Update JS API for exnref #301
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@@ -101,6 +101,7 @@ urlPrefix: https://webassembly.github.io/exception-handling/core/; spec: WebAsse | |
| text: memory address; url: exec/runtime.html#syntax-memaddr | ||
| text: global address; url: exec/runtime.html#syntax-globaladdr | ||
| text: extern address; url: exec/runtime.html#syntax-externaddr | ||
| text: tag type; url: syntax/types.html#syntax-tagtype | ||
| text: tag address; url: exec/runtime.html#syntax-tagaddr | ||
| text: tag_alloc; url: appendix/embedding.html#embed-tag-alloc | ||
| text: tag_type; url: appendix/embedding.html#embed-tag-type | ||
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@@ -1080,20 +1081,18 @@ Note: Exported Functions do not have a \[[Construct]] method and thus it is not | |
| 1. [=Clean up after running a callback=] with |stored settings|. | ||
| 1. [=Clean up after running script=] with |relevant settings|. | ||
| 1. Assert: |result|.\[[Type]] is <emu-const>throw</emu-const> or <emu-const>normal</emu-const>. | ||
| 1. Let |store| be the [=surrounding agent=]'s [=associated store=]. | ||
| 1. If |result|.\[[Type]] is <emu-const>throw</emu-const>, then: | ||
| 1. Let |v| be |result|.\[[Value]]. | ||
| 1. If |v| [=implements=] {{Exception}}, | ||
| 1. Let |address| be |v|.\[[Address]]. | ||
| 1. Otherwise, | ||
| 1. Let |type| be the result of [=get the JavaScript exception tag |getting the JavaScript exception tag=]. | ||
| 1. Let |payload| be [=!=] [=ToWebAssemblyValue=](|v|, [=externref=]). | ||
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There was a problem hiding this comment. It looks There was a problem hiding this comment. The ... actually though, I just noticed that the handling of completion records between 'run a host function' and 'create a host function' wasn't quite right even before the EH spec. I just filed WebAssembly/spec#1743 about that. |
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| 1. Let (|store|, |address|) be [=exn_alloc=](|store|, |type|, « |payload| »). | ||
| 1. Set the [=surrounding agent=]'s [=associated store=] to |store|. | ||
| 1. [=WebAssembly/Throw=] with |address|. | ||
| 1. Otherwise, return |result|.\[[Value]]. | ||
| 1. Let (|store|, |funcaddr|) be [=func_alloc=](|store|, |functype|, |hostfunc|). | ||
| 1. Set the [=surrounding agent=]'s [=associated store=] to |store|. | ||
| 1. Return |funcaddr|. | ||
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@@ -1312,7 +1311,7 @@ constructor steps are: | |
| 1. Throw a {{TypeError}}. | ||
| 1. Let |wasmPayload| be « ». | ||
| 1. [=list/iterate|For each=] |value| and |resultType| of |payload| and |types|, paired linearly, | ||
| 1. [=list/Append=] [=?=] [=ToWebAssemblyValue=](|value|, |resultType|) to |wasmPayload|. | ||
| 1. Let (|store|, |exceptionAddr|) be [=exn_alloc=](|store|, |exceptionTag|.\[[Address]], |wasmPayload|) | ||
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| 1. Set the [=surrounding agent=]'s [=associated store=] to |store|. | ||
| 1. [=initialize an Exception object|Initialize=] **this** from |exceptionAddr|. | ||
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@@ -1357,7 +1356,7 @@ The <dfn attribute for="Exception">stack</dfn> getter steps are: | |
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| The <dfn>JavaScript exception tag</dfn> is a [=tag address=] associated with | ||
| the surrounding agent. It is allocated in the agent's [=associated store=] on | ||
| first use and cached. It always has the [=tag type=] « [=externref=] » → « ». | ||
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| <div algorithm> | ||
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@@ -1376,7 +1375,7 @@ To <dfn>get the JavaScript exception tag</dfn>, perform the following steps: | |
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| <div algorithm> | ||
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| To <dfn for=WebAssembly>throw</dfn> with an [=exception address=] |address|, perform the following steps: | ||
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| 1. Unwind the stack until reaching the *catching try block* given |type|. | ||
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There was a problem hiding this comment. This is the main bit that still needs to be updated, as there is currently nothing in the embedding appendix that I could find that even describes calling from wasm into the embedder, and thus nowhere to put a description of what happens when such calls throw. There was a problem hiding this comment. The problem is that this can not be an "external" function, since it could only be invoked inside a Wasm context. So it can't easily be defined as a proper embedder function, which need a closed evaluation context. To make it work, we would need to pass it the "current evaluation context", which would require means for reifying an entire host/Wasm execution. There is no way to make that work with the JS spec style. But this algorithm is invoked from another one that already describes Wasm semantics, not host semantics. So we're morally "inside Wasm". So what I'd suggest is to say something like "execute the Wasm instructions And with my other comment there is only one place left where this is invoked, so I'd just inline that step there and remove this algorithm. |
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| 1. Invoke the catch block with |payload| and |address|. | ||
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Does a
WebAssembly.Exceptionobject haveAddress?There was a problem hiding this comment.
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Yes,
Addressis initialized in "initialize an Exception object". Exception is now just like all the other JS-exposed objects which also have their wasm Addresses stored in an internal slot in the JS object. (Although I just noticed that the naming convention isn't consistent right now; TheExceptionandTagobjects have the address in a field namedAddresswhereas the rest have that field named after the object type, e.g.Global. Maybe I'll fix that in a followup change).