循環参照の見つけ方と直し方の話

1. 2011.12.10 hiratara

2. d.hatena.ne.jp/hiratara
twitter.com/hiratara
Perl
YAPC gihyo.jp

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

5. GC
Perl GC

6. mark-and-sweep GC

7. mark-and-sweep GC

8. mark-and-sweep GC

9. mark-and-sweep GC

10. reference counting
1
1
1
1 2
1
2 1

11. reference counting
1
0
1
1 2
1
2 1

12. reference counting
1
0
1
0 1
1
2 1

13. reference counting
1
0
1
0 1
1
1 1

14. reference counting
1
0
1
0 1 Leak
1
1 1

15. (1)
Template::Plugin::Filter
(TT-2.2)
Template::Plugin
return $self->{ _STATIC_FILTER } ||= sub {
$self->filter(shift);
};

16. (2)
AnyEvent
my $t; $t = AE::timer 1, 0, sub {
...;
undef $t;
};
$t sub { ... }

17. (2)
AnyEvent
my $t; $t = AE::timer 1, 0, sub {
...;
undef $t;
};
$t sub { ... }

18. (2)
AnyEvent
my $t; $t = AE::timer 1, 0, sub {
...;
undef $t;
};
$t

19. (2)
AnyEvent
my $t; $t = AE::timer 1, 0, sub {
...;
undef $t;
};
$t

20. (2)
AnyEvent
my $t; $t = AE::timer 1, 0, sub {
...;
undef $t;
};

21. (3)
my ($f, $x);
(sub { $f = sub { $x } })->();
OUTSIDE
sub {...} $f == sub { ... }

22. (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

23. 5
( ≒ )

24. 1) ps
% perl
for (1 .. 10000) {
my $ref; $ref = $ref;
warn `ps -o rss= -p $$` if $_ % 1000 == 0;
}
1272
1304
1328
1352
1376
...

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

26. 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
# FLAGS = (PADMY,ROK)
# RV = 0x10083b610
# SV = IV(0x10083b608) at 0x10083b610
# REFCNT = 1
# FLAGS = (PADMY,ROK)
# RV = 0x10083b610
# SV = IV(0x10083b608) at 0x10083b610
...

27. 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

28. 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

29. 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.

30. Devel::Gladiator
PASS (181) FAIL (436)

31. 5

32. $self sub { ... }

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

34. 1)
my $self = {name => "Hokkaido.pm", handler => undef};
$self->{handler} = sub {
print "Hello, ", $self->{name}, ".n";
undef $self;
};
$self->{handler}->();
sub { ... }
$self “Hokkaido.pm”

35. 1)
my $self = {name => "Hokkaido.pm", handler => undef};
$self->{handler} = sub {
print "Hello, ", $self->{name}, ".n";
undef $self;
};
$self->{handler}->();
sub { ... }
$self “Hokkaido.pm”

36. 1)
my $self = {name => "Hokkaido.pm", handler => undef};
$self->{handler} = sub {
print "Hello, ", $self->{name}, ".n";
undef $self;
};
$self->{handler}->();
sub { ... }
“Hokkaido.pm”

37. 1)
my $self = {name => "Hokkaido.pm", handler => undef};
$self->{handler} = sub {
print "Hello, ", $self->{name}, ".n";
undef $self;
};
$self->{handler}->();
sub { ... }
“Hokkaido.pm”

38. 1)
my $self = {name => "Hokkaido.pm", handler => undef};
$self->{handler} = sub {
print "Hello, ", $self->{name}, ".n";
undef $self;
};
$self->{handler}->();

39. 1)
( )
($self->{handler} )

40. 2) Scalar::Util::weaken
my $self = {name => "Hokkaido.pm", handler => undef};
Scalar::Util::weaken(my $weaken_self = $self);
$self->{handler} = sub {
print "Hello, ", $weaken_self->{name}, ".n";
};
$self->{handler}->();
sub { ... }
$self “Hokkaido.pm”

41. 2) Scalar::Util::weaken
my $self = {name => "Hokkaido.pm", handler => undef};
Scalar::Util::weaken($self); #
$self->{handler} = sub {
print "Hello, ", $self->{name}, ".n";
};
$self->{handler}->();

42. 3)
my $self = {name => "Hokkaido.pm", handler => undef};
my $name = $self->{name};
$self->{handler} = sub {
print "Hello, ", $name, ".n";
};
$self->{handler}->();
sub { ... }
$self “Hokkaido.pm”

43. 4)
my $self = {name => "Hokkaido.pm", handler => undef};
$self->{handler} = sub {
my $self = shift;
print "Hello, ", $self->{name}, ".n";
};
$self->{handler}->($self);
sub { ... }
$self “Hokkaido.pm”

44. 4)
AnyEvent::Handler
$hdl->push_read (line => sub {
my ($hdl, $line) = @_;
...
});

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

46. 5) Data::Decycle
dankogai
guard
1)

48. :Perl 5.8.8
use Devel::Leak::Object qw{GLOBAL_bless};
bless my $x = {}, "Dummy";
(sub { sub { $x } })->();
Tracked objects by class:
Dummy 1

49. :Perl 5.8.8
my $x = bless {}, "Dummy";
(sub { $x; sub { $x } })->();
my $x = bless {}, "Dummy";
(sub { my $x = $x; sub { warn $x } })->();

51. :Obj-C ARC
retain release Perl
CBRFuture *future = [[CBRFuture alloc] init];
__weak CBRFuture *weakenFuture = future;
leftHandle(self, ^(id e) {
current = nil;
leftSend(weakenFuture, e);
});

52. :Obj-C Guard
NSString *local = @"OK";
static void changeLocalValue(BOOL willBreak) {
id original = local;
CBRGuard *guard = [[CBRGuard alloc] initGuard:^{
local = original;
}];
local = @"LOCALVALUE1";
}

53. :Obj-C Guard
autorelease