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DESTROY called twice on objects created in threads #11686

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p5pRT opened this issue Oct 6, 2011 · 5 comments
Closed

DESTROY called twice on objects created in threads #11686

p5pRT opened this issue Oct 6, 2011 · 5 comments

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@p5pRT
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p5pRT commented Oct 6, 2011

Migrated from rt.perl.org#100840 (status was 'rejected')

Searchable as RT100840$
@p5pRT
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p5pRT commented Oct 6, 2011

From @jdhedden

Created by @jdhedden

The bug is that when a thread creates an object and then
exits, the object's DESTROY method is being called twice​:
First in the thread where it was created, and then again in
the main thread.

In contrast, if the object is destroyed before the thread
exits (for example, undef($obj)), DESTROY is only called
once (as should be the case).

The attached script demonstrates this above. Here is the output​:

  Object created in thread 1
  Okay​: Object created in thread 1 was destroyed in thread 1
  BUG​: Object created in thread 1 but destroyed in thread 0

  Object created in thread 2
  Okay​: Object created in thread 2 was destroyed in thread 2

This occurs in all versions of the threads module (1.09 -
1.85) that I tested with this version of Perl (5.10.1 under
Cygwin on Windows).

Perl Info 

Flags:
    category=library
    severity=high
    module=threads

Site configuration information for perl 5.10.1:

Configured by rurban at Sat Aug 28 20:14:06 CEST 2010.

Summary of my perl5 (revision 5 version 10 subversion 1) configuration:

  Platform:
    osname=cygwin, osvers=1.7.5(0.22553),
archname=i686-cygwin-thread-multi-64int
    uname='cygwin_nt-5.1 reini 1.7.5(0.22553) 2010-04-12 19:07 i686 cygwin '
    config_args='-de -Dlibperl=cygperl5_10.dll -Dcc=gcc-4 -Dld=g++-4
-Dmksymlinks -Dusethreads -Dmad=y -Doptimize=-O3 -Accflags=-g3'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=undef, uselongdouble=undef
    usemymalloc=y, bincompat5005=undef
  Compiler:
    cc='gcc-4', ccflags ='-DPERL_USE_SAFE_PUTENV -U__STRICT_ANSI__ -g3
-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include',
    optimize='-O3',
    cppflags='-DPERL_USE_SAFE_PUTENV -U__STRICT_ANSI__ -g3
-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.3.4 20090804 (release) 1', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long long', ivsize=8, nvtype='double', nvsize=8,
Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='g++-4', ldflags =' -Wl,--enable-auto-import
-Wl,--export-all-symbols -Wl,--stack,8388608
-Wl,--enable-auto-image-base -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib /lib
    libs=-lgdbm -ldb -ldl -lcrypt -lgdbm_compat
    perllibs=-ldl -lcrypt
    libc=/usr/lib/libc.a, so=dll, useshrplib=true, libperl=cygperl5_10.dll
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags=' --shared  -Wl,--enable-auto-import
-Wl,--export-all-symbols -Wl,--stack,8388608
-Wl,--enable-auto-image-base -L/usr/local/lib -fstack-protector'

Locally applied patches:
    CYG11 no-bs
    CYG12 no archlib in otherlibdirs
    CYG14 Dynaloader
    CYG15 static-Win32CORE
    CYG17 utf8-paths
    CYG21 LibList-Kid.patch
    CYG22 cygwin-1.7 hints
    CYG23 544-stat
    CYG24 build man pages
    CYG25 rebase_privlib
    Module-Build-0.36_13
    Bug#55162 CYG18 File::Spec::case_tolerant performance
    disable ExtUtils::MakeMaker::Coverage in Sys-Syslog


@INC for perl 5.10.1:
    /usr/lib/perl5/5.10/i686-cygwin
    /usr/lib/perl5/5.10
    /usr/lib/perl5/site_perl/5.10/i686-cygwin
    /usr/lib/perl5/site_perl/5.10
    /usr/lib/perl5/vendor_perl/5.10/i686-cygwin
    /usr/lib/perl5/vendor_perl/5.10
    /usr/lib/perl5/vendor_perl/5.10
    /usr/lib/perl5/site_perl/5.8
    /usr/lib/perl5/vendor_perl/5.8
    .


Environment for perl 5.10.1:
    CYGWIN=nodosfilewarning
    HOME=/home/heddenj
    LANG=C
    LANGUAGE=C
    LC_ALL=C
    LD_LIBRARY_PATH=/usr/local/lib:/usr/lib
    LOGDIR (unset)
    PATH=/home/heddenj/bin:/usr/local/src/perl/bin:/usr/local/bin:/usr/bin:/c/Progra~1/Java/jre6/bin:/c/WINDOWS/system32:/c/WINDOWS:/c/WINDOWS/System32/Wbem:/c/Program
Files/ATI Technologies/ATI.ACE/Core-Static:/c/Program
Files/TortoiseSVN/bin:/c/PYTHON27:/c/Program Files/MySQL/MySQL Server
5.5/bin:/c/WINDOWS/system32/WindowsPowerShell/v1.0:.
    PERLIO=perlio
    PERL_BADLANG (unset)
    SHELL (unset)

@p5pRT
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p5pRT commented Oct 6, 2011

From @jdhedden

bug.pl

@p5pRT
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p5pRT commented Oct 6, 2011

From @ikegami

sub func {
  my $obj = Foo->new();
}

is functionally the same as

sub func {
  return my $obj = Foo->new();
}

which is effectively the same as

sub func {
  return Foo->new();
}

In order for join() to return this value, it needs to be cloned. $obj gets
cloned, the original gets destroyed, and the clone is returned by join()
where it is destroyed. Fix​:

sub func {
  my $obj = Foo->new();
  1;
}

This isn't a bug.

@p5pRT
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p5pRT commented Oct 6, 2011

The RT System itself - Status changed from 'new' to 'open'

@p5pRT
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p5pRT commented Nov 6, 2011

@cpansprout - Status changed from 'open' to 'rejected'

@p5pRT p5pRT closed this as completed Nov 6, 2011
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