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thread constructor with arguments can leak #9969

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p5pRT opened this issue Nov 17, 2009 · 9 comments
Closed

thread constructor with arguments can leak #9969

p5pRT opened this issue Nov 17, 2009 · 9 comments
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@p5pRT
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@p5pRT p5pRT commented Nov 17, 2009

Migrated from rt.perl.org#70602 (status was 'resolved')

Searchable as RT70602$

@p5pRT
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@p5pRT p5pRT commented Nov 17, 2009

From @ikegami

Created by @ikegami

The following code has Perl saying "Scalars leaked​: 1" numerous times.

----BEGIN CODE----
use strict;
use warnings;

use threads;

sub PINGIT {
  print "PINGIT\n";
  return 0;
}

sub THPING {
  #@​_ = (); # FIX 2
  print "THPING\n";
  my @​th;
  for (1..5) {
  push @​th, threads->create(\&PINGIT);
  }
  $_->join for @​th;
  return 0;
}

{
  my %opts;
  my @​th;
  for (1..2) {
  push @​th, threads->create(\&THPING, \%opts);
  #push @​th, threads->create(\&THPING); # FIX 1
  }
  $_->join for @​th;
}
----END CODE----

----BEGIN OUTPUT----
THPING
PINGIT
PINGIT
THPING
PINGIT
PINGIT
PINGIT
Scalars leaked​: 1
Scalars leaked​: 1
PINGIT
PINGIT
PINGIT
Scalars leaked​: 1
PINGIT
Scalars leaked​: 1
Scalars leaked​: 1
Scalars leaked​: 1
Scalars leaked​: 1
PINGIT
Scalars leaked​: 1
Scalars leaked​: 1
Scalars leaked​: 1
----END OUTPUT----

The leak goes away if no additional arguments are passed to ->create. The
leak goes also goes away if @​_ is emptied inside
the thread functions.

Perl Info

Flags:
    category=library
    severity=medium

The problem is not specific to a version of Perl (reproduced on 5.8.0,
5.8.8, 5.10.0 and 5.10.1).
The problem is not specific to an OS (reproduced on WinXP and Linux).

@p5pRT
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@p5pRT p5pRT commented Nov 18, 2009

From @jdhedden

The following code has Perl saying "Scalars leaked​: 1" numerous times.

This is another example of a known 'threads' problem involving leaked
scalars caused by temporary stack variables.

Dave Mitchell is has looked at this issue, but does not have a fix.

This bug report and bug reports 41138, 41816 and 66108 (and possibly
others) should be combined.

@p5pRT
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@p5pRT p5pRT commented Nov 18, 2009

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

@p5pRT
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@p5pRT p5pRT commented Dec 1, 2009

From @dk

Created by @dk

The code below produces warning "Scalars leaked​: 1". It does so on
blead and 5.10.1, both on win32 and linux.

use threads;
our $X;

sub moo
{
  local $X;
  async {}-> join;
}

moo($X);

Perl Info

Flags:
    category=core
    severity=medium

Site configuration information for perl 5.11.0:

Summary of my perl5 (revision 5 version 11 subversion 0) configuration:
  Commit id: 0f289c68de322445a34feb41ea8f00b7bf9c85de
  Platform:
    osname=linux, osvers=2.6.31-14-generic, archname=i686-linux-thread-multi
    uname='linux wallace 2.6.31-14-generic #48-ubuntu smp fri oct 16 14:04:26 ut
c 2009 i686 gnulinux '
    config_args=''
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=undef, use64bitall=undef, uselongdouble=undef
    useemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.4.1', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib /usr/lib64
    libs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=/lib/libc-2.10.1.so, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.10.1'
 Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector'

Characteristics of this binary (from libperl): 
  Compile-time options: MULTIPLICITY PERL_DONT_CREATE_GVSV
                        PERL_IMPLICIT_CONTEXT PERL_MALLOC_WRAP USE_ITHREADS
                        USE_LARGE_FILES USE_PERLIO USE_REENTRANT_API
  Built under linux
  Compiled at Dec  1 2009 16:06:32
  @INC:
    lib
    /usr/local/lib/perl5/site_perl/5.11.0/i686-linux-thread-multi
    /usr/local/lib/perl5/site_perl/5.11.0
    /usr/local/lib/perl5/5.11.0/i686-linux-thread-multi
    /usr/local/lib/perl5/5.11.0
    .

--
Environment for perl 5.10.1:
    HOME=/home/dk
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/dk/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/X11R6/bin:/usr/local/site/bin:/usr/local/site/sbin:/home/dk/bin
    PERL_BADLANG (unset)
    SHELL=/usr/bin/zsh

@p5pRT
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@p5pRT p5pRT commented Dec 2, 2009

From @obra

The code below produces warning "Scalars leaked​: 1". It does so on
blead and 5.10.1, both on win32 and linux.

use threads;
our $X;

sub moo
{
local $X;
async {}-> join;
}

moo($X);

And it does on Debian's 5.8.8 (Linux x86) as well.

@p5pRT
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@p5pRT p5pRT commented Dec 2, 2009

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

@p5pRT
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@p5pRT p5pRT commented Dec 2, 2009

From @ikegami

On Tue, Dec 1, 2009 at 10​:29 AM, Dmitry Karasik
<perlbug-followup@​perl.org>wrote​:

# New Ticket Created by Dmitry Karasik
# Please include the string​: [perl #70974]
# in the subject line of all future correspondence about this issue.
# <URL​: http​://rt.perl.org/rt3/Ticket/Display.html?id=70974 >

This is a bug report for perl from dmitry@​karasik.eu.org,
generated with the help of perlbug 1.36 running under perl 5.10.0.

-----------------------------------------------------------------
[Please enter your report here]

The code below produces warning "Scalars leaked​: 1". It does so on
blead and 5.10.1, both on win32 and linux.

use threads;
our $X;

sub moo
{
local $X;
async {}-> join;
}

moo($X);

It's a case of a known problem. The workaround is to add @​_=(); in moo().

type 70974.pl
use threads;
our $X;

sub moo
{
  @​_=() if $ARGV[0];
  local $X;
  async {}-> join;
}

moo($X);

perl 70974.pl 0
Scalars leaked​: 1

perl 70974.pl 1

This is the same problem as the one reported in
http​://rt.perl.org/rt3/Ticket/Display.html?id=70602 and others before it.
(Some are listed in a comment to 70602.)

@p5pRT
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@p5pRT p5pRT commented Jan 11, 2010

From @iabyn

Fixed in blead with e81cd4d

@p5pRT
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@p5pRT p5pRT commented Jan 11, 2010

@iabyn - Status changed from 'open' to 'resolved'

@p5pRT p5pRT closed this Jan 11, 2010
@p5pRT p5pRT added the Severity Low label Oct 18, 2019
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