Errors while executing hello world example with lucetc-wasi

[sergiizubchevskyy]

Hello!

I've installed Lucet by following documentation here: https://bytecodealliance.github.io/lucet/Compiling-on-Linux.html, and opted for the first installation method.

After that I compiled hello world example using steps described here: https://bytecodealliance.github.io/lucet/Your-first-Lucet-application.html

After compiling hello.wasm file I execute it with Wasmtime (v 0.19.0) and it prints "Hello World" as expected.

However after generating hello.so file and attempting to execute it with lucetc-wasi command I'm getting errors like: unexpected char, unexpected EOF, unexpected token etc.

Example:
1:

2:

3:

Also, I might be going the wrong path here but I'm attempting to use Lucet to produce some sort of AOT file that will skip the compilation performed by Wasmtime. I assumed that Wasmtime should be able to consume hello.so, however this is not the case, it outputs the following:

Could you point me in the right directions here? Am I understanding correctly the Lucet's usage?

Thank you in advance.

[jedisct1]

Hi!

lucetc-wasi is the compiler. It cannot run code.

The resulting .so (or .dylib) file must be run with lucet-wasi, which is a different tool.

[sergiizubchevskyy]

Wow! Thank you for such a fast answer! I'm reinstalling the Lucet so will try as soon as it is installed.

And what about the Wasmtime? Is there a way to pass compiled .so object or similar to avoid compilation by JIT compiler of Wasmtime?

[sergiizubchevskyy]

You're correct, invoking the lucet-wasi tool solves the issue with errors.

From what I read in the meantime, I've got an impression that there is no way (at least for now) to use some sort of AOT with the Wasmtime, and I had am impression that Wasmtime is the runtime used by Lucet but after searching I think Wasmtime is used to provide some files for build support.

[jedisct1]

Wasmtime includes a cache: https://bytecodealliance.github.io/wasmtime/cli-cache.html - Once code has been cached, it doesn’t need to be recompiled any more.

[sergiizubchevskyy]

Thank you!

I've done some tests and according to Valgrind Massif and got a bit surprised since consecutive executions with cache enabled still got almost 4MiB, when comparing with Wasmtime JIT (cache disabled) 4.4MiB... It is improvement, but not as much as I was expecting.

Check this out:
1st cache enabled execution:

2nd cache enabled execution:

3rd cache enabled execution:

And now Wasmtime, cache disabled:

But this is way beyond Lucet's responsibility!

Thank you again jedisct1! You really helped me a lot.

I think this issue can be closed, you prefer me to close it?