ash: allow "trap NUM [SIG]..." syntax

While at it, make get_signum() return -1 for numeric strings >= NSIG.

function                                             old     new   delta
trapcmd                                              292     306     +14
get_signum                                           295     300      +5
builtin_trap                                         413     412      -1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 19/-1)              Total: 18 bytes

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

2 files changed, 8 insertions, 3 deletions

diff --git a/shell/ash.c b/shell/ash.c
index b4b0d5253..42e14cbc8 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -12981,13 +12981,18 @@ trapcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
                 return 0;
         }
 
+        /* Why the second check?
+         * "trap NUM [sig2]..." is the same as "trap - NUM [sig2]..."
+         * In this case, NUM is signal no, not an action.
+         */
         action = NULL;
-        if (ap[1])
+        if (ap[1] && !is_number(ap[0]))
                 action = *ap++;
+
         exitcode = 0;
         while (*ap) {
                 signo = get_signum(*ap);
-                if (signo < 0 || signo >= NSIG) {
+                if (signo < 0) {
                         /* Mimic bash message exactly */
                         ash_msg("%s: invalid signal specification", *ap);
                         exitcode = 1;
diff --git a/shell/hush.c b/shell/hush.c
index f9dad074f..11b33f40a 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -9745,7 +9745,7 @@ static int FAST_FUNC builtin_trap(char **argv)
                         sighandler_t handler;
 
                         sig = get_signum(*argv++);
-                        if (sig < 0 || sig >= NSIG) {
+                        if (sig < 0) {
                                 ret = EXIT_FAILURE;
                                 /* Mimic bash message exactly */
                                 bb_error_msg("trap: %s: invalid signal specification", argv[-1]);