### What does this PR do?
- **Use `Latin1Character` instead of `LChar`**
- **Fix for
0875bc8f62**
### How did you verify your code works?
---
# WebKit Update Summary (September 2025)
## Overview
This document summarizes the major changes in WebKit/JavaScriptCore from
the September 2025 update. The update includes approximately 254
JSC-related commits with significant improvements to performance,
stability, and developer experience.
## Critical Bug Fixes
### Memory Safety
- **operationMaterializeObjectInOSR fix** (5c7aadfa0a96): Fixed
uninitialized Butterfly storage during OSR exits with sunk Array
allocations. This prevents potential crashes when arrays with holes are
materialized during OSR exit.
- **FTL materialization fixes** (a72d19840714, ed1e6fe03899): Added
missing internal object type handling in FTL materialization, improving
stability during optimization bailouts.
### Promise and Async Improvements
- **JSPromiseReaction object** (a1cb5e087a46, later reverted in
b0566a4db201): Initially introduced to improve promise reaction handling
but was reverted due to compatibility issues with Bun's modifications.
- **Async stack traces enhancements**:
- Added support for `Promise.any` in async stack traces (d9a997b3edaa)
- Added empty JSValue checking for async stack trace safety
(9d26223d4bcb)
- Promise.all support was added and later reverted due to performance
concerns
## Performance Optimizations
### JIT Compiler Improvements
- **B3 Immutable Loads** (570a3530f949, 62300f8db3d9): Added
immutability annotations and CSE optimizations for loads that can look
for targets in dominators
- **BBQ JIT enhancements**:
- Fixed callee-save register handling (c7ae05719045)
- Simplified F32 copysign operations (e0651af57025)
- **DFG optimizations**:
- Fixed RegExp constant folding with materialized NewRegExp nodes
(7b53a04a5afa)
- Improved RegExp object node handling in strength reduction
(eeb65e05095b)
### WebAssembly Improvements
- **WASM SIMD Support**:
- Added v128 support for IPInt call and tail-call instructions
(73f0c9d430cb)
- Implemented v128 support in local.get, local.set, global.get,
global.set (67d7bf15139a)
- Added x86_64 SIMD integer arithmetic and float instructions
- **WASM Memory Management**:
- Introduced WasmInstanceAnchor for better instance lifecycle management
(f9f1ed183bf7)
- Attached AbstractHeap to wasm memory access for better optimization
(f183c6f7def4)
- Added signal handling for null checks in wasm (bf18b5b709f3)
- **WASM Debugging**: Added LLDB debugging infrastructure for
WebAssembly (e03c10225cc8)
## API and Language Features
### Iterator Helpers
- Merged `Iterator.prototype.sliding` into `Iterator.prototype.windows`
(1d49e823702d)
- Optimized iterator next method calls using CachedCall (5ee92514060c)
### Math Extensions
- Improved performance of `Math.sumPrecise` implementation
(602294057337)
### Error Handling
- Enhanced error messages for for-of loops without Symbol.iterator
(0051bbf2491f)
## Infrastructure Changes
### Character Type Refactoring
- **LChar to Latin1Character rename** (63b97b511366, 1424f0687876):
Major refactoring replacing the `LChar` type with `Latin1Character`
throughout the codebase for better clarity
- Additional fixes for Latin1Character usage (711eab3243f0,
50bf8e6fd4ca, 88e29ab76aec)
### Build System
- Fixed builds with GCC 15.x (e33b18bc59d6)
- Added gitattributes for JSC test files (82c4cc796da6)
- Improved test runner with comprehensive verbose logging (7ef95c177a42)
- Added memory-limited annotations for tests using excessive memory
(b991cd17d612)
### Testing Infrastructure
- Improved handling of missing test executables (db1e3bbb3be2)
- Added support for non-customized ICU 74.2 in intl tests (c922a28b6642)
- Fixed various test configuration issues and timeouts
## Bun-Specific Modifications
### Preserved Customizations
- Maintained `BUN_JSC_ADDITIONS` for Bun-specific features
- Kept async context support for AsyncLocalStorage
- Preserved V8 heap snapshot compatibility layer
- Maintained custom inspector extensions
### Conflicts Resolved
- Successfully merged upstream changes while preserving Bun's event loop
integration
- Resolved conflicts in promise handling while maintaining Bun's async
behavior
- Fixed re-declaration issues with `isAsyncFrame` for async stack traces
## Breaking Changes and Reverts
### Reverted Features
1. **JSPromiseReaction object**: Reverted due to conflicts with Bun's
promise handling
2. **Promise.all async stack trace support**: Reverted due to ~4%
performance regression in JetStream3/doxbee-async benchmark
3. **Array.prototype.flat C++ implementation**: Reverted (reason not
specified in commit)
## Security Improvements
- Type safety improvements with uncheckedDowncast for Wasm::Callee
(48425afd643d)
- Added bounds checking and validation for Wasm array operations
(b5148db1c4c1)
- Improved memory safety with proper initialization of materialized
objects
## Platform Support
- macOS: Continued support for x64/arm64
- Linux: Maintained glibc/musl compatibility
- Windows: Preserved x64 support
- Fixed platform-specific alignment issues for x86_64 (94a60eb123c5)
## Notable Debugging Enhancements
- LLDB infrastructure for WebAssembly debugging
- Improved verbose command logging in test runners
