From e4d7b884cde18ec19375cdd0de159822e4d43493 Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Sun, 27 Aug 2023 08:47:33 +1000
Subject: [PATCH] Cleanup SIGHUP handling and forking server to background

Ensure we ignore SIGHUP once the TerminalUI is gone as it will be
sent again on fork, fix the parent process terminating due to trying
to write to stdout after it was closed.

Fixes #4960
---
 src/terminal_ui.cc | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/src/terminal_ui.cc b/src/terminal_ui.cc
index f87a914e..c769816b 100644
--- a/src/terminal_ui.cc
+++ b/src/terminal_ui.cc
@@ -429,7 +429,7 @@ static constexpr StringView assistant_dilbert[] =
 template<typename T> T sq(T x) { return x * x; }
 
 static sig_atomic_t resize_pending = 0;
-static sig_atomic_t stdin_closed = 0;
+static sig_atomic_t terrminal_hangedup = 0;
 
 template<sig_atomic_t* signal_flag>
 static void signal_handler(int)
@@ -465,7 +465,7 @@ TerminalUI::TerminalUI()
     enable_mouse(true);
 
     set_signal_handler(SIGWINCH, &signal_handler<&resize_pending>);
-    set_signal_handler(SIGHUP, &signal_handler<&stdin_closed>);
+    set_signal_handler(SIGHUP, &signal_handler<&terrminal_hangedup>);
     set_signal_handler(SIGTSTP, [](int){ TerminalUI::instance().suspend(); });
 
     check_resize(true);
@@ -474,11 +474,13 @@ TerminalUI::TerminalUI()
 
 TerminalUI::~TerminalUI()
 {
-    enable_mouse(false);
-    restore_terminal();
-    tcsetattr(STDIN_FILENO, TCSAFLUSH, &m_original_termios);
+    if (not terrminal_hangedup) {
+        enable_mouse(false);
+        restore_terminal();
+        tcsetattr(STDIN_FILENO, TCSAFLUSH, &m_original_termios);
+    }
     set_signal_handler(SIGWINCH, SIG_DFL);
-    set_signal_handler(SIGHUP, SIG_DFL);
+    set_signal_handler(SIGHUP, SIG_IGN);
     set_signal_handler(SIGTSTP, SIG_DFL);
 }
 
@@ -666,10 +668,10 @@ void TerminalUI::check_resize(bool force)
 
 Optional<Key> TerminalUI::get_next_key()
 {
-    if (stdin_closed)
+    if (terrminal_hangedup)
     {
         set_signal_handler(SIGWINCH, SIG_DFL);
-        set_signal_handler(SIGHUP, SIG_DFL);
+        set_signal_handler(SIGHUP, SIG_IGN);
         if (m_window)
             m_window.destroy();
         m_stdin_watcher.disable();
@@ -691,7 +693,7 @@ Optional<Key> TerminalUI::get_next_key()
         if (unsigned char c = 0; read(STDIN_FILENO, &c, 1) == 1)
             return c;
 
-        stdin_closed = 1;
+        terrminal_hangedup = 1;
         return {};
     };