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TypedArray indexOf / lastIndexOf / includes: never match a wrapped, rounded or truncated search value (WebKit bump for oven-sh/WebKit#609) - #42093
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…ounded or truncated search value (WebKit bump for oven-sh/WebKit#609) Pin WebKit to the preview build of oven-sh/WebKit#609 and add a test for all twelve element types. Uint8ClampedArray matched a double needle modulo 256 in LTO release builds, Float32Array / Float16Array rounded an int32 needle, and BigInt64Array / BigUint64Array reduced a BigInt needle modulo 2^64.
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Included review availability: Your plan provides up to 10 included reviews per hour; 0 remain after this review. WalkthroughChangesThe build now selects an autobuild preview WebKit release tag. Typed-array tests cover WebKit release selection
Typed-array search coverage
Merge Risk: 🟡 Moderate · up to Final builds remain tied to a temporary WebKit preview rather than the immutable merged commit, so reproducibility is not finalized. Merge after WebKit#609 lands and the dependency pin is updated. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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In `@scripts/build/deps/webkit.ts`:
- Line 6: After oven-sh/WebKit#609 merges, replace the temporary
autobuild-preview-pr-609-7a274ac4 value in WEBKIT_VERSION with the immutable
merged commit SHA, and update the matching process.versions assertion to the
same SHA.
In `@test/js/bun/jsc/typed-array-search-needle.test.ts`:
- Line 40: Replace the for...of parameterization in the typed-array search tests
with describe.each() tables for both the needle matrix and TypedArray matrix,
creating distinct test cases for every combination while preserving the existing
assertions and behavior.
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scripts/build/deps/webkit.tstest/js/bun/jsc/typed-array-search-needle.test.ts
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| * From https://github.com/oven-sh/WebKit releases. | ||
| */ | ||
| export const WEBKIT_VERSION = "2e2aa2290fac856d6f451ceacb58f7f5b44dd057"; | ||
| export const WEBKIT_VERSION = "autobuild-preview-pr-609-7a274ac4"; |
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🔴 WEBKIT_VERSION is pinned to autobuild-preview-pr-609-7a274ac4, an ephemeral preview-build tag for an unmerged PR; once oven-sh/WebKit#609 merges or its preview release is GC'd, fresh checkouts of main will 404 fetching the prebuilt tarball and fail to build. Fix: before merge, swap this to the merged upstream commit SHA (per landing-prs.md "Dependencies & vendoring" and this file's own doc comment, which reserves --webkit-version=<hash> for testing branches) and confirm prebuilt artifacts exist for every platform × flavor. The PR description already states "Do not merge before oven-sh/WebKit#609 lands" — this comment tracks that as the merge blocker.
Extended reasoning...
prebuiltUrl() (webkit.ts:68-75) builds https://github.com/oven-sh/WebKit/releases/download/autobuild-preview-pr-609-7a274ac4/bun-webkit-<os>-<arch><suffix>.tar.gz. Preview tags on oven-sh/WebKit are ephemeral artifacts of unmerged PRs; when PR #609 merges (a new autobuild-<merge-sha> tag is cut) or is superseded/closed, the preview release can be deleted, and any developer or CI lane doing a fresh build then hits a 404 in the dep_fetch step and cannot build bun. The base pin 2e2aa2290fac856d6f451ceacb58f7f5b44dd057 is a permanent release SHA and does not have this failure mode. The repo's own review rule (.claude/docs/landing-prs.md, Dependencies & vendoring) makes this merge-blocking: "Never merge a pin to an ephemeral artifact (preview tags, unmerged-PR builds)." The author acknowledges this in the PR description; filing so it is not lost before merge.
