Intent to Ship: WebAssembly Exception Handling

[Andreas Haas]

Contact emails

thib...@chromium.org, ah...@chromium.org, va...@chromium.org, ahe...@chromium.org

Explainer

https://github.com/aheejin/exception-handling

Specification

https://github.com/WebAssembly/exception-handling

Summary

This feature is adding exception support to WebAssembly. Exception handling allows code to break control flow when an exception is thrown. The exception can be any exception known by the WebAssembly module, or it may be an unknown exception that was thrown by a called imported function.

Blink component

Blink>JavaScript>WebAssembly

Search tags

wasm, webassembly, Exceptions

TAG review

Not required for WebAssembly feature launches

TAG review status

Not applicable

Risks

Interoperability and Compatibility

Gecko: Positive (https://bugzilla.mozilla.org/show_bug.cgi?id=1335652)

WebKit: Positive They're probably not likely to begin working on the proposal before stage 3

Web developers: The developer feedback on the spec proposal (https://github.com/WebAssembly/exception-handling) was positive. This feature is one of the last bits missing to port legacy c++ apps to the web. Code that uses WebAssembly Exception Handling can be generated by Emscripten and has been used successfully in the origin trial. 

Debuggability

Supported using DevTools

Is this feature fully tested by web-platform-tests?

Yes, tests are provided by the spec, see https://github.com/WebAssembly/exception-handling/tree/master/test.

Flag name

WebAssembly Exception handling can be enabled and disabled by the V8 Flag: --experimental-wasm-eh.

Requires code in //chrome?

No

Tracking bug

https://bugs.chromium.org/p/v8/issues/detail?id=8091

Launch bug

https://bugs.chromium.org/p/chromium/issues/detail?id=1173515

Estimated milestones

OriginTrial desktop first	90
OriginTrial desktop last	94
OriginTrial android first	90
OriginTrial android last	94

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/4756734233018368

Links to previous Intent discussions

Intent to Experiment: https://groups.google.com/a/chromium.org/g/blink-dev/c/7l3oDJuNs6o/m/MtlFURU1BAAJ

This intent message was generated by Chrome Platform Status.

[Yoav Weiss]

On Tuesday, August 24, 2021 at 11:04:33 AM UTC+2 Andreas Haas wrote:

Contact emails

thib...@chromium.org, ah...@chromium.org, va...@chromium.org, ahe...@chromium.org

Explainer

https://github.com/aheejin/exception-handling

Specification

https://github.com/WebAssembly/exception-handling

Summary

This feature is adding exception support to WebAssembly. Exception handling allows code to break control flow when an exception is thrown. The exception can be any exception known by the WebAssembly module, or it may be an unknown exception that was thrown by a called imported function.

Blink component

Blink>JavaScript>WebAssembly

Search tags

wasm, webassembly, Exceptions

TAG review

Not required for WebAssembly feature launches

TAG review status

Not applicable

Risks

Interoperability and Compatibility

Gecko: Positive (https://bugzilla.mozilla.org/show_bug.cgi?id=1335652)

Looks like they shipped (or at least fully implemented), so that's definitely a strong signal :)

 

WebKit: Positive They're probably not likely to begin working on the proposal before stage 3

Links?

Any conclusions/feedback from the Origin Trial?

[Andreas Haas]

The conclusion/feedback from the OT was that we've shown that the WebAssembly Exceptions work well with the C++ toolchain that targets it, and that it had the desired impact (i.e. exception-using code is much smaller and faster).

We targeted the OT to specific partners, and it enabled those partners to deploy to users and validate WebAssembly Exceptions based on their usage. 

[Andreas Haas]

Here is a link to the toolchain that targeted the OT: https://emscripten.org/docs/porting/exceptions.html

[Lars Hansen]

On Wednesday, August 25, 2021 at 3:56:34 PM UTC+2 yoav...@chromium.org wrote:

On Tuesday, August 24, 2021 at 11:04:33 AM UTC+2 Andreas Haas wrote:

Contact emails

thib...@chromium.org, ah...@chromium.org, va...@chromium.org, ahe...@chromium.org

Explainer

https://github.com/aheejin/exception-handling

Specification

https://github.com/WebAssembly/exception-handling

Summary

This feature is adding exception support to WebAssembly. Exception handling allows code to break control flow when an exception is thrown. The exception can be any exception known by the WebAssembly module, or it may be an unknown exception that was thrown by a called imported function.

