On 3/3/14 7:47 AM, konsolebox wrote:
> On Wed, Feb 19, 2014 at 11:01 PM, Chet Ramey <chet.ra...@case.edu
> <mailto:chet.ra...@case.edu>> wrote:
>
> On 2/19/14 1:51 AM, konsolebox wrote:
>
> > Bash-4.3 handles signals and traps when a read run by the read
> builtin is
> > interrupted by a signal. I'm not sure that's the best thing to
> do,
> > since traps should really be run when commands finish, but we're
> going to
> > try it.
> >
> > Since bash-4.2, bash has installed its SIGCHLD signal handler with
> > SA_RESTART, so a child death does not unexpectedly interrupt
> system calls.
> > There were several bug reports concerning this. So yes, SIGCHLD is
> > special.
> >
> >
> > I'm not really able to comprehend the significance of SA_RESTART to
> SIGCHLD
> > that it could affect the signal and make it behave differently from the
> > other signals i.e. it can't be a good idea to allow interruption from it
> > when in a read builtin context, but could it be possible that we allow
> it
> > when not in posix mode? Probably it's about the variable
> posixly_correct.
> > If we can allow at least just one interruption to happen maybe with the
> > help of the variable running_trap it would really be good enough.
>
> SIGCHLD is different from other signals in that it can arrive at any time
> without user intervention. Say you run a background process that exits
> during a call to the read builtin. Should it interrupt the read? What
> would be gained by having system calls return errors because bash reaps a
> child? Should it interrupt the read only if there is a trap set?
>
> There's a way to do what you want, but the question is whether or not the
> demand is sufficient to make SIGCHLD traps run when other traps would not.
>
>
> I tried to use my script again with the new release of bash (4.3). Almost
> every signal was allowed besides SIGCHLD (17). SIGALRM (19) seems
> reasonable not to be included since it's used by read. SIGKILL (9) and
> SIGCONT (19) which I excluded from it I doubt are reasonable to be caught.
I made no changes in this area. It was far too late in the bash-4.3
release cycle. There is commented-out code in lib/sh/zread.c for you
to play around with, but it is not enabled by default in bash-4.3.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU c...@case.edu http://cnswww.cns.cwru.edu/~chet/