Verification: normal — acknowledged in diff: the PR description states "The pin is a preview tag, not a merge commit. Do not merge before oven-sh/WebKit#609 lands. I move the pin to the merged commit then." That claim is accurate and matches the required fix. /home/claude/bun/scripts/build/deps/webkit.ts:6 changes WEBKIT_VERSION from the stable SHA 2e2aa2290fac856d6f451ceacb58f7f5b44dd057 to… | normal —…
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Agreed, this is the merge blocker. The pin moves to the merged oven-sh/WebKit commit (a permanent autobuild-<sha> release with every platform and flavor) once oven-sh/WebKit#609 lands, and this thread gets resolved by that push.
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Status Reproduced with bun 1.4.2 (
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…ows from #42083 and #42089 Adds the rows those two PRs pinned that this file did not have yet: negative int32 needles and arithmetic results on Float32Array, the 65505..65519 and 65535 needles on Float16Array, more wrapped BigInt needles (negative many-digit, -(2^64) +/- 1, -(2^63) - 1 on BigUint64Array), and the same searches through a subarray, a resizable buffer, a shared buffer, and with a fromIndex.
…path) Once ArithNegate has produced -0 the optimizing tiers hand indexOf a double, so a program that was correct cold started matching (-i) mod 256 after tier-up in release builds. Same conversion path as the cold double needles; bun 1.4.2 records 483 wrong matches here, the preview build 0.
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Code review found no new issues
No new issues were found in this update; 1 finding from earlier reviews is still open above.
Still open from earlier reviews (1):
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scripts/build/deps/webkit.ts:6—WEBKIT_VERSION is pinned to autobuild-preview-pr-609-7a274ac4, an ephemeral preview-build tag for an unmerged PR; once…
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Problem
Uint8ClampedArray.prototype.indexOf,lastIndexOfandincludesmatch a byte that is not there when the search value is a double outside 0..255, in release builds only:new Uint8ClampedArray([7, 0, 255]).indexOf(x)is 2 forx = -1(double) and 1 for256,1e10,2 ** 31,Infinity. Every build also hasnew Float32Array([16777216]).indexOf(16777217) === 0,new Float16Array([Infinity]).indexOf(65536) === 0andnew BigInt64Array([1n]).includes(2n ** 64n + 1n) === true. V8 answers -1 / false for all of them.toNativeFromValueWithoutCoercion<Adaptor>()(runtime/ToNativeFromValue.h), which turns the search value into an element value before the scan. Its BigInt path used the modularToBigInt64/ToBigUint64, its int32 path for float element types cast with no round-trip check, and its double path forUint8Clampeddidstatic_cast<uint8_t>(double), undefined behavior outside (-1, 256), which the LTO link folds into "is the double integral" (see Background).Fix
autobuild-preview-pr-609-7a274ac4, the preview build of [JSC] TypedArray indexOf / lastIndexOf / includes: never wrap, clamp or round the search value WebKit#609. That change makes all three paths return "not representable" instead of a wrapped, rounded or truncated value, and moves the float adaptors' range check before the narrowing cast.mainpast the current pin. ([JSC] TypedArray indexOf / lastIndexOf / includes: never wrap, clamp or round the search value WebKit#609 has one later commit, 1f8219282c, that only touches its JSTests stress test, so this preview'sSource/is what merges.)test/js/bun/jsc/typed-array-search-needle.test.ts(new, 9 tests over all 12 element types, including a warmedu8c.indexOf(-i)whose needle only becomes a double after DFG tier-up). bun 1.4.2 (release, LLD 22.1.8 link) fails 7 of them (bothUint8ClampedArraytests,Float32Array,Float16Arrayand the three BigInt tests), a non-LTO or debug build ofmainfails 5 (everything but theUint8ClampedArray, integer-type andFloat64Arraytests), andbun bd testwith this pin (debug + ASAN) passes all 9. [JSC] TypedArray indexOf / lastIndexOf / includes: never wrap, clamp or round the search value WebKit#609 lists the JSC-side runs (new stress test, 714 test262 TypedArray search cases, the typed-array stress tests).Supersedes #42083 and #42089
