### 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
### What does this PR do?
**This PR is created because [the previous PR I
opened](https://github.com/oven-sh/bun/pull/21728) had some concerning
issues.** Thanks @Jarred-Sumner for the help.
The goal of this PR is to introduce PUB/SUB functionality to the
built-in Redis client. Based on the fact that the current Redis API does
not appear to have compatibility with `io-redis` or `redis-node`, I've
decided to do away with existing APIs and API compatibility with these
existing libraries.
I have decided to base my implementation on the [`redis-node` pub/sub
API](https://github.com/redis/node-redis/blob/master/docs/pub-sub.md).
#### Random Things That Happened
- [x] Refactored the build scripts so that `valgrind` can be disabled.
- [x] Added a `numeric` namespace in `harness.ts` with useful
mathematical libraries.
- [x] Added a mechanism in `cppbind.ts` to disable static assertions
(specifically to allow `check_slow` even when returning a `JSValue`).
Implemented via `// NOLINT[NEXTLINE]?\(.*\)` macros.
- [x] Fixed inconsistencies in error handling of `JSMap`.
### How did you verify your code works?
I've written a set of unit tests to hopefully catch the major use-cases
of this feature. They all appear to pass.
#### Future Improvements
I would have a lot more confidence in our Redis implementation if we
tested it with a test suite running over a network which emulates a high
network failure rate. There are large amounts of edge cases that are
worthwhile to grab, but I think we can roll that out in a future PR.
### Future Tasks
- [ ] Tests over flaky network
- [ ] Use the custom private members over `_<member>`.
---------
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
### What does this PR do?
### How did you verify your code works?
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
## Summary
- Fixes unnecessary regeneration of `bun_dependency_versions.h` on every
CMake run
- Only writes the header file when content actually changes
## Test plan
Tested locally by running CMake configuration multiple times:
1. First run generates the file (shows "Updated dependency versions
header")
2. Subsequent runs skip writing (shows "Dependency versions header
unchanged")
3. File modification timestamp remains unchanged when content is the
same
4. File is properly regenerated when deleted or when content changes
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
### What does this PR do?
Evidently, Ubuntu turns them on by default.
Claude:
```
> What is the typical overhead for glibcxx assertions?
⏺ The overhead of glibc/libstdc++ assertions can be significant, especially in
performance-critical code:
Typical Overhead Ranges:
libstdc++ (C++ standard library) assertions:
- 5-15% overall performance impact in typical applications
- Up to 30-50% in container-heavy code (vectors, maps, etc.)
- Iterator validity checks are particularly expensive
glibc (C library) assertions:
- 2-8% overall impact in typical applications
- Up to 20% in malloc/free intensive code
- Heap consistency checks, buffer overflow detection
```
## Summary
This PR introduces a CMake-generated header file containing all
dependency versions, eliminating the need for C++ code to depend on
Zig-exported version constants.
## Changes
- **New CMake script**: `cmake/tools/GenerateDependencyVersions.cmake`
that:
- Reads versions from the existing `generated_versions_list.zig` file
- Extracts semantic versions from header files where available
(libdeflate, zlib)
- Generates `bun_dependency_versions.h` with all dependency versions as
compile-time constants
- **Updated BunProcess.cpp**:
- Now includes the CMake-generated `bun_dependency_versions.h`
- Uses `BUN_VERSION_*` constants instead of `Bun__versions_*`
- Removes dependency on Zig-exported version constants
- **Build system updates**:
- Added `GenerateDependencyVersions` to main CMakeLists.txt
- Added build directory to include paths in BuildBun.cmake
## Benefits
✅ Single source of truth for dependency versions
✅ Versions accessible from C++ without Zig exports
✅ Automatic regeneration during CMake configuration
✅ Semantic versions shown where available (e.g., zlib 1.2.8 instead of
commit hash)
✅ Debug output file for verification
## Test Results
Verified that `process.versions` correctly shows all dependency
versions:
```javascript
$ bun -e "console.log(JSON.stringify(process.versions, null, 2))"
{
"node": "24.3.0",
"bun": "1.2.22-debug",
"boringssl": "29a2cd359458c9384694b75456026e4b57e3e567",
"libarchive": "898dc8319355b7e985f68a9819f182aaed61b53a",
"mimalloc": "4c283af60cdae205df5a872530c77e2a6a307d43",
"webkit": "0ddf6f47af0a9782a354f61e06d7f83d097d9f84",
"zlib": "1.2.8",
"libdeflate": "1.24",
// ... all versions present and correct
}
```
## Generated Files
- `build/debug/bun_dependency_versions.h` - Header file with version
constants
- `build/debug/bun_dependency_versions_debug.txt` - Human-readable
version list
🤖 Generated with [Claude Code](https://claude.ai/code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
