[PerlChina] [perl #38346] [PATCH] Re: B::Deparse's bug?

[Qiang (James) Li]

I don't really know what you are talking about. wrong mailing list?  :)

Qiang

On 2/11/06, y6cmE <refile at gmail.com> wrote:
> PerlAPP's bug?
> I try the PDK 530.
> example:
> ###  test.pl
> {
>     package XXX;
>     use YYY;
>     @XXX::ISA=qw(YYY);
>     sub new {
>          .......
>     }
>     sub ....
>
> }
> my $test=new XXX;
> ...
> ### test.pl
> and run PerlAPP test.pl
> it print :
> Can't locate XXX.pm in @INC...........
>
> 2006/2/9, y6cmE <refile at gmail.com>:
> >
> >
> >
> > ---------- Forwarded message ----------
> > From: Stephen McCamant via RT < perlbug-followup at perl.org>
> > Date: 2006-2-9 上午9:51
> > Subject: [perl #38346] [PATCH] Re: B::Deparse's bug?
> > To: refile at gmail.com
> >
> > >>>>> "RS" == Robert Spier < rspier at pobox.com> writes:
> >
> > RS> Perl5 Bug Summary
> >
> > RS> New issues that have not been responded to yet
> > RS> 1 - 2 weeks old
> > RS> 38346 B::Deparse's bug?
> >
> > I don't remember ever seeing this on p5p, perhaps because it was
> > sent to perlbug-admin instead of perlbug.
> >
> > Here's a further-simplified test case:
> >
> > % perl -MO=Deparse -e '$a ? $b = $c : $d = $e'
> > $a ? ($b = $c) : $d = $e;
> > % perl -MO=Deparse -e '$a ? $b = $c : $d = $e' | perl -c
> > Assignment to both a list and a scalar at - line 1, near "$e;"
> >
> > I vaguely recall this issue coming up before, but maybe it was
> > somewhere else, or maybe it was just about how Perl parses and I never
> > thought to check what Deparse does. The precedence of ?: is a bit
> > weird because for the middle argument, the ? and the : act a bit like
> > parentheses: potentially, you could have a very low precedence
> > operator there without causing an ambiguity. For instance, the only
> > reasonable interpretation of:
> >
> > $a ? $b or $c : $d
> >
> > is
> >
> > $a ? ($b or $c) : $d
> >
> > even though "or" normally has lower precedence than ?:. However,
> > perl's grammar doesn't allow the unparenthesized "or" example: the
> > lowest precedence operators that can be in the middle of a ?: without
> > parens are assignments. I'm not sure how intentional this was, but it
> > seems pretty defensible on language design grounds, since mixing ?:
> > with low-precedence operators is error-prone and rarely necessary.
> >
> > As for the current bug, Deparse is excessively conservative in adding
> > parentheses, applying the same rule to the middle arg as to the left
> > or right args. Alas, perl takes the parens as signifying a list,
> > leading to the error shown. The right fix appears to be to make
> > Deparse less conservative, as in the appended patch.
> >
> > By the way, the original reporter may already know this, but in case
> > they don't and for the benefit of anyone else playing along at home,
> > the original example doesn't do what it looks like it's supposed to,
> > exactly because of a precedence problem. To demonstrate with Deparse:
> >
> > % perl -MO=Deparse,-p -e '$a ? $b = $c : $d = $e'
> > (($a ? ($b = $c) : $d) = $e);
> >
> > What the author of the code presumably meant was:
> >
> > % perl -MO=Deparse,-p -e '$a ? $b = $c : ($d = $e)'
> > ($a ? ($b = $c) : ($d = $e));
> >
> > (especially since in the original example, $b and $d were the same
> > variable).
> >
> > -- Stephen
> >
> > --- perl-current/ext/B/B/Deparse.pm     2006-01-03
> 04:38:52.000000000 -0500
> > +++ perl at 26919/ext/B/B/Deparse.pm       2006-02-08 20:19:17.147191075
> -0500
> > @@ -2504,7 +2504,7 @@ sub pp_cond_expr {
> >            (is_scope($false) || is_ifelse_cont($false))
> >            and $self->{'expand'} < 7) {
> >        $cond = $self->deparse($cond, 8);
> > -       $true = $self->deparse($true, 8);
> > +       $true = $self->deparse($true, 6);
> >        $false = $self->deparse($false, 8);
> >        return $self->maybe_parens("$cond ? $true : $false", $cx, 8);
> >     }
> >
> >
> >
> >
> > --
> > 呵呵，Perl 初学者，大家多多照顾！
>
>
>
> --
> 呵呵，Perl 初学者，大家多多照顾！
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