cron: stop the next() walk at the end of the Date range - #42297
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CronExpression::next() converts each candidate day to a calendar date through JSC. JSC converts no time value more than one day past 8.64e15. A debug build asserts in PlainGregorianDateTime when the walk reaches year 275761. Newer WebKit returns an all-zero date, so the year went back to 0, the 8-year bound never tripped, and the walk never stopped. Return None once the candidate day is past +275760-09-13. Every zone is within a day of UTC, so no later wall-clock day holds a representable instant. Also return None for a from_ms outside the Date range: the scheduler passes the clock, and fake timers can set it to any number.
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Status: merged in f385d9a. Reproduction
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Included review availability: Your plan provides up to 10 included reviews per hour; 0 remain after this review. WalkthroughThe cron parser now stops at invalid or unsupported ECMAScript Date timestamps. The API behavior and tests cover Date boundaries, time zones, impossible dates, performance, and scheduler behavior. ChangesCron Date Range Handling
Priority: ➖ Normal Merge Risk: ⚪ Minimal · up to The added child-process assertions verify normal completion, with no remaining merge-blocking risk identified. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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In `@src/runtime/api/cron_parser.rs`:
- Line 263: Update CronExpression::next around resolve_local_match so resolved
instants greater than MAX_ECMASCRIPT_TIME are rejected and the search continues
instead of returning them. Preserve normal results within the limit, and return
None once the final permitted day is exhausted.
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src/runtime/api/cron_parser.rstest/js/bun/cron/cron-parse.test.ts
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A candidate on the last day of the range can resolve past 8.64e15 in local time. next() returned it, and the scheduler armed a timer for it. Skip such a candidate and continue to the end of that day. The clamp in cron_parse is then redundant.
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LGTM — focused bound on the day-walk with a matching input-range guard, both derived from the existing MAX_ECMASCRIPT_TIME constant.
What was reviewed:
- The
from_msguard covers NaN/±Infinity/out-of-range and mirrors the existing check atsrc/runtime/api/cron.rs:1877;LAST_DAY_NOON_MSis derived, not a magic literal, and stays within JSC's ±1-day conversion window soms_to_gregorian_date_time_utc(noon_ms)is always in range. - Confirmed
resolve_local_match's 121-minute probe pastfrom_ms(now ≤ 8.64e15) also stays inside that window, so no sibling conversion site is left unbounded. - Tests follow harness conventions (spawn with
bunExe()/bunEnv, concurrent pipe drain, combined{ out, stderr, exitCode }assertion);exitCode: 0in the stricttoEqualdoubles as the "exited on its own, not SIGKILL'd" assertion for the hang guard.
Extended reasoning...
Overview
The PR adds two guards to CronExpression::next() in src/runtime/api/cron_parser.rs: an entry check that returns None when from_ms is NaN or |from_ms| > MAX_ECMASCRIPT_TIME, and a per-iteration check that returns None when the candidate day's UTC noon exceeds LAST_DAY_NOON_MS (8.64e15 + 12h). It introduces one derived constant, updates the doc comment, and adds a describe block with two spawned-subprocess tests plus a warmup call before the pre-existing timed Feb-30 assertion. Net Rust change is ~15 lines.
Security risks
None. This is a bounds check on a scheduler's day-walk over f64 time values. No parsing of untrusted structured input, no auth/crypto/permissions surface, no allocation sizing. The change strictly narrows the input space that reaches JSC's date-conversion FFI, which is a hardening in the direction of failing closed.
