fix(process): safely exit forked child after spawn

Co-Authored-By: Michael Murphy <michael@mmurphy.dev>

src/process.rs

@@ -5,7 +5,7 @@
 use smol::io::AsyncReadExt;
 use std::io;
 use std::os::fd::OwnedFd;
-use std::process::{Command, Stdio, exit};
+use std::process::{Command, Stdio};
 #[cfg(feature = "tokio")]
 use tokio::io::AsyncReadExt;
 
@@ -56,24 +56,33 @@ pub async fn spawn(mut command: Command) -> Option<u32> {
 
     match unsafe { libc::fork() } {
         // Parent process
-        1.. => {
+        fork_pid @ 1..=i32::MAX => {
             // Drop copy of write end, then read PID from pipe
             drop(write);
             let pid = read_from_pipe(read).await;
-            // wait to prevent zombie
-            _ = rustix::process::wait(rustix::process::WaitOptions::empty());
+            _ = rustix::process::waitpid(
+                rustix::process::Pid::from_raw(fork_pid),
+                rustix::process::WaitOptions::empty(),
+            );
             pid
         }
 
         // Child process
         0 => {
             let _res = rustix::process::setsid();
-            if let Ok(child) = command.spawn() {
+            let exit_status = if let Ok(child) = command.spawn() {
                 // Write PID to pipe
                 let _ = rustix::io::write(write, &child.id().to_be_bytes());
-            }
+                0
+            } else {
+                1
+            };
 
-            exit(0)
+            // # Safety
+            // Required for child fork to exit without affecting the parent.
+            unsafe {
+                libc::_exit(exit_status);
+            }
         }
 
         ..=-1 => {