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Postings from February 2021
On Tue, 17 Nov 2020 at 02:32, <perl-bug@ton.iguana.be> wrote:
>
>
> This is a bug report for perl from perl-bug@ton.iguana.be,
> generated with the help of perlbug 1.42 running under perl 5.30.3.
>
>
> -----------------------------------------------------------------
> [Please describe your issue here]
>
> I reported it as a Carp bug, but there is some suspecious behaviour in the core
> around @DB::args going on (see later in the report).
>
> The version of Carp on my system is 1.50
>
> Consider the following program:
> ========================
> #!/usr/bin/perl -l
> package Foo;
> use Carp;
>
> sub bar {
> splice(@_, 0, 1);
> # die "Boom!";
> croak "Boom!";
> }
>
> package main;
> sub DESTROY { print "DESTROY" }
>
> {
> my $obj = bless [];
> eval { Foo::bar(undef, $obj)};
> print "ERR=$@";
> # @DB::args = ();
> # eval { Carp::croak "zz" };
> }
> print "END";
> ========================
>
> It creates an obkect $obj inside a lexical scope.
> This object should stop existing at the end of the scope, so it should print
> "DESTROY". After that the program should print the last line and say "END"
>
> So we expect:
> DESTROY
> END
>
> We however get:
> END
> DESTROY
>
> The object survived until global destruction.
>
> Uncommenting any of the commented out lines will make the program work as
> expected. Also commenting the "splice" statement will make things work.
>
> What is happening here is that the "croak" will call its internal "caller_info"
> sub which will use caller() inside package DB to populate @DB::args.
> (even though "croak" and "carp" mostly shouldn't need that).
>
> So the object ends up with an extra reference in @DB::args which makes it
> survive to the end of the program. That is why clearing @DB::args or doing
> another "croak" (which fill @DB::args with other data) fixes it. It also
> explains why "die" instead of "croak" fixes this.
This is an interesting bug. I do not think it really is in Carp, but
rather in how @Db::args is set up, the array should be localized
something like this:
local *Db::args= \@_;
So it should unwind when we exit the scope that the caller() was
executed in I think. Maybe Carp should be armored against this for now
however.
Yves
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