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

[y6cmE]

呵呵，是提交两个自认为是bug及回复。不好意思，转发错了。可能大家对这没兴趣。：）
2006/2/12, Qiang (James) Li <shijialee at gmail.com>:
>
> 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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> > China-pm at pm.org
> > http://mail.pm.org/mailman/listinfo/china-pm
> >
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--
呵呵，Perl 初学者，大家多多照顾！
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