1	Wait + signals
2
3We had some bugs here which are hard to test in testsuite.
4
5Bug 1280 (http://busybox.net/bugs/view.php?id=1280):
6was misbehaving in interactive ash. Correct behavior:
7
8$ sleep 20 &
9$ wait
10^C
11$ wait
12^C
13$ wait
14^C
15...
16
17
18Bug 1984 (http://busybox.net/bugs/view.php?id=1984):
19traps were not triggering:
20
21trap_handler_usr () {
22    echo trap usr
23}
24trap_handler_int () {
25    echo trap int
26}
27trap trap_handler_usr USR1
28trap trap_handler_int INT
29sleep 3600 &
30echo "Please do: kill -USR1 $$"
31echo "or: kill -INT $$"
32while true; do wait; echo wait interrupted; done
33
34
35Bug 189 (https://bugs.busybox.net/show_bug.cgi?id=189)
36
37func() {
38    sleep 1
39}
40while (true); do
41    func
42    echo Looping
43done
44
45^C was observed to make ash processes geometrically multiply (!) instead
46of exiting. (true) in subshell does not seem to matter, as another user
47reports the same with:
48
49trap "echo USR1" USR1
50while true; do
51    echo Sleeping
52    sleep 5
53done
54
55Compat note.
56Bash version 3.2.0(1) exits this script at the receipt of SIGINT
57_only_ if it had two last children die from it.
58The following trace was obtained while periodically running
59"killall -SIGINT sleep; sleep 0.1; kill -SIGINT <bash_PID>":
60
6123:48:32.376707 clone(...) = 13528
6223:48:32.388706 waitpid(-1, 0xffc832ec, 0) = ? ERESTARTSYS (To be restarted)
6323:48:32.459761 --- SIGINT (Interrupt) @ 0 (0) ---
64    kill -SIGINT <bash_PID> is ignored, back to waiting:
6523:48:32.463706 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 13528
66    sleep exited with 0
6723:48:37.377557 --- SIGCHLD (Child exited) @ 0 (0) ---
6823:48:37.378451 clone(...) = 13538
6923:48:37.390708 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 13538
70    sleep was killed by "killall -SIGINT sleep"
7123:48:38.523944 --- SIGCHLD (Child exited) @ 0 (0) ---
7223:48:38.524861 clone(...) = 13542
7323:48:38.538706 waitpid(-1, 0xffc832ec, 0) = ? ERESTARTSYS (To be restarted)
7423:48:38.624761 --- SIGINT (Interrupt) @ 0 (0) ---
75    kill -SIGINT <bash_PID> is ignored, back to waiting:
7623:48:38.628706 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 13542
77    sleep exited with 0
7823:48:43.525674 --- SIGCHLD (Child exited) @ 0 (0) ---
7923:48:43.526563 clone(...) = 13545
8023:48:43.538709 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 13545
81    sleep was killed by "killall -SIGINT sleep"
8223:48:44.466848 --- SIGCHLD (Child exited) @ 0 (0) ---
8323:48:44.467735 clone(...) = 13549
8423:48:44.481706 waitpid(-1, 0xffc832ec, 0) = ? ERESTARTSYS (To be restarted)
8523:48:44.567757 --- SIGINT (Interrupt) @ 0 (0) ---
86    kill -SIGINT <bash_PID> is ignored, back to waiting:
8723:48:44.571706 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 13549
88    sleep exited with 0
8923:48:49.468553 --- SIGCHLD (Child exited) @ 0 (0) ---
9023:48:49.469445 clone(...) = 13551
9123:48:49.481708 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 13551
92    sleep was killed by "killall -SIGINT sleep"
9323:48:50.515837 --- SIGCHLD (Child exited) @ 0 (0) ---
9423:48:50.516718 clone(...) = 13555
9523:48:50.530706 waitpid(-1, 0xffc832ec, 0) = ? ERESTARTSYS (To be restarted)
9623:48:50.615761 --- SIGINT (Interrupt) @ 0 (0) ---
97    kill -SIGINT <bash_PID> is ignored, back to waiting:
9823:48:50.619705 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 13555
99    sleep was killed by "killall -SIGINT sleep".
100    This is the second one in a row. Kill ourself:
10123:48:51.504604 kill(13515, SIGINT)     = 0
10223:48:51.504689 --- SIGINT (Interrupt) @ 0 (0) ---
10323:48:51.504915 +++ killed by SIGINT +++
104
105As long as there is at least one "sleep 5" which exited successfully
106(not killed by SIGINT), bash continues. This is not documented anywhere
107AFAIKS.
108
109Why keyboard ^C acts differently?
110
11100:08:07.655985 clone(...) = 14270
11200:08:07.669707 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0) = 14270
11300:08:12.656872 --- SIGCHLD (Child exited) @ 0 (0) ---
11400:08:12.657743 clone(...) = 14273
11500:08:12.671708 waitpid(-1, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGINT}], 0) = 14273
11600:08:13.810778 --- SIGINT (Interrupt) @ 0 (0) ---
11700:08:13.818705 kill(14269, SIGINT)     = 0
11800:08:13.820103 --- SIGINT (Interrupt) @ 0 (0) ---
11900:08:13.820925 +++ killed by SIGINT +++
120
121Perhaps because at the moment bash got SIGINT it had no children?
122(it did not manage to spawn new sleep yet, see the trace)
123