Float32Array/Float16Arrayint32 path) and BigInt64Array / BigUint64Array indexOf, lastIndexOf, includes: an out-of-range BigInt needle matches nothing (WebKit bump for oven-sh/WebKit#607) #42089 (bump for [JSC] BigInt64Array / BigUint64Array indexOf, lastIndexOf and includes: an out-of-range BigInt needle matches nothing WebKit#607, theBigInt64Array/BigUint64Arraypath) each fixed one of the three paths. [JSC] TypedArray indexOf / lastIndexOf / includes: never wrap, clamp or round the search value WebKit#609 changes the same helper and contains both of those fixes plus theUint8Clampeddouble path, so both pairs are closed in favour of this PR and [JSC] TypedArray indexOf / lastIndexOf / includes: never wrap, clamp or round the search value WebKit#609.typed-array-search-needle.test.ts: negative and computed int32 needles onFloat32Array, the 65505..65519 and 65535 needles onFloat16Array, more wrapped BigInt needles (negative many-digit values,-(2n ** 64n) ± 1n,-(2n ** 63n) - 1nonBigUint64Array), and the same searches through a subarray, a resizable buffer, a shared buffer, and with afromIndex.Background
indexOf/lastIndexOf, SameValueZero forincludes). JSC converts the search value to the element type once and scans raw storage withmemchr-style helpers, which is only equivalent when that conversion is exact. The helper returnsstd::optionalfor that reason.Uint8Clampedface: the check after the cast,static_cast<double>(integer) != value, isuitofp (fptoui x)compared withxin LLVM IR, and an out-of-rangefptouiis poison. LLVM 22 folds that pair intoftrunc xwhen only a compare observes it. bun's release link is ThinLTO through rust-lld (LLD 22.1.8), so the-ltoWebKit prebuilt's bitcode is code-generated by LLVM 22, while the non-LTO prebuilt (localbuild:release,release-asan, debug) is compiled by clang 21, which keeps the round trip. In bun 1.4.2 the fold is visible asroundsd $0xb; ucomisdattypedArrayViewProtoFuncIncludes+0xcfb, and the needle that is then searched for is the low byte of a 32-bitcvttsd2si.IntegralTypedArrayAdaptor(Int8 through Uint32) withtruncateDoubleToInt64, which is why those element types were already correct.Notes
-O3 -flto=thin) and linked with--ld-path=<rustup nightly-2026-07-20>/gcc-ld/ld.lldemitscvttsd2si %xmm0,%eax; roundsd $0xb,%xmm0,%xmm1and reports1e10found at index 1; the fixed conversion emitscvttsd2si %xmm0,%rax; cvtsi2sdand is correct. Plain clang 21-O3keeps the round trip in both.-ltoprebuilt'sJSTypedArrayViewPrototypeFunctions2.cpp.obitcode through the same LLD 22.1.8 with--lto-emit-asmgives oneroundsd $11+ 32-bitcvttsd2siin each oftypedArrayViewProtoFuncIncludes/IndexOffor the old pin (attributed toTypedArrayAdaptors.h:340by the line table) and none for the preview, which has a 64-bitcvttsd2si+movzblatTypedArrayAdaptors.h:343instead.BUN_JSC_useJIT=0made no difference, as the report observed.[policy-decision:webkit] gate passed · iteration 0 · 2 files touched
passes on PR (with fix)
diff hotspot
gate history · 3 passed · 0 rejected · iteration 0
evidence per changed file
root cause · written by the author bot
The typed array
indexOf,lastIndexOf, andincludesfast paths converted the search value from a double straight into the element's storage type with a cast that is undefined behavior when the value is out of range, so needles like-1,256,1e10, orInfinityended up wrapping modulo 256 forUint8ClampedArrayand spuriously matching an unrelated byte. The fix replaces the unchecked cast with an explicit round-trip check: the double is converted to the element type and converted back, and the search proceeds only if the result is exactly equal to the original value, otherwise t…