- Enhanced stack trace capabilities for async functions
- Better error reporting for missing Symbol.iterator
## Performance Metrics
- Several memory optimizations for test execution
- JIT memory reservation size adjustments for debug builds
- Optimized iterator operations with cached calls
- Improved Math.sumPrecise performance
## Future Considerations
- The JSPromiseReaction implementation may need revisiting with adjusted
architecture
- Async stack trace support for Promise.all requires performance
optimization
- Continued work on WASM SIMD support for additional operations
## Migration Notes for Bun Team
1. **LChar usage**: All references to `LChar` have been replaced with
`Latin1Character`
2. **Promise handling**: The reverted JSPromiseReaction changes indicate
potential architectural conflicts that may need addressing
3. **Test configuration**: New memory-limited annotations should be used
for memory-intensive tests
4. **Build flags**: Ensure USE_BUN_JSC_ADDITIONS and USE_BUN_EVENT_LOOP
remain enabled
* Enable more C++ warnings
* Only enable these ones in release builds
* Update MessagePortChannel.cpp
* Update BunProcess.cpp
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
* Use debug mode by default
* Enable build with assertions enabled
* Update cli.zig
* Update bun-linux-build.yml
* Fixes
* Fix `ASSERT_ENABLED`
* try this
* Update Dockerfile
* mimalloc debug
* Update CMakeLists.txt
* `Bun.deepMatch` - fix assertion failures
cc @dylan-conway, looks like we need to use `putDirectMayBeIndex` and check for `isCell` more carefully.
* Object.create support in code generator and callbacks wrapper
* Remove unused file
* zig upgrade
* zls
* Fix various errors
* Support `BuiltinAccessor` in create_hash_table script
* Fix assertion failure in `process.mainModule`
* Fix assertion failure in `onerror`
* Fix assertion failure when creating a Worker
* Fix asssertion failure when loading lots of files in bun test
* Fix assertion failure when termating a `Worker`
* Add helper for converting BunString to a WTFString
* Fix assertion failure in notifyNeedTermination
* Add more debug logs in `bun test`
* Fix compiler warning in usockets
* Fix assertion failure with `Worker` termination (another)
* Fix assertion failure in `coerceToInt64`
* Fix assertion failure in `BroadcastChannel`
* Fix assertion failure in `Headers.prototype.getAll`
* Fixes#7067
* Add heap analyzer label for CommonJS modules
* Fix assertion failure in module.require && module.require.resolve
* Remove unused code
* Fix assertion failure in debugger
* Fix crash in debugger
* Fix assertion failures in bun:sqlite
* Bump zig
* Bump WebKit
* Fix assertion failure in JSPromise::reject && JSInternalPromise::reject
* Fix assertion failure in ReadableStream::cancel
* Fix assertion failure in AsyncContextFrame::create
* Fix assertion failure in bun:sqlite
* Fix assertion failure in mocks
* Fix assertion failure in ServerWebSocket.close
* Fix assertion failure in N-API with subclasses
* [napi] Make promises cheaper
* undo
* Don't check for exceptions in ObjectInitializationScope
* Add separate entry point for test runner that doesn't generate code
* Don't deref builtin code
* Fix preload test
* Fix assertion failure in memoryUsage()
* Fix preload test, part 2
* Ensure that the env map for a Worker is empty after it is used
* The pointer for the Arena allocator used in parsing should not change
* Terminate thread on exit
* Start to implement scriptExecutionStatus
* Update worker.test.ts
* Fix Dirent.name setter
* Update settings.json
* Fix assertion failure in node:http
* Use correct value for `JSFinalObject::maxInlineCapacity`
* JSFinalObject::maxInlineCapacity x2
* Don't strip when assertions are enabled
* Make `m_wasTerminated` atomic
* Preserve directives in the transpiler
cc @ctjlewis
* Workaround assertion failure in ServerWebSocket.sendBinary and ServerWebSocket.sendText
* windows
* Buffer lockfile serialization in-memory
* PR feedback
* PR feedback
* PR feedback
* Windows
* quotes
* Update CMakeLists.txt
* Update bun-linux-build.yml
* Update bun-linux-build.yml
* Move this code to BunString.cpp
* Update BunString.cpp
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
* Fix memory leak in require() and add test
* Mark fixtures as generated code
* Add optimization for large files
* Fix small memory leak
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
* Prepare for windows event loop
* More progress
* Update libuv.zig
* wip
* Make compiling each dependency a shell script
* Bump mimalloc
* Add the build scripts
* Update settings.json
* Fix a bunch of compiler warnings
* Remove more warnings
* more warnings
* cmake works
* Update JSSQLStatement.h
* put it in the zig file
* Fix usockets warnings
* Fixup
* Fix one of the compiler errors
* chunk
* draw the rest of the owl
* theres more
* Rename Process -> BunProcess
Works around a Windows issue
* Add musl polyfill for memmem on Windows
* More
* 12 mb
* Fix getenvZ
* fix variosu issues
* Add fast-ish path for bun install on Windows
* Update windows.zig
* Update windows.zig
* Fix build issue
* it works
* hmmm
* Rename file
* Fixups
* Update wtf-bindings.cpp
* Update src/bun.js/bindings/headers-handwritten.h
Co-authored-by: Dylan Conway <35280289+dylan-conway@users.noreply.github.com>
* further!
