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[perl #130649] Threads, shared memory, blessed objects fail to call->DESTROY method
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From:
V Burns
Date:
January 26, 2017 14:02
Subject:
[perl #130649] Threads, shared memory, blessed objects fail to call->DESTROY method
Message ID:
rt-4.0.24-11114-1485434330-1009.130649-75-0@perl.org
# New Ticket Created by V Burns
# Please include the string: [perl #130649]
# in the subject line of all future correspondence about this issue.
# <URL: https://rt.perl.org/Ticket/Display.html?id=130649 >
This is a bug report for Perl from victor.burns@bankofamerica.com,
generated with the help of perlbug 1.39 running under perl 5.12.2.
-----------------------------------------------------------------
[Please describe your issue here]
This issue is believed to exist in all 5.10.1+ Perl's and every older Perl as well.
I have verified the issue in every Perl I have at my disposal from 5.10.1, 5.12.0, 5.22.0 and 5.24.0.
Description:
If the last reference to an object is in thread shared memory the objects
DESTROY method won't be called or highly unlikely to be called. This is a
*huge* problem for applications that are OO and designed using composition
of other classes (HAS-A). The last, and possibly only reference will be in
Perl's thread shared memory. I think the real issue only resembles my
description and therefore it is not perfect. I have however included a
small script that when used and modified as the comments suggest the
related behaviors may be observed. The actual issue is a bit more
unpredictable.
## PERL BUG Example
use 5.010001;
use strict;
use warnings;
use threads;
use threads::shared;
our $VERSION = 0.1;
say 'Hello World!, - Perl shared memory failure to call ->DESTROY detector.';
LEAKER:
{
## Using the "shared" attribute can play a role in this
## Best guess it means all references are shared.
my $aa :shared = bless &share({}), 'Lazy::Crazy';
my $bb :shared = bless &share({}), 'Lazy::Crazy';
my $cc :shared = &share( bless {}, 'Lazy::Crazy' );
## Placing an object into another makes it a sure bet its
## ->DESTROY won't be called
$aa->{ has_c } = $cc;
$bb->{ has_a } = $aa;
## It's strange that the order of the following assignments
## will allow the last one touched to call its ->DESTROY
$cc->{ label } = 'c';
$aa->{ label } = 'a';
$bb->{ label } = 'b';
## If I'm able to control the order these are unwrapped (destroyed)
## things start working as expected.
## How likely can I always get this right, not at all!
## (uncomment and things work as expected)
# $bb = undef;
# $aa = undef;
# $cc = undef;
}
package Lazy::Crazy;
sub DESTROY
{
my $self = shift;
printf "# %s '%s' is destroyed\n", ref $self, $self->{ label };
return;
}
## END
[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
category=library
severity=high
module=threads::shared
---
Site configuration information for perl 5.12.2:
Configured by SYSTEM at Mon Sep 6 23:12:49 2010.
Summary of my perl5 (revision 5 version 12 subversion 2) configuration:
Platform:
osname=MSWin32, osvers=5.00, archname=MSWin32-x86-multi-thread
uname=''
config_args='undef'
hint=recommended, useposix=true, d_sigaction=undef
useithreads=define, usemultiplicity=define
useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
use64bitint=undef, use64bitall=undef, uselongdouble=undef
usemymalloc=n, bincompat5005=undef
Compiler:
cc='cl', ccflags ='-nologo -GF -W3 -MD -Zi -DNDEBUG -O1 -DWIN32 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DUSE_SITECUSTOMIZE -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DUSE_PERLIO -D_USE_32BIT_TIME_T -DPERL_MSVCRT_READFIX',
optimize='-MD -Zi -DNDEBUG -O1',
cppflags='-DWIN32'
ccversion='12.00.8804', gccversion='', gccosandvers=''
intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=8
ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='__int64', lseeksize=8
alignbytes=8, prototype=define
Linker and Libraries:
ld='link', ldflags ='-nologo -nodefaultlib -debug -opt:ref,icf -libpath:"C:\Program Files (x86)\Perl\lib\CORE" -machine:x86'
libpth=\lib
libs= oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib netapi32.lib uuid.lib ws2_32.lib mpr.lib winmm.lib version.lib odbc32.lib odbccp32.lib comctl32.lib msvcrt.lib
perllibs= oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib netapi32.lib uuid.lib ws2_32.lib mpr.lib winmm.lib version.lib odbc32.lib odbccp32.lib comctl32.lib msvcrt.lib
libc=msvcrt.lib, so=dll, useshrplib=true, libperl=perl512.lib
gnulibc_version=''
Dynamic Linking:
dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -debug -opt:ref,icf -libpath:"C:\Program Files (x86)\Perl\lib\CORE" -machine:x86'
Locally applied patches:
ACTIVEPERL_LOCAL_PATCHES_ENTRY
1fd8fa4 Add Wolfram Humann to AUTHORS
f120055 make string-append on win32 100 times faster
a2a8d15 Define _USE_32BIT_TIME_T for VC6 and VC7
007cfe1 Don't pretend to support really old VC++ compilers
6d8f7c9 Get rid of obsolete PerlCRT.dll support
d956618 Make Term::ReadLine::findConsole fall back to STDIN if /dev/tty can't be opened
321e50c Escape patch strings before embedding them in patchlevel.h
---
@INC for perl 5.12.2:
C:/Program Files (x86)/Perl/site/lib
C:/Program Files (x86)/Perl/lib
.
---
Environment for perl 5.12.2:
HOME (unset)
LANG (unset)
LANGUAGE (unset)
LD_LIBRARY_PATH (unset)
LOGDIR (unset)
PATH=C:\ProgramData\Oracle\Java\javapath;C:\Oracle\product\11.2.0\client_1\bin;C:\Program Files (x86)\Perl\site\bin;C:\Program Files (x86)\Perl\bin;C:\windows\system32;C:\windows;C:\windows\System32\Wbem;C:\windows\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\PKWARE\pkzipc;C:\Program Files (x86)\Microsoft Application Virtualization Client;C:\Program Files (x86)\SSH Communications Security\SSH Tectia\SSH Tectia AUX;C:\Program Files (x86)\SSH Communications Security\SSH Tectia\SSH Tectia AUX\Support binaries;C:\Program Files (x86)\SSH Communications Security\SSH Tectia\SSH Tectia Broker;C:\Program Files (x86)\SSH Communications Security\SSH Tectia\SSH Tectia Client;C:\windows\System32\WindowsPowerShell\v1.0\;C:\Program Files\1E\NomadBranch\
PERL_BADLANG (unset)
SHELL (unset)
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