Debugging a problem

[azzazzello]

Hi guys,

I've been having a problem with a perl script that segfaults for a while now. I think I have a clue now however as to where or why it may be happening, but I need to debug it.

It is a threaded script. Perl version 5.8.3. I get the following error right after every thread returns.

Attempt to free unreferenced scalar: SV 0x83fa660 during global destruction.

The warning is surprising (for Perl) but rather obvious - to me it seems that there is a memory deallocation problem going on. How do I find out exactly what scalar SV 0x83fa660 is refering to? Here is my perl info.

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Summary of my perl5 (revision 5.0 version 8 subversion 3) configuration:
Platform:
osname=linux, osvers=2.6.0-1mdkenterprise, archname=i386-linux-thread-multi
uname='linux no.mandrakesoft.com 2.6.0-1mdkenterprise #1 smp thu dec 18 16:11:28 est 2003 i686 unknown unknown gnulinux '
config_args='-des -Dinc_version_list=5.8.2/i386-linux-thread-multi 5.8.2 5.8.1/i386-linux-thread-multi 5.8.1 5.8.0/i386-linux-thread-multi 5.8.0 5.6.1 5.6.0 -Darchname=i386-linux -Dcc=gcc -Doptimize=-O2 -fomit-frame-pointer -pipe -march=i586 -mcpu=pentiumpro -Dprefix=/usr -Dvendorprefix=/usr -Dsiteprefix=/usr -Dman3ext=3pm -Dcf_by=MandrakeSoft -Dmyhostname=localhost -Dperladmin=root@localhost -Dd_dosuid -Ud_csh -Duseshrplib -Dusethreads'
hint=recommended, useposix=true, d_sigaction=define
usethreads=define use5005threads=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='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
optimize='-O2 -fomit-frame-pointer -pipe -march=i586 -mcpu=pentiumpro ',
cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -fno-strict-aliasing -I/usr/local/include -I/usr/include/gdbm'
ccversion='', gccversion='3.3.2 (Mandrake Linux 10.0 3.3.2-4mdk)', 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='gcc', ldflags =' -L/usr/local/lib'
libpth=/usr/local/lib /lib /usr/lib
libs=-lnsl -lndbm -lgdbm -ldl -lm -lcrypt -lutil -lpthread -lc
perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
libc=/lib/libc-2.3.3.so, so=so, useshrplib=true, libperl=libperl.so
gnulibc_version='2.3.3'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic -Wl,-rpath,/usr/lib/perl5/5.8.3/i386-linux-thread-multi/CORE'
cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'


Characteristics of this binary (from libperl):
Compile-time options: MULTIPLICITY USE_ITHREADS USE_LARGE_FILES PERL_IMPLICIT_CONTEXT
Built under linux
Compiled at Feb 3 2004 13:50:20
@INC:
/usr/lib/perl5/5.8.3/i386-linux-thread-multi
/usr/lib/perl5/5.8.3
/usr/lib/perl5/site_perl/5.8.3/i386-linux-thread-multi
/usr/lib/perl5/site_perl/5.8.3
/usr/lib/perl5/site_perl
/usr/lib/perl5/vendor_perl/5.8.3/i386-linux-thread-multi
/usr/lib/perl5/vendor_perl/5.8.3
/usr/lib/perl5/vendor_perl/5.8.2/i386-linux-thread-multi
/usr/lib/perl5/vendor_perl/5.8.2
/usr/lib/perl5/vendor_perl/5.8.1/i386-linux-thread-multi
/usr/lib/perl5/vendor_perl/5.8.1
/usr/lib/perl5/vendor_perl

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I appreciate the help

 

[max1x]

- Are you using the -w swith and/or strict pragma.
- Have you tired the perl -d (perl debugger)