From eba9be1b391c1fa87dd7557cf528ceaefd1f8d19 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Thu, 11 Feb 2021 15:25:22 -0700
Subject: [PATCH] cooperate with nohup

If SIGHUP is initially ignored, don't set a SIGHUP handler.
---
 racket/src/bc/src/salloc.c      | 8 ++++++++
 racket/src/rktio/rktio_signal.c | 8 +++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/racket/src/bc/src/salloc.c b/racket/src/bc/src/salloc.c
index 7d4f5150e4..549122071d 100644
--- a/racket/src/bc/src/salloc.c
+++ b/racket/src/bc/src/salloc.c
@@ -462,6 +462,14 @@ void scheme_set_signal_handler(int sig_id, Scheme_Signal_Handler_Proc proc) XFOR
 {
 #ifndef WINDOWS_PROCESSES
   struct sigaction sa;
+
+  if (sig_id == SIGHUP) {
+    /* cooperate with `nohup` by keeping SIHGUP as-is when ignored */
+    sigaction(SIGHUP, NULL, &sa);
+    if (sa.sa_handler == SIG_IGN)
+      return;
+  }
+
   sigemptyset(&sa.sa_mask);
   sa.sa_flags = 0;
   sa.sa_handler = (proc ? proc : SIG_IGN);
diff --git a/racket/src/rktio/rktio_signal.c b/racket/src/rktio/rktio_signal.c
index 73448ebd7a..d0e20eb0b7 100644
--- a/racket/src/rktio/rktio_signal.c
+++ b/racket/src/rktio/rktio_signal.c
@@ -68,7 +68,13 @@ void rktio_install_os_signal_handler(rktio_t *rktio)
 #if defined(RKTIO_SYSTEM_UNIX)
   rktio_set_signal_handler(SIGINT, user_break_hit);
   rktio_set_signal_handler(SIGTERM, term_hit);
-  rktio_set_signal_handler(SIGHUP, hup_hit);
+  {
+    struct sigaction sa;
+    sigemptyset(&sa.sa_mask);
+    sigaction(SIGHUP, NULL, &sa);
+    if (sa.sa_handler != SIG_IGN)
+      rktio_set_signal_handler(SIGHUP, hup_hit);
+  }
 #endif
 
 #if defined(RKTIO_SYSTEM_WINDOWS)