signal-safety.7: Note async-signal-safety details for errno

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/signal-safety.7 b/man7/signal-safety.7
index a70251f1b0e12f37bd1b742d0e70efe7a4bb1749..f70eb814fd91509186dd2a0cd2ed38aad2d59278 100644 (file)
--- a/man7/signal-safety.7
+++ b/man7/signal-safety.7
@@ -285,7 +285,7 @@ Function    Notes
 \fBwmemset\fP(3)       Added in POSIX.1-2008 TC2
 \fBwrite\fP(2)
 .TE
-.sp 1
+.PP
 Notes:
 .IP * 3
 POSIX.1-2001 and POSIX.1-2001 TC2 required the functions
@@ -320,6 +320,14 @@ Asynchronous signal handlers that call functions which are cancellation
 points and nest over regions of deferred cancellation may trigger
 cancellation whose behavior is as if asynchronous cancellation had
 occurred and may cause application state to become inconsistent.
+.\"
+.SS errno
+Fetching and setting the value of
+.I errno
+is async-signal-safe provided that the signal handler saves
+.I errno
+on entry and restores its value before returning.
+.\"
 .SS Deviations in the GNU C library
 The following known deviations from the standard occur in
 the GNU C library: