jobs: Fix waitcmd busy loop

We need to clear gotsigchld in waitproc because it is used as
a loop conditional for the waitcmd case.  Without it waitcmd
may busy loop after a SIGCHLD.

This patch also changes gotsigchld into a volatile sig_atomic_t
to prevent compilers from optimising its accesses away.

Fixes: 6c691b3e5099 ("jobs: Only clear gotsigchld when waiting...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

src/jobs.c

diff --git a/src/jobs.c b/src/jobs.c
index 0926360..d4c13c0 100644
--- a/src/jobs.c
+++ b/src/jobs.c
@@ -1136,7 +1136,6 @@
 	rpid = 1;
 
 	do {
-		gotsigchld = 0;
 		pid = waitone(block, jp);
 		rpid &= !!pid;
 
@@ -1176,6 +1175,7 @@
 #endif
 
 	do {
+		gotsigchld = 0;
 		do
 			err = wait3(status, flags, NULL);
 		while (err < 0 && errno == EINTR);

src/trap.c

diff --git a/src/trap.c b/src/trap.c
index 82e7ece..cd84814 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -76,7 +76,7 @@
 /* last pending signal */
 volatile sig_atomic_t pending_sig;
 /* received SIGCHLD */
-int gotsigchld;
+volatile sig_atomic_t gotsigchld;
 
 extern char *signal_names[];
 

src/trap.h

diff --git a/src/trap.h b/src/trap.h
index 4c455a8..beaf660 100644
--- a/src/trap.h
+++ b/src/trap.h
@@ -39,7 +39,7 @@
 extern int trapcnt;
 extern char sigmode[];
 extern volatile sig_atomic_t pending_sig;
-extern int gotsigchld;
+extern volatile sig_atomic_t gotsigchld;
 
 int trapcmd(int, char **);
 void setsignal(int);