Add support for set -o pipefail

With the pipefail option set, the exit status of a pipeline is 0 if all
commands succeed, or the return status of the rightmost command that
fails.  This can help stronger error checking, but is not a silver
bullet.  For example, commands will exhibit a non-zero exit status if
they're killed by a SIGPIPE when writing to a pipe.  Yet pipefail was
considered useful enough to be included in the next POSIX standard.

This implementation remembers the value of the pipefail option when
a pipeline is started, as described as option 1) in

  https://www.austingroupbugs.net/view.php?id=789#c4102

Requested by ajacoutot@, ok millert@

bin/ksh/jobs.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: jobs.c,v 1.61 2019/06/28 13:34:59 deraadt Exp $	*/
+/*	$OpenBSD: jobs.c,v 1.62 2020/07/07 10:33:58 jca Exp $	*/
 
 /*
  * Process and job control
@@ -70,6 +70,7 @@ struct proc {
 #define JF_REMOVE	0x200	/* flagged for removal (j_jobs()/j_notify()) */
 #define JF_USETTYMODE	0x400	/* tty mode saved if process exits normally */
 #define JF_SAVEDTTYPGRP	0x800	/* j->saved_ttypgrp is valid */
+#define JF_PIPEFAIL	0x1000	/* pipefail on when job was started */
 
 typedef struct job Job;
 struct job {
@@ -421,6 +422,8 @@ exchild(struct op *t, int flags, volatile int *xerrok,
 		 */
 		j->flags = (flags & XXCOM) ? JF_XXCOM :
 		    ((flags & XBGND) ? 0 : (JF_FG|JF_USETTYMODE));
+		if (Flag(FPIPEFAIL))
+			j->flags |= JF_PIPEFAIL;
 		timerclear(&j->usrtime);
 		timerclear(&j->systime);
 		j->state = PRUNNING;
@@ -1084,7 +1087,30 @@ j_waitj(Job *j,
 
 	j_usrtime = j->usrtime;
 	j_systime = j->systime;
-	rv = j->status;
+
+	if (j->flags & JF_PIPEFAIL) {
+		Proc *p;
+		int status;
+
+		rv = 0;
+		for (p = j->proc_list; p != NULL; p = p->next) {
+			switch (p->state) {
+			case PEXITED:
+				status = WEXITSTATUS(p->status);
+				break;
+			case PSIGNALLED:
+				status = 128 + WTERMSIG(p->status);
+				break;
+			default:
+				status = 0;
+				break;
+			}
+			if (status)
+				rv = status;
+		}
+	} else
+		rv = j->status;
+
 
 	if (!(flags & JW_ASYNCNOTIFY) &&
 	    (!Flag(FMONITOR) || j->state != PSTOPPED)) {

bin/ksh/ksh.1

@@ -1,8 +1,8 @@
-.\"	$OpenBSD: ksh.1,v 1.208 2019/11/26 22:49:01 jmc Exp $
+.\"	$OpenBSD: ksh.1,v 1.209 2020/07/07 10:33:58 jca Exp $
 .\"
 .\"	Public Domain
 .\"
-.Dd $Mdocdate: November 26 2019 $
+.Dd $Mdocdate: July 7 2020 $
 .Dt KSH 1
 .Os
 .Sh NAME
@@ -361,7 +361,9 @@ token to form pipelines, in which the standard output of each command but the
 last is piped (see
 .Xr pipe 2 )
 to the standard input of the following command.
-The exit status of a pipeline is that of its last command.
+The exit status of a pipeline is that of its last command, unless the
+.Ic pipefail
+option is set.
 A pipeline may be prefixed by the
 .Ql \&!
 reserved word, which causes the exit status of the pipeline to be logically
@@ -3664,6 +3666,10 @@ See the
 and
 .Ic pwd
 commands above for more details.
+.It Ic pipefail
+The exit status of a pipeline is the exit status of the rightmost
+command in the pipeline that doesn't return 0, or 0 if all commands
+returned a 0 exit status.
 .It Ic posix
 Enable POSIX mode.
 See

bin/ksh/misc.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: misc.c,v 1.73 2019/06/28 13:34:59 deraadt Exp $	*/
+/*	$OpenBSD: misc.c,v 1.74 2020/07/07 10:33:58 jca Exp $	*/
 
