Fix FD leak after closing child windows

This patch fixes an issue with signal handling where Alacritty would
permanently create one signal handling FD for each alacritty window
created by an instance. This FD was never released, causing a leak of
the FD.

Closes #7983.

1 files changed, 11 insertions, 6 deletions

diff --git a/alacritty_terminal/src/tty/unix.rs b/alacritty_terminal/src/tty/unix.rs
index 1336fd04..1a2104c6 100644
--- a/alacritty_terminal/src/tty/unix.rs
+++ b/alacritty_terminal/src/tty/unix.rs
@@ -19,8 +19,8 @@ use rustix_openpty::openpty;
 use rustix_openpty::rustix::termios::Winsize;
 #[cfg(any(target_os = "linux", target_os = "macos"))]
 use rustix_openpty::rustix::termios::{self, InputModes, OptionalActions};
-use signal_hook::consts as sigconsts;
-use signal_hook::low_level::pipe as signal_pipe;
+use signal_hook::low_level::{pipe as signal_pipe, unregister as unregister_signal};
+use signal_hook::{consts as sigconsts, SigId};
 
 use crate::event::{OnResize, WindowSize};
 use crate::tty::{ChildEvent, EventedPty, EventedReadWrite, Options};
@@ -102,6 +102,7 @@ pub struct Pty {
     child: Child,
     file: File,
     signals: UnixStream,
+    sig_id: SigId,
 }
 
 impl Pty {
@@ -260,13 +261,13 @@ pub fn from_fd(config: &Options, window_id: u64, master: OwnedFd, slave: OwnedFd
     }
 
     // Prepare signal handling before spawning child.
-    let signals = {
+    let (signals, sig_id) = {
         let (sender, recv) = UnixStream::pair()?;
 
         // Register the recv end of the pipe for SIGCHLD.
-        signal_pipe::register(sigconsts::SIGCHLD, sender)?;
+        let sig_id = signal_pipe::register(sigconsts::SIGCHLD, sender)?;
         recv.set_nonblocking(true)?;
-        recv
+        (recv, sig_id)
     };
 
     match builder.spawn() {
@@ -277,7 +278,7 @@ pub fn from_fd(config: &Options, window_id: u64, master: OwnedFd, slave: OwnedFd
                 set_nonblocking(master_fd);
             }
 
-            Ok(Pty { child, file: File::from(master), signals })
+            Ok(Pty { child, file: File::from(master), signals, sig_id })
         },
         Err(err) => Err(Error::new(
             err.kind(),
@@ -296,6 +297,10 @@ impl Drop for Pty {
         unsafe {
             libc::kill(self.child.id() as i32, libc::SIGHUP);
         }
+
+        // Clear signal-hook handler.
+        unregister_signal(self.sig_id);
+
         let _ = self.child.wait();
     }
 }