Marc Herbert wrote:
> Chet Ramey a écrit :
>> Marc Herbert wrote:
>>> The following script crashes bash versions 2.05, 3.2.25, 4.0.16,...
>>>
>>>
>>> trap "echo USR1caught" USR1
>>> read -t 1
>>> foo=$( kill -USR1 $$ )
>>> echo 'Yeah! no Segmentation fault!'
>> Thanks for the report.
>
> Thanks for bash in the first place.
>
>
>> Fixed in the next version.
>
> Chet, is there any workaround for existing versions?
Sure. There's the usual idiom. It's unusual to see a script that uses
command substitution for this. Most existing scripts use simple
subshells to do it, whether (command) or asynchronous commands using `&'.
In general, if you want to do something like set an alarm to go off in
the future, say after 10 seconds, you do something like
{ sleep 10; kill -USR1 $$; } &
and perform a potentially blocking operation.
> I mean, there must be some memory corruption involved in here, so is it
> possible to dodge it without upgrading? For instance, would simply avoiding
> the "-t" option of "read" be enough to guarantee no memory corruption? Other?
> Thanks a lot in advance!
It's a combination of the assignment statement and the trap handling.
Yes, there is memory corruption that occurs, because the trap handler
doesn't unwind-protect a global variable used by the expansion and
execution code.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
Chet Ramey, ITS, CWRU c...@case.edu http://cnswww.cns.cwru.edu/~chet/
