From b9ad845d017f3a07c44c40a7b5cfd937d637bc19 Mon Sep 17 00:00:00 2001
From: Michael Kerrisk <mtk.manpages@gmail.com>
Date: Sun, 16 Apr 2017 20:56:20 +0200
Subject: [PATCH] sigprocmask.2: 'set' and 'oldset' can both be NULL

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
---
 man2/sigprocmask.2 | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/man2/sigprocmask.2 b/man2/sigprocmask.2
index 499fd0cc6..ff4d1e19b 100644
--- a/man2/sigprocmask.2
+++ b/man2/sigprocmask.2
@@ -158,6 +158,12 @@ or
 See
 .BR sigsetops (3)
 for details on manipulating signal sets.
+
+Note that it is permissible (although not very useful) to specify both
+.I set
+and
+.I oldset
+as NULL.
 .\"
 .SS C library/kernel differences