### What does this PR do?
Enables async stack traces
### How did you verify your code works?
Added tests
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
### What does this PR do?
### How did you verify your code works?
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
ebe0cdac31..e0b7c318f3
It hides it in typeInfo even in the current file, unlike private
declarations which are only hidden in other files.
This allows you to formatted print a type with private fields, but the
private fields are not shown. The alternative would be to allow
accessing private fields through `@field()` but that looked like it was
going to be more complicated (need to add an argument to
structFieldVal/structFieldPtr which are called by fieldVal/fieldPtr
which have 36 callsites)
---------
Co-authored-by: taylor.fish <contact@taylor.fish>
ZLS was tested manually and works with private fields (after restarting)
Zig diff:
d1a4e0b0dd..ebe0cdac31
ZLS diff:
15730e8e5d..3733f39c8d
Increases `zig build check` time by maybe 10ms?
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
### What does this PR do?
### How did you verify your code works?
---------
Co-authored-by: Jarred-Sumner <709451+Jarred-Sumner@users.noreply.github.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
## Summary
- Updates WebKit commit from `684d4551ce5f62683476409d7402424e0f6eafb5`
to `aa4997abc9126f5a7557c9ecb7e8104779d87ec4`
- Build completed successfully with no errors
- Verified functionality with hello world test
## Test plan
- [x] Build completed successfully
- [x] Hello world test passes with `bun bd`
- [x] No build errors encountered
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
## Summary
- Updates WebKit from 75f6499 to eb92990 (latest release from
oven-sh/webkit)
- This brings in the latest WebKit improvements and fixes
## Test plan
- [ ] Verify the build completes successfully
- [ ] Run existing test suite to ensure no regressions
🤖 Generated with [Claude Code](https://claude.ai/code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
### What does this PR do?
<!-- **Please explain what your changes do**, example: -->
<!--
This adds a new flag --bail to bun test. When set, it will stop running
tests after the first failure. This is useful for CI environments where
you want to fail fast.
-->
### How did you verify your code works?
ran fuzzy-wuzzy.test.ts
<!-- **For code changes, please include automated tests**. Feel free to
uncomment the line below -->
<!-- I wrote automated tests -->
<!-- If JavaScript/TypeScript modules or builtins changed:
- [ ] I included a test for the new code, or existing tests cover it
- [ ] I ran my tests locally and they pass (`bun-debug test
test-file-name.test`)
-->
<!-- If Zig files changed:
- [ ] I checked the lifetime of memory allocated to verify it's (1)
freed and (2) only freed when it should be
- [ ] I included a test for the new code, or an existing test covers it
- [ ] JSValue used outside of the stack is either wrapped in a
JSC.Strong or is JSValueProtect'ed
- [ ] I wrote TypeScript/JavaScript tests and they pass locally
(`bun-debug test test-file-name.test`)
-->
<!-- If new methods, getters, or setters were added to a publicly
exposed class:
- [ ] I added TypeScript types for the new methods, getters, or setters
-->
<!-- If dependencies in tests changed:
- [ ] I made sure that specific versions of dependencies are used
instead of ranged or tagged versions
-->
<!-- If a new builtin ESM/CJS module was added:
- [ ] I updated Aliases in `module_loader.zig` to include the new module
- [ ] I added a test that imports the module
- [ ] I added a test that require() the module
-->
