Module Name: src
Committed By: martin
Date: Sat Aug 12 12:53:18 UTC 2023
Modified Files:
src/share/man/man7 [netbsd-10]: signal.7
Log Message:
Pull up following revision(s) (requested by riastradh in ticket #325):
share/man/man7/signal.7: revision 1.27
share/man/man7/signal.7: revision 1.28
signal(7): Clarify quirky SysV-inspired SIGCHLD semantics.
Suggest a portable alternative approach for detaching subprocesses.
Break wall of text into paragraphs while here.
signal(7): Clarify semantics of SIGCHLD with SIG_IGN or SA_NOCLDWAIT.
The semantics is not just a nonportable hack for SysV compatibility;
it is enshrined in POSIX.
Related: PR 57527
To generate a diff of this commit:
cvs rdiff -u -r1.26 -r1.26.4.1 src/share/man/man7/signal.7
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/share/man/man7/signal.7
diff -u src/share/man/man7/signal.7:1.26 src/share/man/man7/signal.7:1.26.4.1
--- src/share/man/man7/signal.7:1.26 Sun May 30 07:17:01 2021
+++ src/share/man/man7/signal.7 Sat Aug 12 12:53:17 2023
@@ -1,4 +1,4 @@
-.\" $NetBSD: signal.7,v 1.26 2021/05/30 07:17:01 dholland Exp $
+.\" $NetBSD: signal.7,v 1.26.4.1 2023/08/12 12:53:17 martin Exp $
.\"
.\" Copyright (c) 1999, 2016 The NetBSD Foundation, Inc.
.\" All rights reserved.
@@ -401,18 +401,25 @@ immediate children exits and can be wait
.Xr wait 2
family of functions.
The default action is to do nothing.
-As a special case hack, if
+.Pp
+As a special case, if a child exits when its parent process has
.Dv SIGCHLD
-is ignored (not merely blocked) when a process is
-.Em created ,
-it is detached from its parent immediately so it need not be waited
-for.
-This behavior is a System V historic wart, implemented in
-.Nx
-only for compatibility.
-It is not portable, not recommended, and should not be used by new
-code.
-.\" XXX should refer to something that can be used by new code...
+ignored
+.Pq not merely blocked
+by having its signal handler set to
+.Dv SIG_IGN ,
+or if the signal action has the
+.Dv SA_NOCLDWAIT
+flag set
+.Pq Xr sigaction 2 ,
+then the child is detached so that
+.Xr wait 2
+in the parent will wait for
+.Em all
+children to exit and then fail with
+.Er ECHILD
+without returning any information about any specific child processes.
+.Pp
The number for
.Dv SIGCHLD
is\~20.
