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[perl #5664] Bug in weak references

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From:
Steve Peters via RT
Date:
December 23, 2006 09:00
Subject:
[perl #5664] Bug in weak references
Message ID:
rt-3.6.HEAD-1774-1166893239-981.5664-15-0@perl.org
On Thu Feb 01 23:25:52 2001, me-01@ton.iguana.be wrote:
> 
> -----------------------------------------------------------------
> [Please enter your report here]
> 
> perl -wle 'use Data::Dumper; use WeakRef; $foo = [1]; $baz=$foo; push
>    @baz, weaken($foo); print Dumper \@baz; print Dumper $foo;'
> 
> @baz will be unexpectedly empty.
> (PS: why do I not get a warning that I use $baz only once ?)
> 
> [Please do not change anything below this line]
> -----------------------------------------------------------------
> ---
> Flags:
>     category=core
>     severity=low
> ---
> Site configuration information for perl v5.6.0:
> 
> Configured by ton at Wed Aug  9 23:24:07 CEST 2000.
> 
> Summary of my perl5 (revision 5.0 version 6 subversion 0)
>    configuration:
>   Platform:
>     osname=linux, osvers=2.4.0-test5, archname=i686-linux
>     uname='linux quasar 2.4.0-test5 #2 sat jul 29 04:45:14 cest 2000
>    i686 unknown '
>     config_args=''
>     hint=recommended, useposix=true, d_sigaction=define
>     usethreads=undef use5005threads=undef useithreads=undef
>    usemultiplicity=undef
>     useperlio=undef d_sfio=undef uselargefiles=undef
>     use64bitint=undef use64bitall=undef uselongdouble=undef
>    usesocks=undef
>   Compiler:
>     cc='cc', optimize='-O2 -fomit-frame-pointer', gccversion=egcs-
>    2.91.66 19990314 (egcs-1.1.2 release), gccosandvers=
>     cppflags='-fno-strict-aliasing -I/usr/local/include'
>     ccflags ='-fno-strict-aliasing -I/usr/local/include'
>     stdchar='char', d_stdstdio=define, usevfork=false
>     intsize=4, longsize=4, ptrsize=4, doublesize=8
>     d_longlong=define, longlongsize=8, d_longdbl=define,
>    longdblsize=12
>     ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
>    lseeksize=4
>     alignbytes=4, usemymalloc=y, prototype=define
>   Linker and Libraries:
>     ld='cc', ldflags =' -L/usr/local/lib -L/opt/gnu/lib'
>     libpth=/usr/local/lib /opt/gnu/lib /lib /usr/lib
>     libs=-lnsl -lndbm -ldl -lm -lc -lposix -lcrypt -lutil
>     libc=/lib/libc-2.1.1.so, so=so, useshrplib=true,
>    libperl=libperl.so
>   Dynamic Linking:
>     dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-
>    rdynamic -Wl,-rpath,/usr/lib/perl5/5.6.0/i686-linux/CORE'
>     cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib
>    -L/opt/gnu/lib'
> 
> Locally applied patches:
> 
> 
> ---
> @INC for perl v5.6.0:
>     /usr/lib/perl5/5.6.0/i686-linux
>     /usr/lib/perl5/5.6.0
>     /usr/lib/perl5/site_perl/5.6.0/i686-linux
>     /usr/lib/perl5/site_perl/5.6.0
>     /usr/lib/perl5/site_perl
>     .
> 
> ---
> Environment for perl v5.6.0:
>     HOME=/home/ton
>     LANG (unset)
>     LANGUAGE (unset)
>     LD_LIBRARY_PATH (unset)
>     LOGDIR (unset)
>    
PATH=/home/ton/bin.Linux:/home/ton/bin:/home/ton/bin.SampleSetup:/usr/local/bin:/usr/local/sbin:/usr/local/jre/bin:/usr/local/jdk116_v5/bin:/home/oracle/product/8.1.5/bin:/usr/games/bin:/usr/X11R6/bin:/usr/share/bin:/usr/bin:/usr/sbin:/bin:/sbin:.
>     PERL_BADLANG (unset)
>     SHELL=/bin/bash

I'm guessing WeakRef is the predecessor to Scalar::Util.  Replacing with
Scalar::Util, I get similar results.

steve@enterprise:~> perl -wle 'use Data::Dumper; use Scalar::Util
qw(weaken); $foo = [1]; $baz=$foo; push @baz, weaken($foo); print Dumper
\@baz; print Dumper $foo;'
$VAR1 = [];

$VAR1 = [
          1
        ];



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