Level of scrutiny
Low-to-moderate. The fix is small, mechanical, and reuses an existing repo constant (bun_jsc::wtf::MAX_ECMASCRIPT_TIME, static-asserted against WTF's value in wtf-bindings.cpp). The entry guard is byte-identical in shape to the one already at src/runtime/api/cron.rs:1877. The noon_ms > LAST_DAY_NOON_MS bound is the only new reasoning, and it is sound: 8.64e15 is +275760-09-13T00:00:00Z, every real zone offset is < 24h, so no instant on a wall-clock day later than +275760-09-13 can map to a UTC instant ≤ 8.64e15. The bound is inclusive of the last day's noon itself, which is within JSC's documented ±1-day conversion margin, so the subsequent ms_to_gregorian_date_time_utc call is always valid. I also traced resolve_local_match (the only other conversion site reached from a bounded from_ms) — its probe window is from_ms + 121 min, well inside the margin.
Other factors
No CODEOWNERS entry covers src/runtime/api/ or the test path. The hunt exited on dry_streak with zero findings. Tests are added to the existing module test file, spawn with bunExe()/spread bunEnv, drain pipes concurrently, and assert a combined object with output before exit code. The describe is intentionally non-concurrent (PR states bun:test only reaps children of timed-out serial tests), which satisfies REVIEW.md's "staying serial needs a stated reason". The timeout/killSignal on Bun.spawn is a subprocess hang guard, not a jest per-test timeout; asserting exitCode: 0 in the strict toEqual fails if the child was SIGKILL'd, covering the "exited on its own" requirement. The warmup call before the timed Feb-30 test is a targeted fix to keep an existing timed assertion honest under debug+ASAN, with a comment explaining why.
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Both review findings are addressed.
All threads are resolved. |
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The optional nit from the last review is applied in 260fb80: both hang-guard tests now assert |
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LGTM — the signalCode: null assertion is now in both hang-guard tests, thanks.
What was reviewed:
LAST_DAY_NOON_MSbound: 8.64e15 + 12h is inside JSC'smaxECMAScriptTime + msPerDayconversion window on both WebKit versions, and the check runs beforems_to_gregorian_date_time_utc; the forwardgregorian_date_time_to_ms_utccall for day 14 is pure arithmetic, so no assert there.resolve_local_matchprobe path: capped atfrom_ms + 121 min(still year 275760), and anyr > MAX_ECMASCRIPT_TIMEor NaN result is filtered at the newr <= MAX_ECMASCRIPT_TIMEgate — the removed clamp incron_parseis indeed redundant.- Tests:
bunEnvspread with pinnedTZ, concurrent pipe drain,signalCode: nullon both spawns, warm-up call moves the ~150ms date-cache init outside the timed window.
Extended reasoning...
Overview
This PR bounds CronExpression::next()'s day-by-day walk at the ECMAScript Date range boundary (+275760-09-13). Three guards are added in src/runtime/api/cron_parser.rs: an up-front NaN/range check on from_ms (so a mocked scheduler clock past the range short-circuits), a noon_ms > LAST_DAY_NOON_MS check before the JSC ms→date conversion (which asserts on current WebKit debug and returns year 0 on newer WebKit, causing an infinite walk), and a r <= MAX_ECMASCRIPT_TIME filter on resolved matches. src/runtime/api/cron.rs drops the now-redundant post-next() clamp. Two subprocess hang-guard tests exercise the boundary across four time zones (including UTC+14 and UTC−4), and a warm-up call is added before the existing timed Feb-30 assertion.
Security risks
None. This is date-range boundary handling in a scheduling helper — no auth, crypto, network, or filesystem surface. The change turns a debug-assert / infinite-loop into a None return, strictly narrowing failure modes.
Level of scrutiny
Moderate. The reasoning about JSC's conversion window is subtle, so I traced each conversion call site: ms_to_gregorian_date_time_utc is now only called with noon_ms ≤ 8.64e15 + 12h, inside both the old assert bound (year ≤ maxYear) and the new canNarrowToInt64Milliseconds bound (≤ maxECMAScriptTime + msPerDay). The forward gregorian_date_time_to_ms_utc call that produces noon_ms for day 14 is arithmetic-only (dateToDaysFrom1970), so it cannot assert. resolve_local_match's probe loop stays within from_ms + 121 min, well inside the safe window, and its NaN/over-range results are caught by the new <= MAX_ECMASCRIPT_TIME filter (NaN ≤ x is false). The removed > MAX_ECMASCRIPT_TIME check in cron_parse is provably dead now that next() never returns a value outside the range.
