Re: Zsh does not follow POSIX when return is called during the action of a trap

[Peter Stephenson <p.stephenson@xxxxxxxxxxx>]

On Wed, 12 Mar 2014 13:49:18 -0400
Chet Ramey <chet.ramey@xxxxxxxx> wrote:
> On 3/12/14 1:03 PM, Peter Stephenson wrote:
> 
> > However, I'm trying to work out what happens with the case
> > 
> > |  trap '(exit BEFORE-RETURN); return EXPLICIT-RETURN-VALUE' SIGNAL
> > |
> > |  fn() {
> > |    (exit BEFORE-ACTION); -block here waiting for signal-
> > |  }
> > 
> > Should this exit with EXPLICIT-RETURN_VALUE or BEFORE-ACTION?  The
> > latter is easier to implement but my guess (without ploughing through
> > the standard) is EXPLICIT-RETURN-VALUE is right here.
> 
> The correct exit value is EXPLICIT-RETURN-VALUE.

OK, so I think the answer is as follows...  I'm out of time, I'll give
it a check with explicit return values tomorrow.

I'll also add some additional documentation for POSIX_TRAPS.

diff --git a/Src/builtin.c b/Src/builtin.c
index 9bcbcf7..0419c39 100644
--- a/Src/builtin.c
+++ b/Src/builtin.c
@@ -4688,9 +4688,10 @@ exit_pending;
 int
 bin_break(char *name, char **argv, UNUSED(Options ops), int func)
 {
-    int num = lastval, nump = 0;
+    int num = lastval, nump = 0, implicit;
 
     /* handle one optional numeric argument */
+    implicit = !*argv;
     if (*argv) {
 	num = mathevali(*argv++);
 	nump = 1;
@@ -4721,7 +4722,12 @@ bin_break(char *name, char **argv, UNUSED(Options ops), int func)
 	    retflag = 1;
 	    breaks = loops;
 	    lastval = num;
-	    if (trap_state == TRAP_STATE_PRIMED && trap_return == -2) {
+	    if (trap_state == TRAP_STATE_PRIMED && trap_return == -2 &&
+		/*
+		 * With POSIX, "return" on its own in a trap doesn't
+		 * update $? --- we keep the status from before the trap.
+		 */
+		!(isset(POSIXTRAPS) && implicit)) {
 		trap_state = TRAP_STATE_FORCE_RETURN;
 		trap_return = lastval;
 	    }
diff --git a/Src/signals.c b/Src/signals.c
index c8f5fbc..a6eb803 100644
--- a/Src/signals.c
+++ b/Src/signals.c
@@ -1155,6 +1155,7 @@ dotrapargs(int sig, int *sigtr, void *sigfn)
     char *name, num[4];
     int obreaks = breaks;
     int oretflag = retflag;
+    int olastval = lastval;
     int isfunc;
     int traperr, new_trap_state, new_trap_return;
 
@@ -1261,6 +1262,13 @@ dotrapargs(int sig, int *sigtr, void *sigfn)
     } else {
 	if (traperr && !EMULATION(EMULATE_SH))
 	    lastval = 1;
+	else {
+	    /*
+	     * With no explicit forced return, we keep the
+	     * lastval from before the trap ran.
+	     */
+	    lastval = olastval;
+	}
 	if (try_tryflag)
 	    errflag = traperr;
 	breaks += obreaks;

pws