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Re: my $@ - a proposal

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On Fri, Jun 27, 2008 at 13:53:39 +0200, Abigail wrote:

> I've been wondering, I've used 
> 
>     eval { ... };
>     if ($@) {
>         ... whatever ...
>     }
> 
> for about dozen years,
> 
> and I cannot recall it ever not doing 'whatever' if the eval fails.

This happens if objects allocated within the eval { } have a DESTROY
that has an eval { } that doesn't fail.

This doesn't happen often, but when it does happen it's one of the
nastiest problems to debug, due to the fact that the code relates to
error handling, and the fact that the invocation is implicit.

> Having said that, I think that any fix should target the
> 
>     eval { ... };
>     if ($@) { ... }
> 
> case. That's how the majority of the people think exceptions work, and they
> will continue to code this way. 

Agreed

Making local $@/die DWIM like the previous thread mentioned makes
writing defensive that doesn't break this easier

A lexical $@ makes this even easier,

	my $@;
	eval { ... }
	if ($@) { ... }

is 100% safe no matter what for that particular error (no local $@
can touch that particular $@)

It would be interesting to find a way for 'use 5.012' code to
automatically create a lexical $@, similarly to how $1, $2 etc are
treated

-- 
  Yuval Kogman <nothingmuch@woobling.org>
https://nothingmuch.woobling.org  0xEBD27418

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• my $@ - a proposal by Yuval Kogman
• RE: my $@ - a proposal by Jan Dubois
• Re: my $@ - a proposal by David Nicol
• Re: my $@ - a proposal by Graham Barr
• Re: my $@ - a proposal by David Nicol
• Re: my $@ - a proposal by Mark Mielke
• RE: my $@ - a proposal by Jan Dubois
• Re: my $@ - a proposal by Graham Barr
• Re: my $@ - a proposal by Graham Barr
• RE: my $@ - a proposal by Jan Dubois
• Re: my $@ - a proposal by Ben Morrow
• Re: my $@ - a proposal by Graham Barr
• RE: my $@ - a proposal by Jan Dubois
• Re: my $@ - a proposal by David Nicol
• RE: my $@ - a proposal by Jan Dubois
• Re: my $@ - a proposal by David Nicol
• RE: my $@ - a proposal by Jan Dubois
• Re: my $@ - a proposal by David Golden
• Re: my $@ - a proposal by Johan Vromans
• Re: my $@ - a proposal by Mark Mielke
• Re: my $@ - a proposal by Rafael Garcia-Suarez
• Re: my $@ - a proposal by Mark Mielke
• Re: my $@ - a proposal by Ben Morrow
• Re: my $@ - a proposal by Elliot Shank
• Re: my $@ - a proposal by Abigail
• Re: my $@ - a proposal by Juerd Waalboer
• Re: my $@ - a proposal by David Golden
• Re: my $@ - a proposal by Yuval Kogman
• Re: my $@ - a proposal by David Golden
• Re: my $@ - a proposal by Graham Barr
• Re: my $@ - a proposal by Yuval Kogman
• Re: my $@ - a proposal by Graham Barr
• Re: my $@ - a proposal by Sam Vilain
• Re: my $@ - a proposal by David Nicol
• Re: my $@ - a proposal by David Golden
• Re: my $@ - a proposal by Graham Barr
• Re: my $@ - a proposal by David Nicol
• RE: my $@ - a proposal by Jan Dubois
• Re: my $@ - a proposal by Aristotle Pagaltzis
• Re: my $@ - a proposal by Mark Mielke
• Re: my $@ - a proposal by Raphael_Manfredi
• Re: my $@ - a proposal by Mark Mielke
• Re: my $@ - a proposal by Raphael_Manfredi
• Re: my $@ - a proposal by Abigail
• Re: my $@ - a proposal by Mark Mielke
• Re: my $@ - a proposal by David Golden
• Re: my $@ - a proposal by Raphael_Manfredi
• Re: my $@ - a proposal by Dr.Ruud
• Re: my $@ - a proposal by Yuval Kogman
• Re: my $@ - a proposal by Sam Vilain
• Re: my $@ - a proposal by Abigail
• Re: my $@ - a proposal by Yuval Kogman
• Re: my $@ - a proposal by Sean O'Rourke
• Re: my $@ - a proposal by Yuval Kogman
• Re: my $@ - a proposal by Steffen Mueller
• Re: my $@ - a proposal by Yuval Kogman
• Re: my $@ - a proposal by David Golden
• Re: my $@ - a proposal by Yuval Kogman
• Re: my $@ - a proposal by David Golden
• Re: my $@ - a proposal by Abigail
• Re: my $@ - a proposal by Aristotle Pagaltzis
• Re: my $@ - a proposal by Mark Mielke
• Re: my $@ - a proposal by Yuval Kogman
• Re: my $@ - a proposal by Dr.Ruud
• Re: my $@ - a proposal by Mark Mielke
• Re: my $@ - a proposal by Sam Vilain
• Re: my $@ - a proposal by David Cantrell
• Re: my $@ - a proposal by Sam Vilain
• Re: my $@ - a proposal by Moritz Lenz
• Re: my $@ - a proposal by Sam Vilain
• Re: my $@ - a proposal by Moritz Lenz
• Re: my $@ - a proposal by Sam Vilain
• Re: my $@ - a proposal by Moritz Lenz
• Re: my $@ - a proposal by Sam Vilain
• Re: my $@ - a proposal by Abigail
• Re: my $@ - a proposal by Mark Mielke
• Re: my $@ - a proposal by Aristotle Pagaltzis
• Re: my $@ - a proposal by David Nicol
• Re: my $@ - a proposal by Nicholas Clark
• Re: my $@ - a proposal by David Nicol
• RE: my $@ - a proposal by Jan Dubois
• Re: my $@ - a proposal by David Nicol
• Re: my $@ - a proposal by Reini Urban
• Re: my $@ - a proposal by Dr.Ruud
• Re: my $@ - a proposal by Sam Vilain