Other factors
The bug hunt ran to dry_streak with no findings. My only prior comment (assert signalCode: null in hang-guard tests) was addressed in the latest commit — both new tests now include it in the asserted object. Tests follow harness conventions ({...bunEnv, TZ: "UTC"}, Promise.all on stdout/stderr/exited, combined-object .toEqual, 20s subprocess kill switch rather than a per-test timeout). The Pacific/Kiritimati row (0 14 13 9 * → 8.64e15) proves the bound doesn't cut off the last representable minute in the most-positive offset, and the negative-offset row proves the r <= MAX_ECMASCRIPT_TIME filter catches over-range resolutions. No CODEOWNERS entry covers these paths, and there are no outstanding CHANGES_REQUESTED reviews.
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Updated 4:25 AM PT - Sep 11th, 2026
✅ @robobun, your commit 260fb808ba9b9081686e87637cba8f846156034b passed in 🧪 To try this PR locally: bunx bun-pr 42297That installs a local version of the PR into your bun-42297 --bun |
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#42319 merged without this PR.
The branch merges into The 13 calls
Each call ran in a fresh process with a kill timer (8 s on the release builds, 60 s on the debug build). |
2 participants
Problem
CronExpression::next()(src/runtime/api/cron_parser.rs:250) converts each candidate day to a calendar date through JSC. Nothing stops the walk at the end of the Date range. JSC converts nothing more than one day past it.mainaborted:Bun.cron.parse("0 0 1 1 *", 8.64e15)gaveASSERTION FAILED: year >= minYear && year <= maxYearatPlainGregorianDateTime.h(91). A release build returnednull.mainto a WebKit where the conversion returns an all-zero date. The year goes back to 0, the 8-year bound never trips, andBun.cron.parse("0 0 30 2 *", new Date(8.64e15 - 86400000 * 400))never returns.mainand the canary hang on this call today.Fix
next()returnsNonewhen the candidate day is past +275760-09-13. Every zone offset is smaller than one day, so no instant on a later wall-clock day fits in a Date.next()also returnsNonefor afromoutside the Date range (fake timers can set the scheduler's clock to any number). It skips a candidate that resolves past 8.64e15, socron_parseneeds no clamp.test/js/bun/cron/cron-parse.test.ts. The 2 new tests fail without the fix and pass with it, onmainbefore and after Upgrade WebKit to cf1b36ec8703 #42319 (6b394bf and 158ff6c). Also ran the rest oftest/js/bun/cron/.Background
next()walks wall-clock time forward fromfrom, day by day, until all five fields match.Dateholds.mainhas the endless loop until this PR merges.Notes
Upstream change. WebKit 320788@main (d5ba0ecec9, bug 323443) changed
DateCache::computeGregorianDateTimeinJSDateMath.cppfromif (!std::isfinite(ms)) return { };toif (!canNarrowToInt64Milliseconds(ms)) return { };, wherecanNarrowToInt64Milliseconds(ms)isisfinite(ms) && abs(ms) <= maxECMAScriptTime + msPerDay.Bun__msToGregorianDateTimepasses the empty value through as year 0, month 1, day 0, weekday 0. With year 0 the walk climbs about 100 million day steps back to year 275760, gets year 0 again, and repeats.On
mainbefore #42319 (WebKit dfd696443b, debug+ASAN build). These calls abort with thePlainGregorianDateTimeassertion:Bun.cron.parse("0 0 1 1 *", 8.64e15),Bun.cron.parse("0 0 30 2 *", new Date(8.64e15 - 86400000 * 400))with and without{ tz: "UTC" }, andBun.cron.parse("* * * * *", 8.64e15, { tz: "UTC" }). The assertion fires inside thems_to_gregorian_date_time_utccall that this PR bounds, when the walk reaches year 275761. Bun 1.4.3 (release) returnsnullfor all of them.* * * * *from 8.64e15 with a named zone takes 1 to 4.6 s there, because it walks 8 years one minute at a time. With this PR the walk ends after at most two days.Proof on both WebKit versions.
