StackOverflow error in scodec lazily

[Jacarte]

Hi @satabin

I was trying to decode/encode a large WASM module (here you can find it).

When I try to decode the binary swam launches a StackOverflow in this location

swam/core/src/swam/binary/InstCodec.scala

Line 96 in fd76cb9

case OpCode.Block => block.decode(remainder).map(_.map(Block))

,

swam/core/src/swam/binary/InstCodec.scala

Line 444 in fd76cb9

.encode(tpe ~ insts)

and here

swam/core/src/swam/binary/InstCodec.scala

Line 35 in fd76cb9

blockType ~ lazily(expr)

. It seems to be an issue with the lazily option of scodec and the size of the recursion.

Any idea?

Thanks in advancne

[satabin]

I can't figure out what I could do in this case. Does the wasm file has deeply nested blocks? I wanted to rewrite the binary parser to not use this library anymore, this could be a good opportunity.

[Jacarte]

Hi Lucas,

If you plan to do so, maybe is a good idea to add the extra wasm sections in the engine. Take a look at https://github.com/v8/v8/blob/4b9b23521e6fd42373ebbcb20ebe03bf445494f9/src/wasm/wasm-constants.h#L74 . I was trying to play with the ffmpeg wasm file and it seems to have extra, non-custom sections,12 and 13. I tried to parse it with wabt and wasabi and they are not implementing this parsing. Have you read about these sections?

I will open a new issue on this

[satabin]

I didn't read about these sections yet, I just followed what is specified so far. I will have a look.

[Jacarte]

It seems to be the bulk memory operation feature, https://github.com/WebAssembly/bulk-memory-operations/blob/master/proposals/bulk-memory-operations/Overview.md. Here is the roadmap defined in the official site https://webassembly.org/roadmap/