## Summary
- Fix crash in `FormData.from()` when called with very large ArrayBuffer
input
- Add length check in C++ `toString` function against both Bun's
synthetic limit and WebKit's `String::MaxLength`
- For UTF-8 tagged strings, use simdutf to calculate actual UTF-16
length only when byte length exceeds the limit
## Root Cause
When `FormData.from()` was called with a very large ArrayBuffer (e.g.,
`new Uint32Array(913148244)` = ~3.6GB), the code would crash with:
```
ASSERTION FAILED: data.size() <= MaxLength
vendor/WebKit/Source/WTF/wtf/text/StringImpl.h(886)
```
The `toString()` function in `helpers.h` was only checking against
`Bun__stringSyntheticAllocationLimit` (which defaults to ~4GB), but not
against WebKit's `String::MaxLength` (INT32_MAX, ~2GB). When the input
exceeded `String::MaxLength`, `createWithoutCopying()` would fail with
an assertion.
## Changes
1. **helpers.h**: Added `|| str.len > WTF::String::MaxLength` checks to
all three code paths in `toString()`:
- UTF-8 tagged pointer path (with simdutf length calculation only when
needed)
- External pointer path
- Non-copying creation path
2. **url.zig**: Reverted the incorrect Zig-side check (UTF-8 byte length
!= UTF-16 character length)
## Test plan
- [x] Added test that verifies FormData.from with oversized input
doesn't crash
- [x] Verified original crash case now returns empty FormData instead of
crashing:
```js
const v3 = new Uint32Array(913148244);
FormData.from(v3); // No longer crashes
```
🤖 Generated with [Claude Code](https://claude.com/claude-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>
* Move ReadFile and WriteFile to separate file
* Use libuv for Bun.write()
* Update windows_event_loop.zig
* build
* Get bun-write tests to pass. Implement Bun.write with two files.
* UPdate
* Update
* Update failing test list
* update
* More
* More
* More
* More
* Mark the rest
* ok
* oops
* Update bun-write.test.js
* Update blob.zig
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
Co-authored-by: Dave Caruso <me@paperdave.net>
Co-authored-by: Georgijs Vilums <georgijs.vilums@gmail.com>
* WIP
* WIP
* WIP
* WIP
* Improve typechecking in type files
* Fix typechecking
* Update
* Update submodule
* CI for typechecking
* Add ci
* Update commands
* Format after build
* Dont use bunx
* Rename job
* Use nodemodules prettier
* Update workflow
* Use symlink
* Debug
* Debug
* Clean up and rename jobs
* Fix test
* Fix segfault when unexpected type is passed in `expect().toThrow`
* Fix issues with request constructor
* Don't bother cloning headers when its empty
* woops
* more tests
* fix incorrect test
* Make the fetch error messages better
* Update response.zig
* Fix test that failed on macOS
* Fix test
* Remove extra hash table lookups
* Support running dummy registry directly
cc @alexlamsl
* Update test
* Update test
* fixup
* Workaround crash in test runner
* Fixup test
* Fixup test
* Update os.test.js
---------
Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
