Blog

Bun v1.4.2

Dylan Conway

This release fixes two regressions impacting Elysia and

AsyncLocalStorage

, a hang in

@discordjs/ws

, CMYK JPEG decoding in

Bun.Image

, a rare JIT crash, and a GC crash on musl.

To install Bun

curl

      curl -fsSL https://bun.sh/install | bash
    

npm

      npm install -g bun
    

powershell

      powershell -c "irm bun.sh/install.ps1|iex"
    

scoop

      scoop install bun
    

brew

      brew tap oven-sh/bun
    

      brew install bun
    

docker

      docker pull oven/bun
    

      docker run --rm --init --ulimit memlock=-1:-1 oven/bun
    

To upgrade Bun

      bun upgrade
    

Fixed: bun build variable name collision#

A regression introduced in Bun v1.4.1 impacting Elysia caused

bun build

to rename a nested

var

to the same name as a

let

in the same block. Builds importing Elysia would fail to load with

SyntaxError: Cannot declare a var variable that shadows a let/const/class variable

. This has been fixed and a regression test has been added.

index.js

      function foo () {
  {
    let exports2 = {};
    var exports = exports2;
  }
  return exports;
}
module.exports = foo();
    

bun build index.js --outfile out.js

would output code containing:

out.js

      // inside CJS module wrapper
function foo() {
  {
    let exports2 = {};
    var exports2 = exports2; // SyntaxError
  }
  return exports2;
}
module.exports = foo();
    

The same bug could also give a

let

the name of a function parameter or

catch

binding, producing code that evaluates but computes incorrect values.

Fixed: AsyncLocalStorage memory leak#

A regression introduced in Bun v1.4.1 caused a timer, immediate, or pending promise created inside

store.exit()

or a nested

store.run()

to keep the outer store value alive for as long as that timer or promise existed.

getStore()

still returned the correct value, so only memory usage was affected. This has been fixed.

      const store = new AsyncLocalStorage();

store.run(bigPerRequestContext, () => {
  store.exit(() => setTimeout(() => {}, 3_600_000));
  // kept bigPerRequestContext alive for an hour
});
    

Fixed: worker_threads 'online' event order#

A

Worker

from

node:worker_threads

didn't emit

'online'

first, causing

@discordjs/ws

to hang due to missing a worker's first message. The order now matches Node.js.

      import { Worker, isMainThread, parentPort } from "worker_threads";
import { once } from "events";

if (isMainThread) {
  const worker = new Worker(new URL(import.meta.url));
  await once(worker, "online");
  worker.on("message", (msg) => {
    console.log(msg); // never received in v1.4.1
  });
} else {
  parentPort.postMessage("hi");
}
    

Fixed: Bun.Image decodes CMYK and YCCK JPEGs#

Bun.Image

now decodes 4-component CMYK and YCCK JPEGs. Previously these failed with

Image: decode failed

. They are converted to RGB on decode, so every transform and output format works.

      await new Bun.Image("photo-cmyk.jpg").resize(400, 400).webp().bytes();
    

Upgraded JavaScriptCore#

Bun v1.4.2 pulls in about 350 more upstream WebKit commits. They include

Intl

and TypedArray correctness fixes, a fix for a

Proxy

crash, and cheaper

Date

objects.

      new Intl.PluralRules("en").select(1n); // => "one" (was TypeError)
    

• new Int32Array(array) (and the other TypedArray constructors) read a stale or missing element when an element's valueOf mutated array during conversion.
• TypedArray.prototype.slice into a Symbol.species view that overlaps its source on the same buffer now copies in spec order.
• Intl.DurationFormat with style: "digital" no longer prints a stray : when minutes is 0 and hidden.
• Object.setPrototypeOf(handler, null) on a Proxy handler that had already served a trap could crash when the handler came from a class defined inside a function called many times.

Bugfixes#

• Fixed: a rare crash in long-running processes after a prototype that JIT-optimized code had cached property lookups through was garbage-collected.

• Fixed: on musl (Alpine), Array.prototype.splice, shift, or shrinking array.length on an array of objects could crash on a GC thread or hang if it ran while the GC was marking.

• Fixed: .json() on a Response, Blob, Bun.file(), or proc.stdout rejected invalid JSON with a generic Failed to parse JSON instead of the SyntaxError message JSON.parse gives, such as JSON Parse error: Expected '}'.

• Fixed: bun install and bun add could panic with range end index out of range when bun.lockb or a cached registry manifest stored a package-name hash that didn't match the name.

• Fixed: on Linux, if registering a Bun.file().writer() FileSink with epoll failed (for example fs.epoll.max_user_watches exhausted), its file descriptor was closed twice, which could close an unrelated descriptor that reused the number.