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Perl

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my ($ref1, $ref2, $ref3);
$ref1 = $ref2;
$ref2 = $ref3;
$ref3 = $ref1;

$ref1 $ref2 $ref3

reference counting
1

1

1
1 2

1

2 1

reference counting
1

0

1
1 2

1

2 1

reference counting
1

0

1
0 1

1

2 1

reference counting
1

0

1
0 1

1

1 1

reference counting
1

0

1
0 1 Leak

1

1 1

(1)

Template::Plugin::Filter
(TT-2.2)

Template::Plugin

return $self->{ _STATIC_FILTER } ||= sub {
$self->ﬁlter(shift);
};

(2)
AnyEvent

my $t; $t = AE::timer 1, 0, sub {
...;
undef $t;
};

$t sub { ... }

(2)
AnyEvent

...;
undef $t;
};

$t

(2)
AnyEvent

...;
undef $t;
};

(3)

my ($f, $x);
(sub { $f = sub { $x } })->();

OUTSIDE

sub {...} $f == sub { ... }

(3)
use Devel::Peek; Dump($f);

SV = IV(0x100827fd8) at 0x100827fe0
REFCNT = 2
RV = 0x100827878
SV = PVCV(0x10082b5f8) at 0x100827878
REFCNT = 1
GVGV::GV = 0x100856bc0 "main" :: "__ANON__"
OUTSIDE = 0x1008032a0 (ANON)
SV = PVCV(0x100852a90) at 0x1008032a0
REFCNT = 1
GVGV::GV = 0x100856bc0 "main" :: "__ANON__"
PADNAME = 0x1008277e8(0x100287000) PAD = 0x100827800(0x10025c0e0)
1. 0x100827fe0<2> FAKE "$f" ﬂags=0x0 index=1

1) ps
% perl
for (1 .. 10000) {
my $ref; $ref = $ref;

warn `ps -o rss= -p $$` if $_ % 1000 == 0;
}
1272
1304
1328
1352
1376
...

2) Test::LeakTrace
use Test::LeakTrace;
no_leaks_ok { my $ref; $ref = $ref };

2) Test::LeakTrace
use Test::LeakTrace;
no_leaks_ok { my $ref; $ref = $ref };

not ok 1 - leaks 1 <= 0
# Failed test 'leaks 1 <= 0'
# at - line 4.
# '1'
# <=
# '0'
# leaked REF(0x10083b610) from - line 4.
# SV = IV(0x10083b608) at 0x10083b610
# REFCNT = 1
# FLAGS = (PADMY,ROK)
# RV = 0x10083b610
# SV = IV(0x10083b608) at 0x10083b610
# REFCNT = 1
# RV = 0x10083b610
# SV = IV(0x10083b608) at 0x10083b610
# REFCNT = 1
# RV = 0x10083b610
# SV = IV(0x10083b608) at 0x10083b610
...

3) Devel::Cycle
use Devel::Cycle;

my ($ref1, $ref2, $ref3);
$ref1 = $ref2;
$ref2 = sub { $ref3 };
$ref3 = [$ref1];

ﬁnd_cycle($ref1);
Cycle (1):
$$A => &B
$B variable $ref3 => $C
$$C => @D
$D->[0] => $A

4) Devel::Leak::Object
use Devel::Leak::Object qw{GLOBAL_bless};
$Devel::Leak::Object::TRACKSOURCELINES = 1;

my $ref; $ref = bless $ref => "XXX";

Tracked objects by class:
XXX 1

Sources of leaks:
XXX
1 from - line: 3

5) DESTROY
sub Ref1::DESTROY { warn "destroyed REF1" }
sub Ref2::DESTROY { warn "destroyed REF2" }

my $x;
my $f = bless sub {
$x;
bless sub { $x } => "Ref2";
} => "Ref1";
$f->();

destroyed REF2 at - line 2.
destroyed REF1 at - line 1.

Devel::Gladiator

PASS (181) FAIL (436)

my $self = {name => "Hokkaido.pm", handler => undef};
$self->{handler} = sub {
print "Hello, ", $self->{name}, ".n";
};

$self->{handler}->();

sub { ... }

$self “Hokkaido.pm”

1)
undef $self;
};


sub { ... }


1)
undef $self;
};


sub { ... }

“Hokkaido.pm”

1)
undef $self;
};


1)

( )

($self->{handler} )

2) Scalar::Util::weaken
Scalar::Util::weaken(my $weaken_self = $self);
print "Hello, ", $weaken_self->{name}, ".n";
};


sub { ... }


2) Scalar::Util::weaken

Scalar::Util::weaken($self); #
};


3)
my $name = $self->{name};
print "Hello, ", $name, ".n";
};


sub { ... }


4)
my $self = shift;
};

$self->{handler}->($self);

sub { ... }


4)

AnyEvent::Handler

$hdl->push_read (line => sub {
my ($hdl, $line) = @_;
...
});

5) Data::Decycle

use Data::Decycle;
my $guard = Data::Decycle->new(
my $self = {name => "Hokkaido.pm", handler => undef}
);
"Hello, ", $self->{name}, ".n";
};


5) Data::Decycle

dankogai

guard

1)

:Perl 5.8.8

use Devel::Leak::Object qw{GLOBAL_bless};
bless my $x = {}, "Dummy";
(sub { sub { $x } })->();

Tracked objects by class:
Dummy 1

:Perl 5.8.8

my $x = bless {}, "Dummy";
(sub { $x; sub { $x } })->();

my $x = bless {}, "Dummy";
(sub { my $x = $x; sub { warn $x } })->();

:Obj-C ARC

retain release Perl

CBRFuture *future = [[CBRFuture alloc] init];
__weak CBRFuture *weakenFuture = future;
leftHandle(self, ^(id e) {
current = nil;
leftSend(weakenFuture, e);
});

:Obj-C Guard
NSString *local = @"OK";

static void changeLocalValue(BOOL willBreak) {
id original = local;
CBRGuard *guard = [[CBRGuard alloc] initGuard:^{
local = original;
}];

local = @"LOCALVALUE1";
}

:Obj-C Guard

autorelease

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