A terminal pane that closes takes its shell and pty with it, in every front end

The detached server closed a pane's pty only when the shell was respawned,
hit EOF or the session shut down, so rmdir, Del or Delcol on a terminal
left its shell running with nobody to read it; the tty front end and
macOS did the same. Retiring a terminal pane now emits a close_pty
effect, which each host that runs shells answers by hanging the pty up
and ending the shell (the detached server's and the GUI's existing
retire-and-reap path, and a close plus SIGHUP in the tty and macOS
shells).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/tty/tty.zig b/src/tty/tty.zig
index 903c5c0c..b2768ed6 100644
--- a/src/tty/tty.zig
+++ b/src/tty/tty.zig
@@ -924,6 +924,7 @@ const Shell = struct {
         .pty_write = ptyWrite,
         .pty_resize = ptyResize,
         .pty_signal = ptySignal,
+        .close_pty = closePty,
         .tty_taken = ttyTaken,
         .write_file = writeFile,
         .write_dump = writeDump,
@@ -1227,6 +1228,20 @@ const Shell = struct {
         if (s.ptys[pane]) |pt| host_io.signalTty(pt.pid, pt.file.handle, sig);
     }
 
+    /// The pane is gone: hang its pty up, which the kernel passes on to the
+    /// shell as SIGHUP, and say it too for a shell that ignores the tty's.
+    /// Output still in flight carries the old generation and is dropped.
+    fn closePty(ctx: ?*anyopaque, pane: u8) void {
+        const s = of(ctx);
+        var pt = s.ptys[pane] orelse return;
+        s.ptys[pane] = null;
+        s.gens[pane] +%= 1;
+        pt.reader.cancel(s.io) catch {};
+        _ = libc.close(pt.file.handle);
+        _ = libc.kill(pt.pid, posix.SIG.HUP);
+        _ = libc.waitpid(pt.pid, null, posix.W.NOHANG);
+    }
+
     fn ttyTaken(ctx: ?*anyopaque, pane: u8) bool {
         const s = of(ctx);
         const pt = s.ptys[pane] orelse return false;