Zsh Mailing List Archive
Messages sorted by:
Reverse Date,
Date,
Thread,
Author
Re: Signal handling bugaboo in command substitution
On Mon, 07 Mar 2016 18:44:06 -0800
Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx> wrote:
> At a PS1 prompt:
>
> torch% print $(sleep 3; echo foo)
>
> Press ctrl+z during the sleep. Zsh is now hung, because the command
> substitution is occuring in prefork() so there's nothing to handle the
> stopped children and the parent itself ignores the signal. Zsh is hung;
> it won't return to a prompt, the command substitution will never produce
> the awaited output, and nothing (except "kill -CONT" from another shell)
> will wake it back up.
>
> I'm not sure what to do here. In other circumstances it's OK to stop a
> command substitution with a ctrl+z, and in any kind of non-interactive
> shell or even in a subshell the parent would handle the signal.
>
> Bash appears to leave TSTP blocked here when interactive. I don't think
> testing for interactivity is sufficient in zsh context, though.
How about something like this?
pws
diff --git a/Src/exec.c b/Src/exec.c
index b60fc90..caeb461 100644
--- a/Src/exec.c
+++ b/Src/exec.c
@@ -1001,9 +1001,21 @@ entersubsh(int flags)
* signals. If it is, we need to keep the special behaviour:
* see note about attachtty() above.
*/
- signal_default(SIGTTOU);
- signal_default(SIGTTIN);
- signal_default(SIGTSTP);
+ if (flags & ESUB_NOMONITOR)
+ {
+ /*
+ * Allowing any form of interactive signalling here is
+ * actively harmful as we are in a context where there is no
+ * control over the process.
+ */
+ signal_ignore(SIGTTOU);
+ signal_ignore(SIGTTIN);
+ signal_ignore(SIGTSTP);
+ } else {
+ signal_default(SIGTTOU);
+ signal_default(SIGTTIN);
+ signal_default(SIGTSTP);
+ }
}
if (interact) {
signal_default(SIGTERM);
Messages sorted by:
Reverse Date,
Date,
Thread,
Author