[perl #27010] tie doesn't autoviv an aliased hash element

# New Ticket Created by  andrew@pimlott.net 
# Please include the string:  [perl #27010]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org:80/rt3/Ticket/Display.html?id=27010 >



This is a bug report for perl from andrew@pimlott.net,
generated with the help of perlbug 1.34 running under perl v5.8.2.


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[Please enter your report here]

The following amusing function works:

    sub assign { $_[0] = $_[1] }
    assign $foo => 1;
    assign $foo{bar} => 1;

In particular, in the last line, the hash element is autovivified by the
assignment to the alias $_[0].  The following doesn't:

    sub maitai { tie $_[0] => 'MaiTai' }
    maitai $foo;        # ok
    maitai $foo{bar};   # not ok

$foo gets tied as expected, but $foo{bar} doesn't.  Evidently, whatever got
tied was dissociated from the hash element.  This can be repaired with

    sub maitai { tie $_[0], 'MaiTai' }
    $foo{bar} = undef;
    maitai $foo{bar};   # ok

However, this doesn't do it:

    sub maitai { $_[0] = 'DUMMY'; tie $_[0], 'MaiTai' }
    maitai $foo{bar};   # $foo{bar} eq 'DUMMY' !!

Last,

    tie $foo{bar} => 'MaiTai';

works fine.  So the problem appears to be autovivifying, through an alias,
in tie.  It would be cool if this worked.

Here is a tie implementation to test with:

    package MaiTai;
    sub TIESCALAR { bless {} => MaiTai; }
    sub FETCH { 'TIED' }

Andrew

[Please do not change anything below this line]
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---
Flags:
    category=core
    severity=low
---
Site configuration information for perl v5.8.2:

Configured by Debian Project at Sat Nov 15 18:33:34 EST 2003.

Summary of my perl5 (revision 5.0 version 8 subversion 2) configuration:
  Platform:
    osname=linux, osvers=2.4.22-xfs+ti1211, archname=i386-linux-thread-multi
    uname='linux kosh 2.4.22-xfs+ti1211 #1 sat oct 25 10:11:37 est 2003 i686 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=i386-linux -Dprefix=/usr -Dprivlib=/usr/share/perl/5.8.2 -Darchlib=/usr/lib/perl/5.8.2 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.8.2 -Dsitearch=/usr/local/lib/perl/5.8.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Uusesfio -Uusenm -Duseshrplib -Dlibperl=libperl.so.5.8.2 -Dd_dosuid -des'
    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='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O3',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -fno-strict-aliasing -I/usr/local/include'
    ccversion='', gccversion='3.3.2 (Debian)', 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 =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=/lib/libc-2.3.2.so, so=so, useshrplib=true, libperl=libperl.so.5.8.2
    gnulibc_version='2.3.2'
  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 v5.8.2:
    /home/pimlott/lib/perl
    /home/pimlott/local/lib/perl
    /etc/perl
    /usr/local/lib/perl/5.8.2
    /usr/local/share/perl/5.8.2
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.8.2
    /usr/share/perl/5.8.2
    /usr/local/lib/site_perl
    .

---
Environment for perl v5.8.2:
    HOME=/home/pimlott
    LANG=en_US
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/atria/bin:/usr/sbin:/sbin:/home/pimlott/bin:/usr/local/atria/bin:/usr/sbin:/sbin:/home/pimlott/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games
    PERL5LIB=/home/pimlott/lib/perl:/home/pimlott/local/lib/perl
    PERL_BADLANG (unset)
    SHELL=/bin/zsh

• [perl #27010] tie doesn't autoviv an aliased hash element by perlbug-followup
• Re: [perl #27010] tie doesn't autoviv an aliased hash element by Yitzchak Scott-Thoennes