sh: If exit is used without args from a trap action, exit on the signal.

This is useful so that it is easier to exit on a signal than to reset the
trap to default and resend the signal. It matches ksh93. POSIX says that
'exit' without args from a trap action uses the exit status from the last
command before the trap, which is different from 'exit $?' and matches this
if the previous command is assumed to have exited on the signal.

If the signal is SIGSTOP, SIGTSTP, SIGTTIN or SIGTTOU, or if the default
action for the signal is to ignore it, a normal _exit(2) is done with exit
status 128+signal_number.

1 files changed, 23 insertions, 4 deletions

diff --git a/bin/sh/trap.c b/bin/sh/trap.c
index d2e5308..048c75c 100644
--- a/bin/sh/trap.c
+++ b/bin/sh/trap.c
@@ -79,6 +79,7 @@ static volatile sig_atomic_t gotsig[NSIG];
 				/* indicates specified signal received */
 static int ignore_sigchld;	/* Used while handling SIGCHLD traps. */
 volatile sig_atomic_t gotwinch;
+static int last_trapsig;
 
 static int exiting;		/* exitshell() has been called */
 static int exiting_exitstatus;	/* value passed to exitshell() */
@@ -441,6 +442,7 @@ dotrap(void)
 					 */
 					if (i == SIGCHLD)
 						ignore_sigchld++;
+					last_trapsig = i;
 					savestatus = exitstatus;
 					evalstring(trap[i], 0);
 					exitstatus = savestatus;
@@ -495,9 +497,16 @@ exitshell_savedstatus(void)
 {
 	struct jmploc loc1, loc2;
 	char *p;
-
-	if (!exiting)
-		exiting_exitstatus = oexitstatus;
+	int sig = 0;
+	sigset_t sigs;
+
+	if (!exiting) {
+		if (in_dotrap && last_trapsig) {
+			sig = last_trapsig;
+			exiting_exitstatus = sig + 128;
+		} else
+			exiting_exitstatus = oexitstatus;
+	}
 	exitstatus = oexitstatus = exiting_exitstatus;
 	if (setjmp(loc1.loc)) {
 		goto l1;
@@ -515,5 +524,15 @@ l1:   handler = &loc2;			/* probably unnecessary */
 #if JOBS
 	setjobctl(0);
 #endif
-l2:   _exit(exiting_exitstatus);
+l2:
+	if (sig != 0 && sig != SIGSTOP && sig != SIGTSTP && sig != SIGTTIN &&
+	    sig != SIGTTOU) {
+		signal(sig, SIG_DFL);
+		sigemptyset(&sigs);
+		sigaddset(&sigs, sig);
+		sigprocmask(SIG_UNBLOCK, &sigs, NULL);
+		kill(getpid(), sig);
+		/* If the default action is to ignore, fall back to _exit(). */
+	}
+	_exit(exiting_exitstatus);
 }