flush cause pollable to hang

[peter-jerry-ye]

Description

Flush, then poll on the stdout, will cause the program to hang.

Expected behavior

The program finishes, as wasmtime's behavior.

Steps to reproduce:

• run cargo component new flush --lib && cd flush
• update deps.toml and run wit-deps update:

  cli = "https://github.com/Webassembly/wasi-cli/archive/refs/tags/v0.2.0.tar.gz"

• update world.wit (and deps.toml) to:

  package component:flush;
  
  /// An example world for the component to target.
  world example {
      include wasi:cli/command@0.2.0;
  }

• append to Cargo.toml

  [package.metadata.component.target.dependencies]
  "wasi:random" = { path = "wit/deps/random" }
  "wasi:cli" = { path = "wit/deps/cli" }
  "wasi:io" = { path = "wit/deps/io" }
  "wasi:clocks" = { path = "wit/deps/clocks" }
  "wasi:filesystem" = { path = "wit/deps/filesystem" }
  "wasi:sockets" = { path = "wit/deps/sockets" }

• Modify src/lib.rs

  #[allow(warnings)]
  mod bindings;
  
  use bindings::wasi;
  
  use crate::bindings::exports::wasi::cli::run::Guest;
  
  struct Component;
  
  impl Guest for Component {
      fn run() -> Result<(), ()> {
          let stdout = wasi::cli::stdout::get_stdout();
          stdout.flush().unwrap();
          let poll = stdout.subscribe();
          poll.block();
          Ok(())
      }
  }
  
  bindings::export!(Component with_types_in bindings);

• run cargo component build
• run wasmtime run target/wasm32-wasip1/debug/flush.wasm and jco run target/wasm32-wasip1/debug/flush.wasm

[vados-cosmonic]

Hey @peter-jerry-ye a bit late here, but thanks for reporting this -- will try to build it & reproduce.