wasi-print: : implementation of Rust print macros and similar for no_std WASI

Bart Massey 2023 (version 0.2.1)

This crate contains basic niceties for writing no_std modules for WASI. wasi-print provides:

• An abort() function that raises a WASI exception.
• A panic_handler that aborts after trying to print panic information.
• A print_fd() function that prints an &str to a WASI fd.
• Printing macros print!(), println!(), !eprint() and !eprintln().

Example

This is a full standalone Rust WASM program using wasi_print.

```rust

![no_std]

use wasi_print::*;

[no_mangle]

pub extern "C" fn mathadd(x: i32, y: i32) -> i32 { eprint!("guest running mathadd({}, {}) …", x, y); let result = x + y; eprintln!(" and returning {}", result); result } ```

Features

• print: Include printing code. This requires nightly for a variety of reasons.
• panic_handler: Provide a panic handler.

Notes

When used without the print feature, this crate can be built on stable Rust.

Acknowledgments

Figuring out how to write this was made much easier by this excellent blog post by "James [Undefined]".

License

This work is licensed under the "MIT License". Please see the file LICENSE.txt in this distribution for license terms.

Further Acknowledgments

Thanks to the cargo-readme crate for generation of this README.