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Postings from June 2008
"Joshua ben Jore" schreef:
> Dr.Ruud:
>> Joshua ben Jore:
>>> Semi-recently at work I found that a few buggy exception objects in
>>> the global $@ were clearing themselves out of $@ as a side effect of
>>> examining them for truth.
>>
>> Oops, I'd better change my
>>
>> push @errors, $@ if $@;
>>
>> to something like
>>
>> {my $e; push @errors, $e if $e = $@}
>
> No, that's only if you have exception objects which might also have
> overloading.
This was about any kind, so including those.
> Also, you can only trust $@ as long as you also trust
> that you'll never have objects around that can clear $@ during their
> DESTROY phase. The presence of objects which can set $@ during their
> DESTROY means your evail{} can fail and $@ can be empty afterwards.
> It's why you have to actually return something from eval or assign
> success out somewhere.
>
> For "95%" of perl code, trusting that $@ is an ok boolean works. For
> the other 5%, set phasers to kill and raise all shields.
>
> my $ok = eval { ...; return 1};
> unless( $ok ) {
> my $e = $@;
> ...
> }
I tend to write that as an "or":
eval {
...
1;
} or {
my $e = $@;
printf LOG "[%s] %s\n", scalar localtime, $e;
};
which could also look more like
{ my @errors;
push @errors, $@ if $@;
eval {
push @errors, $@ if $@;
...
1;
} or {
push @errors, $@;
};
die @errors if @errors;
}
--
Affijn, Ruud
"Gewoon is een tijger."
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