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[ID 20000928.004] mysterious extra refcount in debugger

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From:
pimlott
Date:
September 28, 2000 22:47
Subject:
[ID 20000928.004] mysterious extra refcount in debugger
Message ID:
m13etMu-000SEmC@nolfolan.idiomtech.com
This is a bug report for perl from pimlott@nolfolan.idiomtech.com,
generated with the help of perlbug 1.26 running under perl 5.00503.


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

I found that, under the debugger only, an object wasn't getting destroyed
when expected.  Using Devel::Peek, I found that the object had a mysterious
extra reference under the debugger.  I worked it down to a minimal test
case, but I'm still baffled so I won't even guess at the cause.

    package Foo;

    sub mydo { &{$_[0]} }

    sub new {
        my $self = {};
        mydo sub { $self };  # This is the culprit; no idea why
        return bless $self => 'Foo';
    }
    sub DESTROY { warn "destroying\n"; }

    package main;

    $foo = new Foo;
    warn "one down\n";
    $foo = new Foo;
    warn "two down\n";

When run normally, this prints

    one down
    destroying
    two down
    destroying

as expected.  But under the debugger, the destructors are not run until
after the program ends and I quit the debugger.  Devel::Peek tells me that,
after the first "new Foo" line, %$foo has 2 references under the debugger,
instead of the normal 1.  However, right before the return statement in new,
$self has only one reference.  Somehow, it picks up the extra reference in
the process of returning from new--but only under the debugger.

Please tell me if there's anything else I can do to help, as I'm very
bothered by this bug.  (It's making it difficult for me to debug a program
under the debugger, since resources are not freed and so it eventually
crashes.)

Also duplicated on 5.005_03 on Solaris 2.7.

Thanks,
Andrew

[Please do not change anything below this line]
-----------------------------------------------------------------

---
Site configuration information for perl 5.00503:

Configured by drow at Sun Apr 30 12:07:23 EDT 2000.

Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration:
  Platform:
    osname=linux, osvers=2.2.15pre14, archname=i386-linux
    uname='linux them 2.2.15pre14 #2 smp mon mar 13 14:29:00 est 2000 i686 unknown '
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef useperlio=undef d_sfio=undef
  Compiler:
    cc='cc', optimize='-O2 ', gccversion=2.95.2 20000313 (Debian GNU/Linux)
    cppflags='-Dbool=char -DHAS_BOOL -D_REENTRANT -DDEBIAN -I/usr/local/include'
    ccflags ='-Dbool=char -DHAS_BOOL -D_REENTRANT -DDEBIAN -I/usr/local/include'
    stdchar='char', d_stdstdio=undef, usevfork=false
    intsize=4, longsize=4, ptrsize=4, doublesize=8
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -lndbm -lgdbm -ldbm -ldb -ldl -lm -lc -lposix -lcrypt
    libc=, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:
    

---
@INC for perl 5.00503:
    /home/pimlott/idiom/perl
    /usr/lib/perl5/5.005/i386-linux
    /usr/lib/perl5/5.005
    /usr/local/lib/site_perl/i386-linux
    /usr/local/lib/site_perl
    /usr/lib/perl5
    .

---
Environment for perl 5.00503:
    HOME=/home/pimlott
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/pimlott/bin:/usr/local/atria/bin:/usr/sbin:/sbin:/home/pimlott/bin:/usr/local/atria/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games
    PERL5LIB=/home/pimlott/idiom/perl
    PERL_BADLANG (unset)
    SHELL=/usr/bin/zsh


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