge Risk: 🔵 Low · up to The leak checks have no established functional blocker, but the new LeakSanitizer timeout still violates the repository’s test policy. Remove it or obtain an explicit policy exception; the remaining merge risk is bounded. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Review comments at @test/js/workerd/html-rewriter-leak.test.ts:
- Line 389: Remove the explicit 90_000 timeout argument and its associated
justification from the test declaration containing it, leaving the test body and
remaining arguments unchanged.
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test/js/workerd/html-rewriter-leak.test.ts
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Beyond the inline finding, I also checked that the knobs the new tests depend on are real: heapStats().mimalloc is emitted unconditionally from mi_stats_get_json in src/jsc/modules/BunJSCModule.h (not behind the malloc-debugging ifdef), and BUN_GARBAGE_COLLECTOR_LEVEL / BUN_DESTRUCT_VM_ON_EXIT are both read in src/jsc/VirtualMachine.rs. The three subprocess tests drain stdout/stderr/exited concurrently and use await using, so the harness conventions hold.
Extended reasoning...
The PR only touches test/js/workerd/html-rewriter-leak.test.ts, splitting one RSS-based leak regression test into a release-lane mimalloc block-count test, an ASAN-only RSS test with a tighter bound, and an ASAN LeakSanitizer test; it touches no security-sensitive surface. The confirmed inline finding about the held-before guard being satisfiable by non-handler blocks is what keeps this from being an approve.
The sum over every size class let the guard pass on the blocks of the selectors alone: about 100,000 of the 164,000 blocks of a round are not handler structs. The count is now the 48-byte class, where mimalloc puts both structs. It is up by 64,002 while the 1000 rewriters of a round are alive. One kind of struct alone gives 32,002, so the guard is 48,000. With the leak, the count stays up by 128,003 after two rounds. Without it, the count ends within 100 of the baseline.
… rewriter Without the JIT the count of the class is exact: 64,000 above the baseline while the rewriters of a round are alive and 0 after two rounds, in each of 200 runs. With the JIT it ends -62 to 66 from the baseline. The child now runs without the JIT, and the bound is 1000 blocks where it was 32,000. One leaked struct for each rewriter would be 2,000 blocks after two rounds. The test is now a concurrent test.
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Oct 3, 2026
…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
HTMLRewriter does not leak element/document handler allocations(test/js/workerd/html-rewriter-leak.test.ts) passes 5 of 12 runs with the leak of Fix HTMLRewriter handler allocation leak in LOLHTMLContext.deinit #29879 put back: an RSS delta of 33 to 36 MB againsttoBeLessThan(35).Fix
heapStats().mimalloc.malloc_bins), not RSS. It holds both structs and little else. ASAN builds keep the RSS test of test(HTMLRewriter): shrink the handler leak test on ASAN builds and add a LeakSanitizer check #44359: mimalloc counts nothing there.Background
on()andonDocument()each box one handler struct, and the rewriter's finalizer frees it.Notes
The leak for the measurements. A scratch
DropforLOLHTMLContextthat callsmem::forgeton each handler box. That is the leak of #29879. It is in no commit.Linux x64, release builds (
bun run build:release). The RSS rows are from main at 4b02e10. The other rows are from this branch, with the final test.N4000, 3 measured passes)Expected: < 1000,Received: 128000What is in the 48-byte class.
ElementHandleris 40 bytes andDocumentHandleris 48. mimalloc serves both from its 48-byte class. The class has 120 to 1,478 live blocks before the measured rounds. With 1000 rewriters alive (clean build, above the baseline):on()onDocument()The other blocks of a registration are in other classes. With both kinds registered, 1000 rewriters also hold about 65,040 blocks of 8 bytes, 33,005 of 80 bytes, and 1,003 each of 256 and 512 bytes. Most of them belong to the selector that each
on()parses.Why the child runs without the JIT. With the JIT on, the same child ends -62 to 66 from the baseline (400 runs, most of them at 3). With
BUN_JSC_useJIT=0it ends at 0 in 200 of 200 runs. The leak is native, so the JIT adds nothing to the test.test/js/node/zlib/leak.test.tsdoes the same.Every release lane. Build 122356 ran a temporary test (commit 4996388, removed in 20b7327) that printed the counts of each lane by size class, one run for each lane, with the JIT on. The second column is the 48-byte class with 1000 rewriters alive. After the rewriters were collected, the class was within 20 of its baseline on every lane. The last column is what the RSS test of main asserts on (pass 7 minus pass 4), 4 runs on each lane.
The assertions are
alive > 48000andafter two rounds < 1000.ASAN builds. The structs come from ASAN's allocator there. On a debug ASAN build the count of the class is 0, and it stays 0 while 50 rewriters are alive. So the first assertion fails there, and ASAN builds keep the RSS test with the numbers of #44359 (
N1000, bound 6 MB) and its LeakSanitizer test. Only the conditions that selected those numbers for ASAN builds are gone. An exact count on ASAN builds needs a binding that main does not have (#41207 proposes one).History of this PR. The first version summed every size class and required
alive >= 64,000. Review pointed out that the blocks of the selectors alone satisfy that: a round holds about 164,000 blocks, and about 100,000 of them are not handler structs. The count is now the class of the structs. Review then pointed out that the bound of a quarter of the leak (32,000) let a leak of up to 15 structs for each rewriter pass. The bound is now 1000. One leaked struct for each rewriter would be 2,000 after the two rounds. That case is arithmetic: no build measured it. The sum over every class ended -541 to 126 from its baseline on the ten lanes. It was below zero on some lanes because the 16384-byte class reports a negative live count there (-745 to -858 after three rounds on x64 Linux and on macOS). No block of a rewriter is in that class. It looks like the statistics lag that #34739 (open) describes.Not changed here. Review also asked for
test.concurrenton the three tests. The new test has it. The RSS test and the LeakSanitizer test run on the ASAN lane only, and their timing there is the subject of #44359, so this PR leaves them serial.Time. The new test takes 0.14 to 0.22 s on Linux x64. Ten passes of the RSS workload took 0.7 to 1.7 s on the lanes (4.1 s once on macOS aarch64), and the RSS test ran 7. The whole file takes about 1 s on Linux x64.
The other designs, in numbers.
Bun.gc(true)now hands freed memory back before it returns. A bound of about 17 MB separates 1 MB from 35 MB today. It keeps the RSS delta tied to the struct size with no check of that tie, which is how this test lost its signal without a failure. The new test has the same tie to the size class, and its first assertion checks it on each run.process.resourceUsage().maxRSSof a spawned child starts at the peak of its parent. Each child of one test run reported the same 41,840 KB, above its own RSS, so growth below that does not show.Debug builds. They skip the new test, as they skip the RSS test. A registration takes about 125 µs on a debug ASAN build, against under 1 µs on a release build. The LeakSanitizer test of #44359 runs there.
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