Fix shutdown deadlock

Calling ::std::process::exit() from the SIGCHLD handler would sometimes
deadlock some OpenGL internal shutdown procedure. To resolve this, a
flag was added that can be checked with `process_should_exit`.

src/main.rs

@@ -44,6 +44,7 @@ use grid::Grid;
 use term::Term;
 use meter::Meter;
 use util::thread;
+use tty::process_should_exit;
 
 #[derive(Debug, Eq, PartialEq, Copy, Clone, Default)]
 pub struct Rgb {
@@ -130,7 +131,7 @@ fn main() {
     }
 
     let (chars_tx, chars_rx) = ::std::sync::mpsc::channel();
-    thread::spawn_named("TTY Reader", move || {
+    let reader_thread = thread::spawn_named("TTY Reader", move || {
         for c in reader.chars() {
             let c = c.unwrap();
             chars_tx.send(c).unwrap();
@@ -219,8 +220,13 @@ fn main() {
 
             window.swap_buffers().unwrap();
         }
+
+        if process_should_exit() {
+            break;
+        }
     }
 
-    // TODO handle child cleanup
+    reader_thread.join();
+    println!("Goodbye");
 }
 

src/tty.rs

@@ -14,6 +14,13 @@ use libc::{self, winsize, c_int, c_char, pid_t, WNOHANG, WIFEXITED, WEXITSTATUS,
 /// Necessary to put this in static storage for `sigchld` to have access
 static mut PID: pid_t = 0;
 
+/// Exit flag
+///
+/// Calling exit() in the SIGCHLD handler sometimes causes opengl to deadlock,
+/// and the process hangs. Instead, this flag is set, and its status can be
+/// cheked via `process_should_exit`.
+static mut SHOULD_EXIT: bool = false;
+
 extern "C" fn sigchld(a: c_int) {
     let mut status: c_int = 0;
     unsafe {
@@ -29,9 +36,13 @@ extern "C" fn sigchld(a: c_int) {
         if !WIFEXITED(status) || WEXITSTATUS(status) != 0 {
             die!("child finished with error '{}'\n", status);
         }
-    }
 
-    ::std::process::exit(0);
+        SHOULD_EXIT = true;
+    }
+}
+
+pub fn process_should_exit() -> bool {
+    unsafe { SHOULD_EXIT }
 }
 
 pub enum Error {