Test WebKit #742 preview: alternate signal stack for the threads of WTF

[robobun]

Do not merge. This pins WEBKIT_VERSION to autobuild-preview-pr-742-f6bee26d, the preview build of oven-sh/WebKit#742, so that the test suite of Bun runs against that build on every platform.

Why

• [WTF] Give WTF threads an alternate signal stack and make the suspend handler work on one WebKit#742 gives the threads that WTF creates an alternate signal stack. It also makes the suspend handler of WTF work when it runs on such a stack. It is stacked on [WTF] The signal handler runs on the alternate signal stack, and a thread that runs it there can be suspended WebKit#741, so this build has both.
• The CI of the WebKit fork runs tests on Linux x64 and arm64 with glibc only. I have no macOS machine.
• test/js/bun/jsc-stress/testFFI.test.ts runs the testFFI binary of the WebKit build. That binary has three new tests from [WTF] Give WTF threads an alternate signal stack and make the suspend handler work on one WebKit#742, and two of them run on macOS.

What to read in the result

• testFFI.test.ts on macOS and on musl.
• The rest of the suite on macOS, where the threads of WTF get the alternate stack too.

I close this PR when the run is done and copy the result to oven-sh/WebKit#742. The pin for the real change is in #40169.

[robobun]

Closing: the run is done, and this PR is not for merge.

Result of build 121721 with the preview build of oven-sh/WebKit#742 (autobuild-preview-pr-742-f6bee26d): all 181 jobs pass.

test/js/bun/jsc-stress/testFFI.test.ts (1 pass, 0 fail) ran the testFFI of that build on:

• macOS aarch64 and x64
• Alpine 3.23 aarch64 and x64 (musl)
• Debian 13 x64 and Ubuntu 25.04 aarch64

The build jobs of macOS and musl show the download of that preview build and testFFI in the profile archive. FreeBSD and Android are built, not tested.

[robobun]

Reopened for one more run: oven-sh/WebKit#742 has a new head (f51a066e36) with one more testFFI test, which runs on macOS too. I close this again when the run is done.

[robobun]

^{Updated 10:51 PM PT - Sep 29th, 2026}

✅ @robobun, your commit 9ffbe5bc5522517137dbcbbf332f378a2799a03a passed in Build #121790! 🎉

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🧪   To try this PR locally:

bunx bun-pr 44260

That installs a local version of the PR into your bun-44260 executable, so you can run:

bun-44260 --bun

[robobun]

Closing again: the second run is done, and this PR is not for merge.

Result of build 121790 with the preview build of the head of oven-sh/WebKit#742 (autobuild-preview-pr-742-f51a066e): all 181 jobs pass.

test/js/bun/jsc-stress/testFFI.test.ts (1 pass, 0 fail) ran the testFFI of that build on macOS aarch64 and x64, Alpine 3.23 aarch64 and x64, Debian 13 x64 and Ubuntu 25.04 aarch64. That testFFI has the test that was added since the first run: when a thread of WTF ends, no alternate signal stack is registered, and a stack that the thread registered itself stays registered.