From: "Eduardo A. Bustamante López" <dualbus@gmail.com>
To: zsh-workers@zsh.org
Subject: Zsh does not follow POSIX when return is called during the action of a trap
Date: Wed, 12 Mar 2014 08:36:27 -0700 [thread overview]
Message-ID: <20140312153627.GA15209@dualbus.me> (raw)
Hi! I first reported this bug to bug-bash, but since it also applies
to zsh, I wanted you to know about it. I'll use the same report I
sent, since it's the same problem:
According to POSIX:
| The value of the special parameter '?' shall be set to n, an
| unsigned decimal integer, or to the exit status of the last command
| executed if n is not specified. If the value of n is greater than
| 255, the results are undefined. When return is executed in a trap
| action, the last command is considered to be the command that
| executed immediately preceding the trap action.
Source (EXIT STATUS section):
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#return
So, what I understand from this:
(1) When return is called without a numeric argument, the code
returned is that of the `last command'.
(2) The `last command' is defined as: ``[...] the command that
executed immediately preceding the trap action''.
Taking the SYNOPSIS for the trap builtin:
| trap n [condition...]
| trap [action condition...]
and from DESCRIPTION:
| Each time trap is invoked, the action argument shall be processed in
| a manner equivalent to:
|
| eval action
Source:
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#trap
So as I read it, `action' refers to the whole string.
Now, this means, taking the following pseudo-code:
| trap '(exit BEFORE-RETURN); return' SIGNAL
|
| fn() {
| (exit BEFORE-ACTION); -block here waiting for signal-
| }
If that script receives SIGNAL, it should return the BEFORE-ACTION
exit code, and not the BEFORE-RETURN exit code.
Testing this is a bit tricky, because there's no simple way of
blocking to wait for a signal in a way that it doesn't affect our
testing, so the bes I could come up with is this:
### begin test script
code='trap "(exit 2); return" USR1
f() {
{ echo; kill -USR1 $$; } | exit 3
return 5
}
(exit 7); f
'
shells=(
bash
'bash --posix'
ksh
mksh
dash
'busybox sh'
zsh
jsh
)
for attempt in {1..1000}; do
for shell in "address@hidden"; do
printf '%s: %s\n' "$shell" "$($shell -c "$code"; echo $?)"
done
done | sort | uniq -c
### end test script
And sample output from this script:
969 bash: 2
31 bash: 5
979 bash --posix: 2
21 bash --posix: 5
1000 busybox sh: 5
971 dash: 3
29 dash: 5
118 jsh: 3
882 jsh: 5
1 ksh: 0
999 ksh: 3
970 mksh: 3
30 mksh: 5
6 zsh: 2
994 zsh: 3
Most of the time, zsh returns the correct code (3, BEFORE-ACTION),
but sometimes it returns 2, which is BEFORE-RETURN (and it should not).
The versions tested are:
bash --version|head -n1:
GNU bash, version 4.3.0(2)-release (x86_64-unknown-linux-gnu)
zsh --version|head -n1:
zsh 4.3.17 (x86_64-unknown-linux-gnu)
ksh --version|head -n1:
version sh (AT&T Research) 93u+ 2012-02-29
mksh -c 'echo "$KSH_VERSION"':
@(#)MIRBSD KSH R40 2012/07/20 Debian-7
apt-cache policy dash|grep Installed:
Installed: 0.5.7-3
apt-cache policy busybox|grep Installed:
Installed: 1:1.20.0-7
head -n3 ~/local/src/heirloom-sh/CHANGES:
Release ...
* A bug in the supplied realloc() replacement could result in heap
corruption. (No resulting failures have been observed with sh so far.)
Original bug report:
http://lists.gnu.org/archive/html/bug-bash/2014-03/msg00053.html
--
Eduardo Alan Bustamante López
next reply other threads:[~2014-03-12 15:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-12 15:36 Eduardo A. Bustamante López [this message]
2014-03-12 16:52 ` Bart Schaefer
2014-03-12 17:03 ` Peter Stephenson
2014-03-12 17:47 ` Eduardo A. Bustamante López
2014-03-12 17:49 ` Chet Ramey
2014-03-12 18:23 ` Peter Stephenson
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