[Cross-Platform Bug] macOS build fails

[0xEgao]

Currently it compiles and runs successfully on Linux, but fails on macOS with the following error:
*mut c_void cannot be sent between threads safely

Root cause

On macOS, mio (or kqueue-based poll registry) uses raw pointers (*mut c_void) internally, which are not Send,therefore it doesn't compiles.

[hulxv]

Can you share build error messages please?

[0xEgao]

Can you share build error messages please?

*mut c_void` cannot be sent between threads safely
    --> src/reactor.rs:73:24
     |
  73 |           self.pool.exec(move || {
     |                     ---- ^------
     |                     |    |
     |  ___________________|____within this `{closure@src/reactor.rs:73:24: 73:31}`
     | |                   |
     | |                   required by a bound introduced by this call
  74 | |             let entry = registry.get(&token);
  75 | |
  76 | |             if let Some(entry) = entry {
...    |
  85 | |         })
     | |_________^ `*mut c_void` cannot be sent between threads safely
     |
     = help: within `{closure@src/reactor.rs:73:24: 73:31}`, the trait `Send` is not implemented for `*mut c_void`
note: required because it appears within the type `libc::unix::bsd::apple::kevent`
    --> /Users/0xegao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/libc-0.2.177/src/unix/bsd/apple/mod.rs:1322:16
     |
1322 |     pub struct kevent {
     |                ^^^^^^
note: required because it appears within the type `Event`
    --> /Users/0xegao/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/mio-1.0.4/src/event/event.rs:17:12
     |
  17 | pub struct Event {
     |            ^^^^^
note: required because it's used within this closure
    --> src/reactor.rs:73:24
     |
  73 |         self.pool.exec(move || {
     |                        ^^^^^^^
note: required by a bound in `ThreadPool::exec`
    --> src/thread_pool.rs:49:23
     |
  47 |     pub fn exec<F>(&self, task: F) -> Result<()>
     |            ---- required by a bound in this associated function
  48 |     where
  49 |         F: FnOnce() + Send + 'static,
     |                       ^^^^ required by this bound in `ThreadPool::exec`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `mill-io` (lib) due to 1 previous error