From 94ac3084e156b87869f8b336ae0a3fd752743179 Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Mon, 2 Nov 2020 22:52:59 +1100
Subject: [PATCH] Handle reading from stdin returning 0

0 means stdin was closed, this is quite unexpected as we would usually
get a SIGHUP, but it looks like in some rare case this happens and
it leads to an infinite loop trying to handle stdin events (as it
will always be readable from now on).

Fixes #3557
---
 src/ncurses_ui.cc | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/ncurses_ui.cc b/src/ncurses_ui.cc
index 732f009f..e52748c9 100644
--- a/src/ncurses_ui.cc
+++ b/src/ncurses_ui.cc
@@ -316,7 +316,7 @@ bool NCursesUI::Palette::set_change_colors(bool change_colors)
 }
 
 static sig_atomic_t resize_pending = 0;
-static sig_atomic_t sighup_raised = 0;
+static sig_atomic_t stdin_closed = 0;
 
 template<sig_atomic_t* signal_flag>
 static void signal_handler(int)
@@ -351,7 +351,7 @@ NCursesUI::NCursesUI()
     enable_mouse(true);
 
     set_signal_handler(SIGWINCH, &signal_handler<&resize_pending>);
-    set_signal_handler(SIGHUP, &signal_handler<&sighup_raised>);
+    set_signal_handler(SIGHUP, &signal_handler<&stdin_closed>);
     set_signal_handler(SIGTSTP, [](int){ NCursesUI::instance().suspend(); });
 
     check_resize(true);
@@ -577,7 +577,7 @@ void NCursesUI::check_resize(bool force)
 
 Optional<Key> NCursesUI::get_next_key()
 {
-    if (sighup_raised)
+    if (stdin_closed)
     {
         set_signal_handler(SIGWINCH, SIG_DFL);
         set_signal_handler(SIGHUP, SIG_DFL);
@@ -596,9 +596,13 @@ Optional<Key> NCursesUI::get_next_key()
     }
 
     static auto get_char = []() -> Optional<unsigned char> {
-        unsigned char c = 0;
-        if (fd_readable(STDIN_FILENO) and read(STDIN_FILENO, &c, 1) == 1)
+        if (not fd_readable(STDIN_FILENO))
+            return {};
+
+        if (unsigned char c = 0; read(STDIN_FILENO, &c, 1) == 1)
             return c;
+
+        stdin_closed = 1;
         return {};
     };