in reply to Re: Need Unused Variable Warning Msgs
in thread Need Unused Variable Warning Msgs

It would fail on a simple piece of code like this: 
    {my $var;}
    {my $var;}

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Both variables are unused. "Unused" would mean only declared in a certain scope, not only declared in the entire program.

Abigail

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Re: Re: Need Unused Variable Warning Msgs
by samtregar (Abbot) on Jun 10, 2002 at 17:14 UTC
    Writing a regex that parses Perl scopes is left as an exercise for the reader. Ultimately that's what tools like lint have done for C - they actually parse the C code just like a compiler would and do pattern matching to find bad code.

    -sam

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      Parsing C is orders of magnitude simpler than Perl. Not even perl can always pass Perl.

      But even if you have such a regex, to actually find out whether a variable is unused or not, you've got to know what a piece of code will do. To determine that at compile time, you need to solve the halting problem.

      If you solve the halting problem, I'll do the regex.

      Abigail

[reply]
        So how does lint do it? Does it solve the halting problem? I think it would be sufficient to determine if a variable as created in a scope with my() or our() and then never mentioned in the scope again. That would be useful enough to be worth the occaisonal false-positive that would result from evals and other nefarious tricks.

        -sam

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