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Postings from June 2010
El 31/05/2010 15:23, Tim Bunce escribió:
>
> I've occasionally used code like this:
>
> # exit with specific code when dieing from an uncaught exception
> $SIG{__DIE__} = sub {
> return if $^S; # we're inside an eval so ignore this one
> warn @_;
> exit 42;
> };
>
> Perhaps something like that is worth adding to the exit() docs.
Tim, I've been caught with more unexpectedness doing that: $^S can be undef.
BEGIN { eval { die 'X' } }
If the __DIE__ handler is installed: $^S will be undef, and you will
exit 42, even if the die was surrounded in eval {} !!! Modules like
Math::BigInt, or the perl debugger seem to do initializations in this
way so your __DIE__ exits on their CONTROLLED exceptions
In retrospective, I see that documentation from die mislead me a bit
(maybe it deserves a docpatch), and I didn'nt realize (although there is
a link to the doc on $^S) that I could be bitten.
http://perldoc.perl.org/functions/die.html says:
[QUOTE]
Although this feature was to be run only right before your program was
to exit, this is not currently so: the $SIG{__DIE__} hook is currently
called even inside eval()ed blocks/strings! If one wants the hook to do
nothing in such situations, put
1. die @_ if $^S;
as the first line of the handler (see $^S in perlvar).
[/QUOTE]
That statement is not quite true, as you won't propagate an exception in
a BEGIN block. You need an extra "die if (not defined $^S)".
Note: this all came from development of Nagios::Plugin::DieNicely.
There's a bit of background here:
http://www.pplusdomain.net/cgi-bin/blosxom.cgi/2010/05/28
My two cents,
Jose Luis Martinez
jlmartinez@capside.com
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