 /*
  * Miscellaneous functions
@@ -147,6 +147,7 @@ const struct option sh_options[] = {
 	{ "notify",	'b',		OF_ANY },
 	{ "nounset",	'u',		OF_ANY },
 	{ "physical",	  0,		OF_ANY }, /* non-standard */
+	{ "pipefail",	  0,		OF_ANY }, /* non-standard */
 	{ "posix",	  0,		OF_ANY }, /* non-standard */
 	{ "privileged",	'p',		OF_ANY },
 	{ "restricted",	'r',	    OF_CMDLINE },

bin/ksh/sh.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: sh.h,v 1.75 2019/02/20 23:59:17 schwarze Exp $	*/
+/*	$OpenBSD: sh.h,v 1.76 2020/07/07 10:33:58 jca Exp $	*/
 
 /*
  * Public Domain Bourne/Korn shell
@@ -158,6 +158,7 @@ enum sh_flag {
 	FNOTIFY,	/* -b: asynchronous job completion notification */
 	FNOUNSET,	/* -u: using an unset var is an error */
 	FPHYSICAL,	/* -o physical: don't do logical cd's/pwd's */
+	FPIPEFAIL,	/* -o pipefail: all commands in pipeline can affect $? */
 	FPOSIX,		/* -o posix: be posixly correct */
 	FPRIVILEGED,	/* -p: use suid_profile */
 	FRESTRICTED,	/* -r: restricted shell */

regress/bin/ksh/obsd-regress.t

@@ -1,4 +1,4 @@
-#	$OpenBSD: obsd-regress.t,v 1.11 2020/05/22 08:45:23 anton Exp $
+#	$OpenBSD: obsd-regress.t,v 1.12 2020/07/07 10:33:58 jca Exp $
 
 #
 # ksh regression tests from OpenBSD
@@ -514,3 +514,91 @@ description:
 stdin:
 	kill -s SIGINFO $$
 ---
+
+name: pipeline-pipefail-1
+description:
+	check pipeline return status
+stdin:
+	set -o pipefail
+	true | true
+---
+
+name: pipeline-pipefail-2
+description:
+	check pipeline return status
+stdin:
+	set -o pipefail
+	false | true
+expected-exit: e == 1
+---
+
+name: pipeline-pipefail-3
+description:
+	check pipeline return status
+stdin:
+	set -o pipefail
+	true | false
+expected-exit: e == 1
+---
+
+name: pipeline-pipefail-4
+description:
+	check pipeline return status
+stdin:
+	set -o pipefail
+	! false | true
+---
+
+name: pipeline-pipefail-errexit-1
+description:
+	check pipeline return status
+stdin:
+	set -e
+	false | true
+	echo "ok"
+expected-stdout: ok
+---
+
+name: pipeline-pipefail-errexit-2
+description:
+	check pipeline return status
+stdin:
+	set -e
+	set -o pipefail
+	false | true
+	echo "should not print"
+expected-exit: e == 1
+expected-stdout:
+---
+
+name: pipeline-pipefail-errexit-3
+description:
+	check pipeline return status
+stdin:
+	set -e
+	set -o pipefail
+	false | true || echo "ok"
+expected-stdout: ok
+---
+
+name: pipeline-pipefail-check-time-1
+description:
+	check pipeline return status
+stdin:
+	false | true &
+	p=$!
+	set -o pipefail
+	wait $p
+---
+
+name: pipeline-pipefail-check-time-2
+description:
+	check pipeline return status
+stdin:
+	set -o pipefail
+	false | true &
+	p=$!
+	set +o pipefail
+	wait $p
+expected-exit: e == 1
+---