Conrad, Bill (ThomasTech) <> wrote:
> Hi All
>
> If I have some Perl code in a variable $code and I use and
> eval($code) to execute the code can I do something like
>
> sub x {
> my ( $code
> , $other_stuff
> ) @_ ;
>
> my %save_sym = %main:: ;
>
> eval($code) ;
>
> %main:: = %save_sym ;
>
> }
>
> to remove any symbols created within the code from the symbol table?
> Is this a good practice or is there a better way?
Apart from the times when it is unavoidable, block evals are preferable
to string evals. Unless you have complete control over the string being
eval-ed it can represent a rather large security hole.
Regarding saving the symbol table. It is not just the removal of symbols
created, but modification of existing symbols that may need taking care
of. Also, copying a hash just copies keys and values. If the any values
are references, only the reference is copied, not what it refers to, so
the reverse copy will not restore the state of that object after the
eval. Don't forget that lexical variables don't appear in the symbol
table, so you symbol table copy will not restore any changes made to in
scope variables made in the eval.
There a re probably lots of other problems too.
Sounds pretty dodgy to me. Perhaps if you said what you were trying to
accomplish by this it might be easier for someone to suggest a better
way.
HTH
--
Brian Raven
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