Blink component

Blink>JavaScript>WebAssembly

Search tags

wasm, webassembly, Exceptions

TAG review

Not required for WebAssembly feature launches

TAG review status

Not applicable

Risks

Interoperability and Compatibility

Gecko: Positive (https://bugzilla.mozilla.org/show_bug.cgi?id=1335652)

Looks like they shipped (or at least fully implemented), so that's definitely a strong signal :)

We have an incomplete implementation (available behind a flag in Nightly, not on by default even there) and have not in any sense shipped anything.  We do not (to my knowledge) have any publicly stated position on this spec, apart from that bug and an intent-to-prototype.

--lars

[Yoav Weiss]

On Thursday, August 26, 2021 at 8:58:29 PM UTC+2 lha...@mozilla.com wrote:

On Wednesday, August 25, 2021 at 3:56:34 PM UTC+2 yoav...@chromium.org wrote:

On Tuesday, August 24, 2021 at 11:04:33 AM UTC+2 Andreas Haas wrote:

Contact emails

thib...@chromium.org, ah...@chromium.org, va...@chromium.org, ahe...@chromium.org

Explainer

https://github.com/aheejin/exception-handling

Specification

https://github.com/WebAssembly/exception-handling

Summary

This feature is adding exception support to WebAssembly. Exception handling allows code to break control flow when an exception is thrown. The exception can be any exception known by the WebAssembly module, or it may be an unknown exception that was thrown by a called imported function.

Blink component

Blink>JavaScript>WebAssembly

Search tags

wasm, webassembly, Exceptions

TAG review

Not required for WebAssembly feature launches

TAG review status

Not applicable

Risks

Interoperability and Compatibility

Gecko: Positive (https://bugzilla.mozilla.org/show_bug.cgi?id=1335652)

Looks like they shipped (or at least fully implemented), so that's definitely a strong signal :)

We have an incomplete implementation (available behind a flag in Nightly, not on by default even there) and have not in any sense shipped anything.  We do not (to my knowledge) have any publicly stated position on this spec, apart from that bug and an intent-to-prototype.

Apologies. I read too much into the issue marked as FIXED. 

[Chris Harrelson]

Hi, two points:

* This proposal appears to be only at phase 3, which is one lower than the "intent-is-rubber-stamped" level. If you wish to ship now, please provide signals from the other implementations.

* Implementation signals must come from bit.ly/blink-signals.

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[Adam Klein]

Thanks Chris. Here's the updated signals links (no replies yet on either):

* WebKit: https://lists.webkit.org/pipermail/webkit-dev/2021-August/031958.html

* Gecko: https://github.com/mozilla/standards-positions/issues/573

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[Andreas Haas]

The signals from the other implementations are in now and are both positive, see

* WebKit: https://lists.webkit.org/pipermail/webkit-dev/2021-August/031958.html

* Gecko: https://github.com/mozilla/standards-positions/issues/573

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[Chris Harrelson]

Great!

LGTM1

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAELSTve34mMRwax9sGCBXe604zkiPJAUmXHJ8bB0J-_5oLDWyg%40mail.gmail.com.

[Yoav Weiss]

LGTM2

[Andreas Haas]

Sorry for the wrong WebKit link. Here is the correct link:

https://lists.webkit.org/pipermail/webkit-dev/2021-August/031973.html

[Mike West]

LGTM3.

-mike

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAELSTvctZjb3LN6JbHuV_4K29r8Mc7xy%3DC6YR_DCJC1KTmh0QA%40mail.gmail.com.

[Alex Russell]

Non-voting note: there's no WASM exception to filing for TAG review. It should not have been skipped (as an FYI, at least) in this case.

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[Alex Russell]

Sorry for the noise; Chris Harrelson corrected me that this is fully internal to the language and doesn't have a DOM visible effect, so *is* subsumed by our JS internals exception for TAG filing.