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Parse Exception with Block Type But WABT Successfully Parses It #5951

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Parse Exception with Block Type But WABT Successfully Parses It#5951

Description

@mobsceneZ
mobsceneZ
opened on Sep 18, 2023

Hello there, I recently came across a Wasm module which cannot be parsed by Binaryen:

$ wabt/bin/wasm2wat test.wasm
(module
  (type (;0;) (func (result i32)))
  (type (;1;) (func (param i32) (result i32)))
  (func (;0;) (type 0) (result i32)
    i32.const 1
    block (param i32) (result i32)  ;; label = @1
      i32.const 2
      i32.add
    end)
  (export "param" (func 0)))

When using wasm-dis to parse above wasm module, it encountered following errors:

$ wasm-dis test.wasm
[parse exception: Block requires more values than are available (at 0:48)]
Fatal: error parsing wasm (try --debug for more info)

However, when using wasm2wat provided by WABT, it parsed successfully and wasm-interp runs param function without error:

$ wasm-interp test.wasm -r "param"
param() => i32:3

The binaryen version I tested is 16a5993, which is currently the newest commit version.

Activity

  1. redianthus commented on Sep 18, 2023

    @redianthus
    redianthus
    on Sep 18, 2023

    FYI this is accepted by the reference interpreter and by Owi.

  2. kripken commented on Sep 18, 2023

    @kripken
    kripken
    on Sep 18, 2023
    Member

    The issue is probably the same as in #5950 - Binaryen does not support multivalue input params to control flow structures (here, block (param i32)). Unfortunately it seems we don't have an error on this atm.

  3. mobsceneZ commented on Sep 19, 2023

    @mobsceneZ
    mobsceneZ
    on Sep 19, 2023
    ContributorAuthor

    The issue is probably the same as in #5950 - Binaryen does not support multivalue input params to control flow structures (here, block (param i32)). Unfortunately it seems we don't have an error on this atm.

    Thanks for your kind response, kripken. Sorry to bother but I have two more questions that I'm not sure:

    1. Does Binaryen not support table.init, elem.drop, table.copy, table.fill yet? Because I witnessed similar parse errors when dealing with these instructions.
    2. The following wat file works just fine with WABT's wat2wasm and wasm2wat, however, when I convert it into wasm binary form using wat2wasm and later use wasm-dis to parse it, error occurs:
    $ cat test.wat
(module
        (type (;0;) (func))
        (func (;0;) (type 0))
        (func (;1;) (type 0))
        (table (;0;) 10 funcref)
        (elem (;53;) declare func)
        (elem (;54;) declare funcref (ref.func 0) (ref.func 0) (ref.null func) (ref.func 1))
        (elem (;55;) declare func)
        (elem (;56;) declare func 0 0 1 1)
        (elem (;57;) declare func)
        (elem (;58;) declare funcref (ref.func 0) (ref.func 0) (ref.null func) (ref.func 1))
        (elem (;59;) declare func)
        (elem (;60;) declare func 0 0 1 1)
)
$ wat2wasm test.wat -o test.wasm
$ wasm-dis test.wasm --debug
<==
getInt8: 208 (at 40)
getInt8: 112 (at 41)
getU32LEB: 14416 ==>
== processExpressions
zz recurse into 1 at 42
getInt8: 11 (at 42)
readExpression seeing 11
zz recurse from 1 at 43
== processExpressions finished
[parse exception: expected to read a single expression (at 0:43)]
Fatal: error parsing wasm. here is what we read up to the error:
(module
 (table $0 10 funcref)
)

    It seems there is something wrong with second declarative element and parsing has a error near ref.null func, why?

  4. kripken commented on Sep 19, 2023

    @kripken
    kripken
    on Sep 19, 2023
    Member

    Does Binaryen not support table.init, elem.drop, table.copy, table.fill yet? Because I witnessed similar parse errors when dealing with these instructions.

    @tlively just implemented table.fill: #5949 Those others might not be implemented yet, but it sounds like you need them?

    I'm not sure what's going on with that elem issue, but perhaps that's a recent change to the binary format? cc @tlively

  5. tlively commented on Sep 19, 2023

    @tlively
    tlively
    on Sep 19, 2023
    Member

    Could be that we don't yet implement table initializers: #5628

  6. mobsceneZ commented on Sep 20, 2023

    @mobsceneZ
    mobsceneZ
    on Sep 20, 2023
    ContributorAuthor

    Does Binaryen not support table.init, elem.drop, table.copy, table.fill yet? Because I witnessed similar parse errors when dealing with these instructions.

    @tlively just implemented table.fill: #5949 Those others might not be implemented yet, but it sounds like you need them?

    I'm not sure what's going on with that elem issue, but perhaps that's a recent change to the binary format? cc @tlively

    Thanks again, kripken. Actually the above examples are extracted from WebAssembly's Core Specification TestSuites and I just want to use them as the seed corpus for fuzzing. So it's not a big deal if Binaryen currently doesn't support some of the instructions since I can remove related modules. :)

    Could be that we don't yet implement table initializers: #5628

    Hey tlively, thanks for your response, I'm wondering why it's related to table initializers since the parse error doesn't give me much information, is it convenient for you to explain it again?

  7. tlively commented on Sep 20, 2023

    @tlively
    tlively
    on Sep 20, 2023
    Member

    Hmm, I guess you're right that the error isn't related to table initializers since that example doesn't have any table initializers, but it seems that we're similarly missing support for something to do with element segments. Clearly our support is very patchy in this area.

    I hope that soon we will be able to run the full upstream spec test suite in Binaryen, which will help uncover this kind of bug.

  8. mobsceneZ commented on Sep 20, 2023

    @mobsceneZ
    mobsceneZ
    on Sep 20, 2023
    ContributorAuthor

    Hmm, I guess you're right that the error isn't related to table initializers since that example doesn't have any table initializers, but it seems that we're similarly missing support for something to do with element segments. Clearly our support is very patchy in this area.

    I hope that soon we will be able to run the full upstream spec test suite in Binaryen, which will help uncover this kind of bug.

    Thanks for your kind reply and hope Binaryen would get better in the future :)

  9. kripken commented on Nov 2, 2023

    @kripken
    kripken
    on Nov 2, 2023
    Member

    Table.copy is added in #6078

  10. kripken
    added a commit that references this issue on Nov 6, 2023

    Implement table.copy (#6078)

    e3d2716
  11. radekdoulik
    added a commit that references this issue on Jul 12, 2024

    Implement table.copy (WebAssembly#6078)

    c246150

  12. kripken commented on Aug 8, 2024

    @kripken
    kripken
    on Aug 8, 2024
    Member

    table.init is added in #6827

  13. tlively commented on Jan 11, 2025

    @tlively
    tlively
    on Jan 11, 2025
    Member

    We now support parsing block parameters, so the original issue here is solved. The only bulk table instruction we still don't support is elem.drop, but I filed a dedicated issue to track that here: #7209.

  14. tlively
    closed this as completedon Jan 11, 2025
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