* Lincoln A. Baxter <[EMAIL PROTECTED]> [2004-01-12 10:02]:
> On Sun, 2004-01-11 at 15:50, Tim Bunce wrote:
> > It might also be worth adding some mechanism to integrate with Sys::Signal
> > http://search.cpan.org/src/DOUGM/Sys-Signal/Signal.pm
>
> I took a look that this. It is little bit of perlxs glue which
> uses perl's internals to set signal handlers, and have them
> restored when the object returned gets destroyed as it goes out
> of scope. It does not help us with our problem however, as it
> just does what perl does. I see no real benefit to this over:
>
> eval {
> local $SIG{ALRM} = sub { ... };
> }
>
> Perhaps there was a time when the above trick was not well
> known, and Sys::Signal was implemented to do that. After
> looking at the truss and strace outputs for the way the above
> code works, I would say that Sys::Signal is pretty unnecessary.
Actually, I think it is much worth pursuing, given this:
* Lincoln A. Baxter <[EMAIL PROTECTED]> [2004-01-11 15:19]:
> This module is almost as convenient to use as the above:
> #timeout a system call:
> use POSIX ':signal_h' ;
> use SignalHandler qw( set_handler );
>
> eval {
> local $SIG{ALRM};
> set_handler( 'mypackage::mysubname' ,SIGALRM );
> alarm(2)
> #... do something you want to timeout for instance:
> $dbh = DBI->connect( "dbi:Oracle:$dbn", $usr, $pwd
> ,{ AutoCommit=>$self->auto_commit()
> ,RaiseError=>1
> ,PrintError=>$self->print_err()
> } );
> alarm(0);
> };
> #perl clears the handler here... because of the local dec above
> alarm(0);
> if ( $@ ) ...
IMO it would be much neater not to have to separately localize
$SIG{ALRM} but to have restoration optionally done by your module
on request. I believe the clearest way to handle the syntax would
be a check for context in sig_set_handler() and returning an
object that auto-restores the signal in question on destruction
only if the context is not void.
That way people could write
my $restore = sig_set_handler( ... );
when they want it undone and simply
sig_set_handler( ... );
when they do want the change to persist until explicit change.
--
Regards,
Aristotle
"If you can't laugh at yourself, you don't take life seriously enough."