* more
* Update .gitignore
* hm
* quite a lot of fixes
* Update CMakeLists.txt
* zig fmt
* Many more things are starting to work.
* reb
* regenaret
* Update JSSink.h
* fixup
* fetch works
* Bun.serve() and much of the event loop works now
* Make require() work
* bun install progress
* more things work
* use less std.os
* Fixes
* small fixes
* Bump
* Bummp
* Undo that change
* We have to bump the version of Debian because libarchive has a higher minimum requirement
* ok
* some clenaup
* windows
* Update bun.zig
* fixup
* avoid duplicate symbols
* avoid undefined symbols
* bump
* Remove issue template for install
It's not used, and use the bug issue instead.
* Add types for cp and cpSync
* Add types for watchFile and unwatchFile
* Add bun-types to 'bun fmt' script
* Update nodejs compat docs cp/cpSync/watchFile/unwatchFile (#4525)
* feat(fetch) rejectUnauthorized and checkServerIdentity (#4514)
* enable root certs on fetch
* rebase
* fix lookup
* some fixes and improvements
* fmt
* more fixes
* more fixes
* check detached onHandshake
* fix promise case
* fix cert non-Native
* add fetch tls tests
* more one test
* churn
* Update feature_flags.zig
* Update response.zig
* Revert "avoid undefined symbols"
This reverts commit ca835b726f.
* Revert "avoid duplicate symbols"
This reverts commit 4ac6ca8700.
* Update feature_flags.zig
* Set permissions
* more
* Update mimalloc
* Fix sqlite test failures
* Fix some test failures
* Make sure we remove libusockets is removed
* hm
* [dave]: fix webcrypto crash
* bump
* Update index.ts
* windows zig compiles
* cmake on mac works
* progress
* yay
* bun run build
* fix
* ok
* oops
* asdfasfdafdsafda
* fghjkl
* git ignore
* wow
* Process -> BunProcess
* hmm
* blah
* finalize merge
* now it only has linker errors on mac
* sdfadsf
* g
* getting farther
* sxdcvbnmk,
* adfhjskfjdhkas
* a
* fgh
* update build dot zig
* asdfg
* theoretical -DCANARY flag we can use
* asdf
* cool
* okay
* colorterm
* New build workflow
* Fix script
* Use sudo
* More sudo
* Tweak dependencies
* Another sudo attempt
* Tweak script
* 16.0 -> 16
* Tweak script
* Tweak script
* Tweak script
* Tweak script
* Tweak script
* bun install
* ssh into github actions
* add more to ssh
* Fix postinstal
* Skip llvm
* New dockerfile
* Build
* More changes to Dockerfile
* chaos chaos chaos
* okay
* a
* more cmake nonsense
* add unified sources code (does not work)
* stuff
* prepare for CI builds
* ok
* yay
* yeah
* make this more stable simply by trying again if it fails, 5 times, then lose. it fixes the stability issue i was running into L O L
* messing with ci
* x
* a
* clean dependencies before build
* oops
* this is not going to work but its closer
* not gonna work either
* a
* a
* did i do it
* a
* a
* work around weird fs+Bun.build issues
* properly pass debug flag correctly
* idk im sorry
* lose
* maybe
* run the tests please
* a
* fix zlib script
* a
* hi
* prevent stupid ci issue
* i totally didnt leave in a syntax error on cmakelists
* a
* lol
* relax
* 😭
* a
* SO SILLY
* 😡 one line mistake
* one character diff
* fix linking symbols missing
* work on dependency scripts
* does this work now?
