Compilation failed ?

[orangeC23]

Steps to reproduce

(1) cargo new testfile
(2) cd testfile
Modify the main.rs :

use std::fs::File;
use std::os::unix::io::AsRawFd;

fn main() {
    let file = File::open("./hello.txt").expect("Can not open.");
    let file_descriptor = file.as_raw_fd();
    println!("File descriptor {}", file_descriptor);

}

And create file hello.txt.

(3) execute cargo run , it prints:

File descriptor 3

(4) However, when execute 'cargo build --target wasm32-wasi', it prints

[pchickey]

This issue has to do with Rust std, not wasmtime. The std::os::unix module is not available when targeting wasi, because wasi is not a unix. There is no equivalent of AsRawFd for that target.

What are your needs for AsRawFd under wasi?

[sunfishcode]

Rust std recently add a new feature, the std::os::fd module, which abstracts over unix and wasi, and contains an AsRawFd which works on both WASI and Unix.

So if you write your program like this:

use std::fs::File;
use std::os::fd::AsRawFd;

fn main() {
    let file = File::open("./hello.txt").expect("Can not open.");
    let file_descriptor = file.as_raw_fd();
    println!("File descriptor {}", file_descriptor);

}

It compiles under both Unix and WASI.

[orangeC23]

Thanks a lot ! Now it works !