Add a few more functions which are safe to call from signal handlers,

and give a bit of advice.

Obtained from:	OpenBSD
MFC After:	1 week

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/libc/sys/sigaction.2 b/lib/libc/sys/sigaction.2
index 1d1c98f..51bd2b9 100644
--- a/lib/libc/sys/sigaction.2
+++ b/lib/libc/sys/sigaction.2
@@ -418,9 +418,29 @@ Realtime Interfaces:
 .Fn sigset ,
 .Fn timer_settime .
 .Pp
+ANSI C Interfaces:
+.Pp
+.Fn strcpy ,
+.Fn strcat ,
+.Fn strncpy ,
+.Fn strncat ,
+and perhaps some others.
+.Pp
+Extension Interfaces:
+.Pp
+.Fn strlcpy ,
+.Fn strlcat .
+.Pp
 All functions not in the above lists are considered to be unsafe
 with respect to signals.  That is to say, the behaviour of such
 functions when called from a signal handler is undefined.
+In general though, signal handlers should do little more than set a
+flag; most other actions are not safe.
+.Pp
+As well, inside the signal handler it is also considered more safe to
+make a copy the global variable
+.Va errno
+and restore it before returning from the signal handler.
 .Sh RETURN VALUES
 A 0 value indicated that the call succeeded.  A \-1 return value
 indicates an error occurred and