From f00c7b5b4139ee54d675ea98630d09500a09b34d Mon Sep 17 00:00:00 2001
From: Michael Kerrisk <mtk.manpages@gmail.com>
Date: Fri, 19 Jun 2020 14:19:27 +0200
Subject: [PATCH] atoi.3: Add NOTES section explaining 0 return value on error

And note that this is not specified by POSIX.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
---
 man3/atoi.3 | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/man3/atoi.3 b/man3/atoi.3
index 3c6527a5b..87d1e1efd 100644
--- a/man3/atoi.3
+++ b/man3/atoi.3
@@ -126,6 +126,11 @@ only.
 .\" .BR atoll ()
 .\" function is present in glibc 2 since version 2.0.2, but
 .\" not in libc4 or libc5.
+.SH NOTES
+POSIX.1 leaves the return value of
+.BR atoi ()
+on error unspecified.
+On glibc, musl libc, and uClibc, 0 is returned on error.
 .SH SEE ALSO
 .BR atof (3),
 .BR strtod (3),