From 1cef87d79009782e786b85ce6b0adf3bb39b9833 Mon Sep 17 00:00:00 2001
From: ridiculousfish <rf@fishshell.com>
Date: Sat, 5 Sep 2020 12:38:21 -0700
Subject: [PATCH] Use anon semaphores only on Linux

On BSDs, anonymous semaphores are implemented using a file descriptor
which is not marked CLOEXEC, so it gets leaked into child processes.
Use ordinary pipes instead of semaphores everywhere except Linux.

Fixes #7304
---
 src/topic_monitor.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/topic_monitor.cpp b/src/topic_monitor.cpp
index 5bc8dacb3..1384fafed 100644
--- a/src/topic_monitor.cpp
+++ b/src/topic_monitor.cpp
@@ -39,7 +39,9 @@ wcstring generation_list_t::describe() const {
 
 binary_semaphore_t::binary_semaphore_t() : sem_ok_(false) {
     // sem_init always fails with ENOSYS on Mac and has an annoying deprecation warning.
-#ifndef __APPLE__
+    // On BSD sem_init uses a file descriptor under the hood which doesn't get CLOEXEC (see #7304).
+    // So use fast semaphores on Linux only.
+#ifdef __linux__
     sem_ok_ = (0 == sem_init(&sem_, 0, 0));
 #endif
     if (!sem_ok_) {