Wac: Minimal WebAssembly interpreter written in C

https://github.com/grassel/wac#wac---webassembly-in-c

by ingve • 7 years ago

111 41 7 years ago

github.com

jerrysievert• 7 years ago

not just a WASM interpreter, but one that is targeting small devices, which is pretty darned cool.

my thoughts go directly to fast over the air updates without a full flash, fixing bugs or reconfiguring on the fly.

snops• 7 years ago

For a interpreter targeted at small/embedded devices, it would be interesting to see the ROM/RAM usage.

astrodust• 7 years ago

Trial by fire: Get it on the PICO8: https://www.lexaloffle.com/pico-8.php

jamesgeck0• 7 years ago

Even if this was rewritten in Lua, I'm pretty sure that you'd have to figure out how to get it under the token limit before you had to worry about running in 512k RAM.

RodgerTheGreat• 7 years ago

PICO8 is in many ways less constrained than real-world microcontrollers, and the nature of the constraints is quite different. It simply isn't a meaningful comparison.

swiley3• 7 years ago

meh, if you really want to try it on a game console at least pick one that resembles a computer/microcontroller.

The PICO8 is very pretty but it's not at all like small 8/16 bit computers.

kevingadd• 7 years ago

Given the small scope and some of the ideal use cases for this, it would be really great to have some objectives like being 100% asan, msan, ubsan-clean and passing valgrind. People will eventually ship stuff like this in IoT and that'll make it unlikely that security and bug patches will get deployed.

daniel_rh• 7 years ago

or written in a secure language without undefined behavior and without any "unsafe" code like Rust or Safe Haskell.

IoT probably should be shipping code that uses static compiler checks as the first line of security defense rather than run-time checks like valgrind and asan.

Skunkleton• 7 years ago

Embedded programming will always be unsafe to a degree. You can't avoid interacting w/ hardware. Static analysis can only get you so far.

BubRoss2• 7 years ago

Hello World in Haskell would already be too large for many micro controllers.

swiley3• 7 years ago

Writing large C projects without tools like valgrind is crazy! I guess in some situations it can be hard to set up (like kernel programming.) but user space software should always be written with it.

My personal experience is tools like valgrind will immediately shove stupid mistakes back in your face (rather than waiting a few days to realize the change you made is corrupting the heap in a way that eventually causes the program to crash.) and the result is not only better memory management in your project but also better memory management in future projects.

redmar• 7 years ago

link gives a 404 because the repo is renamed minutes ago to https://github.com/grassel/wac-esp

donpdonp• 7 years ago

which was forked from https://github.com/kanaka/wac the kanaka project appears to be a generic platform project where as the grassel fork is targeting the esp32.

pcwalton2• 7 years ago

This line: https://github.com/grassel/wac-esp/blob/master/main/wa.c#L68...

What prevents me from writing a wasm file with an arbitrary value for "depth" greater than CALLSTACK_SIZE (1024) and overflowing the buffer? (If the answer is "nothing", that's probably arbitrary code execution.)

rcfox• 7 years ago

You should probably write this in an issue so that the developers see it.

pcwalton2• 7 years ago

It took me 10 minutes to find on my phone on the train. There are probably dozens of bugs like this...

int_19h3• 7 years ago

Is it meant to be a sandbox? I don't see anything to that effect on the GitHub page.

sitkack4• 7 years ago

When is Wasm not a sandbox?

Page one of the spec

– Safe: code is validated and executes in a memory-safe3, sandboxed environment preventing data cor-ruption or security breaches.

swiley3• 7 years ago

The URL for the original project is [1]

It's strange that the readme says it requires 32 bit userspace tools.

Part of me is pretty excited to have an open "write once run everywhere" environment but the other part of me really likes that autoconf/cmake more or less provide that now and I'm worried that things like this will discourage people from making their projects easily buildable by the end user.

Docker already does that, try building freeciv-web yourself without tools like docker, the end result is that it can be very difficult to modify it when you need to.

[1] https://github.com/kanaka/wac

jokoon2• 7 years ago

Is the gcc team/clang team working to allow wasm as a target?

I heard there are several compilers that work with c++ but i don't see many.

nestorD• 7 years ago

LLVM has a wasm target so, in theory, clang should be able yo target it without modifications . In practice I found this short guide : https://stackoverflow.com/questions/45146099/how-do-i-compil...

jokoon2• 7 years ago

This guide requires binaryen... I tried to build it once, it was not fun.

Wac: Minimal WebAssembly interpreter written in C

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