# New Ticket Created by kynn jones
# Please include the string: [perl #36427]
# in the subject line of all future correspondence about this issue.
# <URL: https://rt.perl.org/rt3/Ticket/Display.html?id=36427 >
This is a bug report for perl from [EMAIL PROTECTED]
generated with the help of perlbug 1.35 running under perl v5.8.6.
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[Please enter your report here]
I first observed this behavior when attempting to save a directed
acyclic graph (DAG) consisting of of about 5,000 nodes, but below I
give a minimalistic example that exhibits the same behavior.
The following script creates a long sequence of nested references.
The command-line argument to the script should be a positive integer,
corresponding to the length of this sequence of references.
With an argument greater than some system-dependent critical size, the
script causes perl to segfault:
use strict;
use warnings;
my $size = shift;
my $x = [];
$x = [ $x ] for 1..$size;
require Storable;
Storable::store( \$x, '/tmp/$0.$$' ) or die;
warn "ok\n";
__END__
For this script, in the system described in this report, the critical
value of the argument is 30826. With any argument below this number,
the script terminates normally; with an argument greater than or equal
to it, perl segfaults.
Similarly, if the two lines indicated by the "# *" in the script above
are replaced by
require Data::Dumper;
Data::Dumper->Dump( [ \$x ] ) or die;
the resulting script fails for any argument greater than or equal to
15406.
Two important differences between the two versions of the script is
that the one using Storable fails after the 'warn "ok\n"' line, and
always terminates quickly (whether successfully or not), even for
values of the input close to the critical value. In contrast, for the
version using Data::Dumper, when the script fails the 'warn "ok\n"'
line never executes, and the time to success or failure grows sharply
as the value of the input approaches the critical value. But with the
DAG object that originally triggered the segfaulting, I observed this
pronounced slowing down near the critical input size with both
Data::Dumper and Storable.
Most likely the reason for the segfaulting is that a sufficiently long
chain of links will cause the serialization process to start
thrashing. Simply breaking the chain of links in two unconnected
halves allows the serialization to succeed, even though the total
number of links has been reduced by only 1.
[Please do not change anything below this line]
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---
Flags:
category=library
severity=medium
---
Site configuration information for perl v5.8.6:
Configured by kynn at Tue Apr 12 12:24:11 EDT 2005.
Summary of my perl5 (revision 5 version 8 subversion 6) configuration:
Platform:
osname=linux, osvers=2.4.18-686-smp, archname=i686-linux-ld
uname='linux luna 2.4.18-686-smp #1 smp sun apr 14 12:07:19 est 2002 i686
unknown '
config_args=''
hint=recommended, useposix=true, d_sigaction=define
usethreads=undef use5005threads=undef useithreads=undef
usemultiplicity=undef
useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
use64bitint=undef use64bitall=undef uselongdouble=define
usemymalloc=n, bincompat5005=undef
Compiler:
cc='cc', ccflags ='-fno-strict-aliasing -pipe -I/usr/local/include
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
optimize='-O2',
cppflags='-fno-strict-aliasing -pipe -I/usr/local/include'
ccversion='', gccversion='2.95.4 20011002 (Debian prerelease)',
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='long double', nvsize=12, Off_t='off_t',
lseeksize=8
alignbytes=4, prototype=define
Linker and Libraries:
ld='cc', ldflags =' -L/usr/local/lib'
libpth=/usr/local/lib /lib /usr/lib
libs=-lnsl -lgdbm -ldbm -ldb -ldl -lm -lcrypt -lutil -lc
perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
libc=/lib/libc-2.2.5.so, so=so, useshrplib=false, libperl=libperl.a
gnulibc_version='2.2.5'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'
Locally applied patches:
---
@INC for perl v5.8.6:
/home/kynn/local/lib/perl/my
/home/kynn/local/lib/perl/5.8.4
/home/kynn/local/lib/perl/5.6.1
/home/kynn/local/lib/perl5/5.8.6/i686-linux-ld
/home/kynn/local/lib/perl5/5.8.6
/home/kynn/local/lib/perl5/i686-linux-ld
/home/kynn/local/lib/perl5
/home/kynn/local/lib/perl5/5.8.6/i686-linux-ld
/home/kynn/local/lib/perl5/5.8.6
/home/kynn/local/lib/perl5/site_perl/5.8.6/i686-linux-ld
/home/kynn/local/lib/perl5/site_perl/5.8.6
/home/kynn/local/lib/perl5/site_perl
.
---
Environment for perl v5.8.6:
HOME=/home/kynn
LANG=C
LANGUAGE (unset)
LD_LIBRARY_PATH=/home/kynn/local/lib:/opt/java/jdk/lib/i386
LOGDIR (unset)
PATH=.:/home/kynn/local/bin:/home/kynn/local/usr/bin:/home/kynn/local/local/bin:/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin:/home/kynn/java/javacc/bin:/opt/java/jdk/bin:/usr/pbs/bin:/home/kynn/opt/ant/bin
PERL5LIB=/home/kynn/local/lib/perl/my:/home/kynn/local/lib/perl/5.8.4:/home/kynn/local/lib/perl/5.6.1:/home/kynn/local/lib/perl5
PERL5_CPANPLUS_CONFIG=/home/kynn/.cpanplus/config
PERL_BADLANG (unset)
SHELL=/usr/bin/zsh
