AS generates invalid .wast

[carllocos]

I wrote an AssemnlyScript application (see mirror-led.ts and config.ts in zip) that cannot be compiled to wasm. In particular, wat2wasm fails to compile the obtained wast file to wasm due to several type errors. Some of the errors that I get are:upload.wast:612:6: error: type mismatch in if true branch, expected [i32] but got [], and upload.wast:7658:4: error: type mismatch at end of function, expected [] but got [i32, i32]. All the files generated by asc can be found in the directory output of the zip.

This compilation issue comes as a surprise because the asc generates alongside the Wast file also a wasm file indicating that no type error occurred in the process. So this may mean that our wat2wasm is behind some language features.

This type error issue only manifest when compiling via asc without any optimisation. Since we also want to debug without optimisation I will have to further investigate this issue.

src_files.zip

[tolauwae]

It works on my machine with AssemblyScript 0.27.5. I used the template and ran:

npm install
npm run build
wat2wasm bin/main.debug.wast --no-canonicalize-leb128s --disable-bulk-memory -v

[carllocos]

@tolauwae did you also use no optimisation? (i.e., remove the -O3s from the asc command) because I also have version 0.27.5 and with optimisation the wasm gets generated but without optimisation, I get the type error.

[tolauwae]

I used the debug profile of the template which doesn't optimize. And it works. What is your exact asc command?

[carllocos]

@tolauwae

full command

 asc path/to/src.ts --exportTable --disable bulk-memory --sourceMap --debug --outFile tmp/upload.wasm --textFile tmp/upload.wast`

Something crucial I forgot to mention
The type error occurring here above may occur unbeknownst to the user. For some reason, the plugin does not automatically stop even if the wat2wasm fails and thus proceeds with the next step i.e., flashing the upload.wasm to the MCU. Surprisingly this will succeed and the reason is that the plugin will search for a tmp/upload.wasm to flash which will be present in the tmp/ directory. This is because asc also generated besides the wast file a upload.wasm file that is put in the tmp/ dir. In other words, from the user perspective flashing will be successful since the wasm of asc is used. The only way I noticed the wat2wasm failure is by putting a breakpoint on this line. The stderror contained the type errors that I showed here above.

I also tried to use the template since it may not have the compilation error but I fail to properly configure it. Can you please confirm whether the following steps are correct:

• run npm install and npm run build in the root directory of the template
• add a .vscode/launch.json file into the root directory of the template
• change the program key of launch.json to point to the main.ts of the template
• replace this line of the plugin with const command = `cd ${path.dirname(this.sourceFilePath.toString())} ; asc ${this.sourceFilePath} --config asconfig.json --target debug`; so that asc uses the config of the template

[tolauwae]

There is no need to recompile with wat2wasm. I haven't checked if there is a size difference, but I don't imagine the wasm from asc is larger than the wasm from wat2wasm.

[tolauwae]

Compiled file with your command also works for me.

[tolauwae]

I also tried to use the template since it may not have the compilation error but I fail to properly configure it. Can you please confirm whether the following steps are correct:

Quickly tried it myself and AS doesn't seem to work right now in the plugin. Don't know what broke.

replace this line of the plugin with const command = cd ${path.dirname(this.sourceFilePath.toString())} ; asc ${this.sourceFilePath} --config asconfig.json --target debug; so that asc uses the config of the template

You don't have to change this. It should work regardless, but doesn't strangely. I tried it without changing any code on the main branch.

[tolauwae]

It wasn't working on my machine because the plugin used the globally installed asc instead of the local. #122 fixes this.

[tolauwae]

In other words, I still can't replicate your issue. The wast2wasm can compile the .wast generated by AS.

[tolauwae]

Nevermind. I must not have run it exactly the same. I get the error now as well.

[carllocos]

So I found the problem, the asc compiler was missing the --runtime stub option.

To be honest I do not see immediately how that option relates to valid wast, especially because the invalid wast type was already previously reported and fixed by the maintainers of asc (see AssemblyScript/assemblyscript#310).

I will push my fix as part of this PR #122. However, I now encountered another problem for which I still need to create a new issue (depending on the answer to this comment TOPLLab/WARDuino#197 (comment)) and for which the fix maybe should be included also in the same PR.