ash: fix ash-signals/signal8 testcase failure

function                                             old     new   delta
killcmd                                              109     224    +115
kill_main                                            882     910     +28
changepath                                           194     195      +1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 144/0)             Total: 144 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

procps/kill.c

@@ -206,9 +206,27 @@ int kill_main(int argc, char **argv)
 
 	/* Looks like they want to do a kill. Do that */
 	while (arg) {
-		/* Support shell 'space' trick */
-		if (arg[0] == ' ')
-			arg++;
+#if ENABLE_ASH || ENABLE_HUSH
+		/*
+		 * We need to support shell's "hack formats" of
+		 * " -PRGP_ID" (yes, with a leading space)
+		 * and " PID1 PID2 PID3" (with degenerate case "")
+		 */
+		while (*arg != '\0') {
+			char *end;
+			if (*arg == ' ')
+				arg++;
+			pid = bb_strtoi(arg, &end, 10);
+			if (errno && (errno != EINVAL || *end != ' ')) {
+				bb_error_msg("invalid number '%s'", arg);
+				errors++;
+			} else if (kill(pid, signo) != 0) {
+				bb_perror_msg("can't kill pid %d", (int)pid);
+				errors++;
+			}
+			arg = end; /* can only point to ' ' or '\0' now */
+		}
+#else
 		pid = bb_strtoi(arg, NULL, 10);
 		if (errno) {
 			bb_error_msg("invalid number '%s'", arg);
@@ -217,6 +235,7 @@ int kill_main(int argc, char **argv)
 			bb_perror_msg("can't kill pid %d", (int)pid);
 			errors++;
 		}
+#endif
 		arg = *++argv;
 	}
 	return errors;

shell/ash.c

@@ -3783,18 +3783,51 @@ setjobctl(int on)
 static int FAST_FUNC
 killcmd(int argc, char **argv)
 {
-	int i = 1;
 	if (argv[1] && strcmp(argv[1], "-l") != 0) {
+		int i = 1;
 		do {
 			if (argv[i][0] == '%') {
-				struct job *jp = getjob(argv[i], 0);
-				unsigned pid = jp->ps[0].ps_pid;
-				/* Enough space for ' -NNN<nul>' */
-				argv[i] = alloca(sizeof(int)*3 + 3);
-				/* kill_main has matching code to expect
-				 * leading space. Needed to not confuse
-				 * negative pids with "kill -SIGNAL_NO" syntax */
-				sprintf(argv[i], " -%u", pid);
+				/*
+				 * "kill %N" - job kill
+				 * Converting to pgrp / pid kill
+				 */
+				struct job *jp;
+				char *dst;
+				int j, n;
+
+				jp = getjob(argv[i], 0);
+				/*
+				 * In jobs started under job control, we signal
+				 * entire process group by kill -PGRP_ID.
+				 * This happens, f.e., in interactive shell.
+				 *
+				 * Otherwise, we signal each child via
+				 * kill PID1 PID2 PID3.
+				 * Testcases:
+				 * sh -c 'sleep 1|sleep 1 & kill %1'
+				 * sh -c 'true|sleep 2 & sleep 1; kill %1'
+				 * sh -c 'true|sleep 1 & sleep 2; kill %1'
+				 */
+				n = jp->nprocs; /* can't be 0 (I hope) */
+				if (jp->jobctl)
+					n = 1;
+				dst = alloca(n * sizeof(int)*4);
+				argv[i] = dst;
+				for (j = 0; j < n; j++) {
+					struct procstat *ps = &jp->ps[j];
+					/* Skip non-running and not-stopped members
+					 * (i.e. dead members) of the job
+					 */
+					if (ps->ps_status != -1 && !WIFSTOPPED(ps->ps_status))
+						continue;
+					/*
+					 * kill_main has matching code to expect
+					 * leading space. Needed to not confuse
+					 * negative pids with "kill -SIGNAL_NO" syntax
+					 */
+					dst += sprintf(dst, jp->jobctl ? " -%u" : " %u", (int)ps->ps_pid);
+				}
+				*dst = '\0';
 			}
 		} while (argv[++i]);
 	}
@@ -4227,8 +4260,9 @@ waitcmd(int argc UNUSED_PARAM, char **argv)
 					break;
 				job = job->prev_job;
 			}
-		} else
+		} else {
 			job = getjob(*argv, 0);
+		}
 		/* loop until process terminated or stopped */
 		while (job->state == JOBRUNNING)
 			blocking_wait_with_raise_on_sig();
@@ -4724,7 +4758,7 @@ forkchild(struct job *jp, union node *n, int mode)
 #if JOBS
 	/* do job control only in root shell */
 	doing_jobctl = 0;
-	if (mode != FORK_NOJOB && jp->jobctl && !oldlvl) {
+	if (mode != FORK_NOJOB && jp->jobctl && oldlvl == 0) {
 		pid_t pgrp;
 
