Re: using features in a Safe compartment

Hi! First of all, "reval" only evaluates the code and then returns the value. So in this case, the following will work:

use warnings;
use strict;
use Safe;
use feature qw{say};

say "Hello!";

my $cft = Safe->new;

$cft->deny_only();

my $ret = $dft->reval(qq{return "Hello Again!"}, undef);

say $ret;
[download]

So using the "say" doesn't work because it evaluates to nothing, and returns nothing. In fact, I was kind of surprised that it didn't at least return "1" since say should return "true". But who knows.

Update: something else just occurred to me. Safe is not going to evaluate the "use" or in this case what I tried below. It evaluates the entire script, doesn't recognize the "say" keyword and throws the error. It never *executes* the use or the require/import.

my $unsafe = qq|
     require feature;
     feature->import( qw{say switch} );
     say "Hope this works";
     return "I did what you said";
|;
# explicit load of feature, but doesn't work (unexpected result)
 
$ret = $cft->reval( $unsafe, undef );
[download]

HTH,
Tyler.

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Re^2: using features in a Safe compartment by djerius (Beadle) on Mar 22, 2011 at 04:09 UTC
I'm afraid I don't really understand your first point: "reval" only evaluates the code and then returns the value. So using the "say" doesn't work because it evaluates to nothing, and returns nothing. As my example showed, the code is never evaluated because it fails to compile due to `say` not being recognized. My attempt at enabling the feature in the Safe compartment via `use feature` doesn't work. It works in a standard eval: `$ perl -e 'eval q[use feature qw[ say ]; say "hello"]' hello` [download] The code in your update shows the same problem that I'm struggling with, namely that `use feature` is not enabling the feature in the Safe compartment. Perhaps I should rephrase the question: how does one get `use feature` to work in a Safe compartment?	[reply] [d/l] [select]

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Re^2: using features in a Safe compartment
by djerius (Beadle) on Mar 22, 2011 at 04:09 UTC

"reval" only evaluates the code and then returns the value.
So using the "say" doesn't work because it evaluates to nothing, and returns nothing.

say

Safe

use feature

It works in a standard eval:

$ perl -e 'eval q[use feature qw[ say ]; say "hello"]'
hello
[download]

use feature

Perhaps I should rephrase the question: how does one get use feature to work in a Safe compartment?

[reply]
[d/l]
[select]