Wasmcraft

Have you ever wanted to run C/C++/Rust/WebAssembly applications in Minecraft? No? Well, now you can!

Wasmcraft is a compiler from WebAssembly to Minecraft Java Edition datapacks. Since WebAssembly is a well-supported target for many languages, this means that you can run code written in e.g. C in Minecraft.

This was inspired by Sethbling's Atari 2600 Datapack and is the (much, much improved) spiritual successor to Langcraft.

Demonstration

Here is a short demonstration of a port of Minecraft 4k, compiled using wasmcraft, running in vanilla Minecraft. (That's right: Minecraft in Minecraft).

Alternatively, here is a video of the CHIP-8 Emulator from here running Pong.

Features

All integer operations supported
(Relatively) efficient code generation
Works most of the time

Usage

Let's say we want to run the following program:

/* foo.c */

#include "mcinterface.h"

// Since there is no standard library, we use `_start` instead of `main`
int _start() {
	for (int i = 0; i < 10; ++i) {
		print(i);
	}

	return 0;
}

First, compile it to WebAssembly:

clang foo.c -target wasm32 -nostdlib -o foo.wasm

Ensure you have Rust version >= 1.58 installed, which is very recent. To update Rust, run rustup update. Then, simply navigate to the wasmcraft2 directory and run:

cargo run --release -- ../foo.wasm ../nameofdatapack

This will create a datapack in the folder nameofdatapack, which can be directly placed in the datapacks folder of any Minecraft Java Edition world (this has only been tested on 1.18, but should work on older versions as well).

Note that due to limitations with Minecraft commands, this needs to fill a few chunks near 0, 0 with jukeboxes, so do NOT run this in a world with builds you don't want destroyed!

Run these commands:

/gamerule maxCommandChainLength 1000000 (This only needs to be run once per world)

/reload (This only needs to be run when the datapack is changed while the world is open)

/function wasmrunner:init

/function wasmrunner:_start

And you should see the numbers 0 to 9 printed out in the chat.

Limitations

Floating point operations are not supported (yet). Use fixed point operations instead, e.g. libfixmath
Bitwise operations and 64-bit divisions are absurdly slow.
8-bit and 16-bit accesses are fairly slow, and all memory accesses have not-insignificant overhead.
Manual calls to sleep() have to be inserted in long-running code, because Minecraft can only run a limited number of commands per tick.
The API is very limited

License

Licensed under either of

MIT License
Apache License, Version 2.0

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Comments

does not compile under linux

wasmcraft2, the thing itself does not compile on my machine. here's a rather meaningless, but kinda long error stack:

   Compiling wasmcraft v0.1.0 (/mnt/dev/wasmcraft2)
error[E0432]: unresolved import `datapack_common::functions::command_components::Uuid`
 --> src/pack_emitter/mod.rs:4:89
  |
4 | use datapack_common::functions::{Function, Command, command_components::{FunctionIdent, Uuid, SNbt}};
  |                                                                                         ^^^^ no `Uuid` in `functions::command_components`

warning: unused import: `SimpleLivenessInfo`
 --> src/ssa/lir_emitter.rs:7:101
  |
7 | use super::{SsaProgram, SsaFunction, SsaBasicBlock, BlockId, reg_alloc::*, liveness::{LivenessInfo, SimpleLivenessInfo}, call_graph::Call...
  |                                                                                                     ^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` on by default

warning: unused import: `ssa::liveness::print_live_ranges`
 --> src/ssa/reg_alloc.rs:3:46
  |
3 | use crate::{lir::{Register, DoubleRegister}, ssa::liveness::print_live_ranges};
  |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

warning: unreachable statement
    --> src/pack_emitter/mod.rs:1507:2
     |
1504 |       return;
     |       ------ any code following this expression is unreachable
...
1507 | /     if dst != lhs {
1508 | |         code.push(format!("scoreboard players operation {dst} = {lhs}"));
1509 | |     }
     | |_____^ unreachable statement
     |
     = note: `#[warn(unreachable_code)]` on by default

error[E0616]: field `call_stack` of struct `Interpreter` is private
   --> src/lib.rs:343:31
    |
343 |         if let Some(frame) = interp.call_stack.iter().rev().next() {
    |                                     ^^^^^^^^^^ private field
    |
help: a method `call_stack` also exists, call it with parentheses
    |
343 |         if let Some(frame) = interp.call_stack().iter().rev().next() {
    |                                               ++

error[E0609]: no field `func` on type `&(usize, usize)`
   --> src/lib.rs:344:21
    |
344 |             indiv_time[frame.func] += 1;
    |                              ^^^^

error[E0616]: field `call_stack` of struct `Interpreter` is private
   --> src/lib.rs:347:23
    |
347 |         for frame in interp.call_stack.iter().rev() {
    |                             ^^^^^^^^^^ private field
    |
help: a method `call_stack` also exists, call it with parentheses
    |
347 |         for frame in interp.call_stack().iter().rev() {
    |                                       ++

error[E0609]: no field `func` on type `&(usize, usize)`
   --> src/lib.rs:348:29
    |
348 |             if !intrin_visited[frame.func] {
    |                                      ^^^^

error[E0609]: no field `func` on type `&(usize, usize)`
   --> src/lib.rs:349:26
    |
349 |                 intrin_visited[frame.func] = true;
    |                                      ^^^^

error[E0609]: no field `func` on type `&(usize, usize)`
   --> src/lib.rs:350:28
    |
350 |                 intrin_cum_times[frame.func] += 1;
    |                                        ^^^^

error[E0609]: no field `func` on type `&(usize, usize)`
   --> src/lib.rs:353:27
    |
353 |             if !intrin_funcs[frame.func] {
    |                                    ^^^^

Some errors have detailed explanations: E0432, E0609, E0616.
For more information about an error, try `rustc --explain E0432`.
warning: `wasmcraft` (lib) generated 3 warnings
error: could not compile `wasmcraft` due to 8 previous errors; 3 warnings emitted
warning: build failed, waiting for other jobs to finish...

opened by manen 4