bun bd test test/js/bun/cron/cron-parse.test.ts, withsrc/at the base and then at this commit.main(6b394bf): 23 pass and 2 fail, then 25 pass. The parse test fails with exit code 134 and the assertion text. The scheduler test printsscheduledfor both clock values.mainafter Upgrade WebKit to cf1b36ec8703 #42319 (158ff6c, WebKit cf1b36ec8703) with this branch rebased on it: 23 pass and 2 fail, then 25 pass. Both tests time out and bun:test kills the child.Probe. 29 calls, each in a child process with a 20 s limit, on the debug build of 676b168 with and without the day bound, and on bun 1.4.3. Inputs:
* * * * *,0 0 1 1 *,0 0 30 2 *,0 0 13 9 *,0 0 14 9 *,0 12 13 9 *from 8.64e15, 8.64e15 - 1 minute, 8.64e15 - 10 days, 8.64e15 - 400 days and -8.64e15, in local time (TZ=UTC),UTC,America/New_YorkandAsia/Tokyo. Without the bound 10 calls hang. With the bound every result is equal to the 1.4.3 result.Every conversion in
next()is now inside the window that JSC converts.fromis inside the Date range. The noon of each day that the walk can reach is at most 8.64e15 + 12 h.resolve_local_matchprobes at most 121 minutes pastfrom. The lower end needs no bound, because the walk only moves forward. The bound keeps +275760-09-13 itself, so the last minute of the range still matches inPacific/Kiritimati(UTC+14, test row0 14 13 9 *).A candidate on the last day can resolve past 8.64e15. The local path returns a value above 8.64e15. The named-zone path returns NaN.
next()skips both and continues to the end of that day (at most 1440 more steps). Sonext()never returns a value outside the Date range. Before,cron_parsemapped such a value tonull, but the scheduler armed a timer for it: with the clock at exactly 8.64e15,Bun.cron("* * * * *", ...)scheduled a job. Now it throwshas no future occurrences, the same as a named zone.Test design. Both tests spawn a child, because a walk that does not stop spins in native code and cannot be interrupted. They are not concurrent: bun:test kills the children of a timed-out test only when the test is not concurrent. The
timeoutandkillSignalon the child are the kill switch for CI, where the per-test timeout is 90 s or more.Timing test. "impossible day/month (Feb 30) returns null quickly" asserts under 50 ms. It fails on a debug+ASAN build without this PR (159 ms). The first date conversion in a process costs about 150 ms there, and a warm call takes 2 ms. The test now makes one call before it starts the clock. #36894 has the same edit.
Relation to #36894. #36894 is closed in favor of this PR. It maps a match past 8.64e15 to
Noneinsidenext(), removes the clamp incron_parse, and guards the year inBun__gregorianDateTimeToMSInZone. This PR now does the first two. The year guard is not needed, because the walk cannot reach year 275761. #36894 does not bound the day walk, so it does not stop the loop on the new WebKit. Its{ tz }boundary rows are part of the new parse test here, and they pass.Not changed.
Cookie.cpp:261also callsmsToGregorianDateTime. On the new WebKitnew Bun.Cookie("a", "b", { expires: 1e13 }).toString()printsExpires=Sun, 00 Jan 0000 00:00:00 GMT. With the old WebKit it printedSun, 20 May 318857 17:46:40 GMT. Both are outside the Date range, and neither hangs.toISOStringinwtf-bindings.cpponly receives the time value of aDateor the current time.[human-review] gate passed · iteration 0 · 3 files touched
fails on main (without fix)
passes on PR (with fix)
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