* fix mac build
* a
* bump!
* woops
* add macos baseline build
* .
* fix sqlite and also enable $assert/$debug support in builtin functions
* okay
* oops
* zig upgrade lol
* Merge
* Fix spawn test issue
* Set a timeout
* yeah
* etc
* mi
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
Co-authored-by: Dylan Conway <35280289+dylan-conway@users.noreply.github.com>
Co-authored-by: Ashcon Partovi <ashcon@partovi.net>
Co-authored-by: Birk Skyum <74932975+birkskyum@users.noreply.github.com>
Co-authored-by: dave caruso <me@paperdave.net>
* WIP code coverage initial commit
* almost works
* one approach
* Code Coverage
* Update WebKit
* it works but is not yet accurate
* skip double ascii check
* wrapper
* it works but i'm not sure what to do about blocks
* hide blocks for now
* Update ZigSourceProvider.cpp
* Create coverage.md
* Update nav.ts
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
* stfdsafsd
sadffdsa
stuff
finish commonjs stuff
asdf
not done but work
not done but work
not done yet but this is how far i am
remove files
lol
update built files
uncomment everything in events lol
export default
stuff
* afdsafsd
* its not perfect but almost done
* okay
* cool
* remove temp file
* finish rebase
* revert settings.json
* a
* ch-ch-ch-ch-changes
* okay
* remove this check in release for now
* sxdcfghnjm,
* lkjhgf
* fmt
* filename can be null
* Update NodeModuleModule.h
* weee
* fmt
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
* wip changes for CommonJS
* this rewrite is almost complete
* even more code
* wip
* Remove usages of `import.meta.require` from builtins
* Remove usages of require
* Regenerate
* ✂️ builtin rewrite commonjs in printer
* Use lazy custom getters for import.meta
* fixups
* Remove depd
* ugh
* still crashing
* fixup undici
* comment out import.meta.require.resolve temporarily
not a real solution but it stops the crashes
* Redo import.meta.primordials
* Builtins now have a `builtin://` protocol in source origin
* Seems to work?
* Finsih getting rid of primordials
* switcharoo
* No more function
* just one more bug
* Update launch.json
* Implement `require.main`
* ✂️
* Bump WebKit
* Fixup import cycles
* Fixup improt cycles
* export more things
* Implement `createCommonJSModule` builtin
* More exports
* regenerate
* i broke some stuff
* some of these tests work now
* We lost the encoding
* Sort of fix zlib
* Sort of fix util
* Update events.js
* bump
* bump
* bump
* Fix missing export in fs
* fix some bugs with builtin esm modules (stream, worker_threads, events). its not perfect yet.
* fix some other internal module bugs
* oops
* fix some extra require default stuff
* uncomment this file but it crsahes on my machine
* tidy code here
* fixup tls exports
* make simdutf happier
* Add hasPrefix binding
* Add test for `require.main`
* Fix CommonJS evaluation order race condition
* Make node:http load faster
* Add missing exports to tls.js
* Use the getter
* Regenerate builtins
* Fix assertion failure in Bun.write()
* revamp dotEnv parser (#3347)
- fixes `strings.indexOfAny()`
- fixes OOB array access
fixes#411fixes#2823fixes#3042
* fix tests for `expect()` (#3384)
- extend test job time-out for `darwin-aarch64`
* `expect().resolves` and `expect().rejects` (#3318)
* Move expect and snapshots to their own files
* expect().resolves and expect().rejects
* Fix promise being added to unhandled rejection list
* Handle timeouts in expect(<promise>)
* wip merge
* Fix merge issue
---------
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
* fixup min/memcopy (#3388)
* Fix crash in builtins
* Don't attempt to evaluate modules with no source code
* Update WebCoreJSBuiltins.cpp
* Update WebCoreJSBuiltins.cpp
* Update WebCoreJSBuiltins.cpp
* Fix crash
* cleanup
* Fix test
cc @paperdave
* Fixup Undici
* Fix issue in node:http
* Create util-deprecate.mjs
* Fix several bugs
* Use the identifier
* Support error.code in `util.deprecate`
* make the CJs loader slightly more resilient
* Update WebCoreJSBuiltins.cpp
* Fix macros
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
Co-authored-by: dave caruso <me@paperdave.net>
Co-authored-by: Alex Lam S.L <alexlamsl@gmail.com>
Co-authored-by: Ashcon Partovi <ashcon@partovi.net>
Co-authored-by: Ciro Spaciari <ciro.spaciari@gmail.com>