 		if (jp->nprocs == 0)
@@ -4750,7 +4784,7 @@ forkchild(struct job *jp, union node *n, int mode)
 				ash_msg_and_raise_error("can't open '%s'", bb_dev_null);
 		}
 	}
-	if (!oldlvl) {
+	if (oldlvl == 0) {
 		if (iflag) { /* why if iflag only? */
 			setsignal(SIGINT);
 			setsignal(SIGTERM);

shell/ash_test/ash-signals/sigint1.right

@@ -0,0 +1 @@
+Sending SIGINT to main shell PID

shell/ash_test/ash-signals/sigint1.tests

@@ -0,0 +1,41 @@
+# What should happen if non-interactive shell gets SIGINT?
+
+(sleep 1; echo Sending SIGINT to main shell PID; exec kill -INT $$) &
+
+# We create a child which exits with 0 even on SIGINT
+# (This is truly necessary only if SIGINT is generated by ^C,
+# in this testcase even bare "sleep 2" would do because
+# we don't send SIGINT _to_ the_ child_...)
+$THIS_SH -c 'trap "exit 0" SIGINT; sleep 2'
+
+# In one second, we (main shell) get SIGINT here.
+# The question is whether we should, or should not, exit.
+
+# bash will not stop here. It will execute next command(s).
+
+# The rationale for this is described here:
+# http://www.cons.org/cracauer/sigint.html
+#
+# Basically, bash will not exit on SIGINT immediately if it waits
+# for a child. It will wait for the child to exit.
+# If child exits NOT by dying on SIGINT, then bash will not exit.
+#
+# The idea is that the following script:
+# | emacs file.txt
+# | more cmds
+# User may use ^C to interrupt editor's ops like search. But then
+# emacs exits normally. User expects that script doesn't stop.
+#
+# This is a nice idea, but detecting "did process really exit
+# with SIGINT?" is racy. Consider:
+# | bash -c 'while true; do /bin/true; done'
+# When ^C is pressed while bash waits for /bin/true to exit,
+# it may happen that /bin/true exits with exitcode 0 before
+# ^C is delivered to it as SIGINT. bash will see SIGINT, then
+# it will see that child exited with 0, and bash will NOT EXIT.
+
+# Therefore we do not implement bash behavior.
+# I'd say that emacs need to put itself into a separate pgrp
+# to isolate shell from getting stray SIGINTs from ^C.
+
+echo Next command after SIGINT was executed

shell/hush_test/hush-misc/sigint1.right

@@ -0,0 +1 @@
+Sending SIGINT to main shell PID

shell/hush_test/hush-misc/sigint1.tests

@@ -0,0 +1,41 @@
+# What should happen if non-interactive shell gets SIGINT?
+
+(sleep 1; echo Sending SIGINT to main shell PID; exec kill -INT $$) &
+
+# We create a child which exits with 0 even on SIGINT
+# (This is truly necessary only if SIGINT is generated by ^C,
+# in this testcase even bare "sleep 2" would do because
+# we don't send SIGINT _to_ the_ child_...)
+$THIS_SH -c 'trap "exit 0" SIGINT; sleep 2'
+
+# In one second, we (main shell) get SIGINT here.
+# The question is whether we should, or should not, exit.
+
+# bash will not stop here. It will execute next command(s).
+
+# The rationale for this is described here:
+# http://www.cons.org/cracauer/sigint.html
+#
+# Basically, bash will not exit on SIGINT immediately if it waits
+# for a child. It will wait for the child to exit.
+# If child exits NOT by dying on SIGINT, then bash will not exit.
+#
+# The idea is that the following script:
+# | emacs file.txt
+# | more cmds
+# User may use ^C to interrupt editor's ops like search. But then
+# emacs exits normally. User expects that script doesn't stop.
+#
+# This is a nice idea, but detecting "did process really exit
+# with SIGINT?" is racy. Consider:
+# | bash -c 'while true; do /bin/true; done'
+# When ^C is pressed while bash waits for /bin/true to exit,
+# it may happen that /bin/true exits with exitcode 0 before
+# ^C is delivered to it as SIGINT. bash will see SIGINT, then
+# it will see that child exited with 0, and bash will NOT EXIT.
+
+# Therefore we do not implement bash behavior.
+# I'd say that emacs need to put itself into a separate pgrp
+# to isolate shell from getting stray SIGINTs from ^C.
+
+echo Next command after SIGINT was executed