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[perl #119797] lvalue sub shows "Bizarre copy of ARRAY in block exit" in very specific case.

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From:
GlitchMr
Date:
September 15, 2013 10:08
Subject:
[perl #119797] lvalue sub shows "Bizarre copy of ARRAY in block exit" in very specific case.
Message ID:
rt-3.6.HEAD-1873-1379239696-271.119797-75-0@perl.org
# New Ticket Created by  GlitchMr 
# Please include the string:  [perl #119797]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=119797 >



This is a bug report for perl from glitchmr@myopera.com,
generated with the help of perlbug 1.39 running under perl 5.18.1.


-----------------------------------------------------------------
[Please describe your issue here]

Following code involving lvalue shows "Bizarre copy of ARRAY in block
exit". I've experimented with it, and it seems to happen with any
array (lexical or global), as long the `if` condition involves array
somehow, and returns false (for example, `if (@array, 0)`), and `else`
block returns `@array` without `return` keyword.

    # The subroutine has to be declared as lvalue, so you can write to
    # it in order to trigger the bug.
    sub array : lvalue {
        # This test has to involve @array somehow, but fail.
        if (@array) {
            # The contents of if block don't matter, so I left this
            # block empty. It just has to exist.
        }
        else {
            # The else condition has to return @array. Return keyword
            # cannot be used for this bug to trigger.
            @array;
        }
    }
    # Now, to trigger the bug, it's enough to write to array.
    (array) = ();

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
Site configuration information for perl 5.18.1:

Configured by nobody at Tue Aug 13 13:22:58 CEST 2013.

Summary of my perl5 (revision 5 version 18 subversion 1) configuration:
   
  Platform:
    osname=linux, osvers=3.10.5-1-arch,
    archname=x86_64-linux-thread-multi
    uname='linux mnt-chroots-arch-extra-x86_64-flo-64 3.10.5-1-arch #1
    smp preempt mon aug 5 08:04:22 cest 2013 x86_64 gnulinux '
    config_args='-des -Dusethreads -Duseshrplib -Doptimize=-march=x86-64
    -mtune=generic -O2 -pipe -fstack-protector --param=ssp-buffer-size=4
    -Dprefix=/usr -Dvendorprefix=/usr
    -Dprivlib=/usr/share/perl5/core_perl
    -Darchlib=/usr/lib/perl5/core_perl
    -Dsitelib=/usr/share/perl5/site_perl
    -Dsitearch=/usr/lib/perl5/site_perl
    -Dvendorlib=/usr/share/perl5/vendor_perl
    -Dvendorarch=/usr/lib/perl5/vendor_perl
    -Dscriptdir=/usr/bin/core_perl -Dsitescript=/usr/bin/site_perl
    -Dvendorscript=/usr/bin/vendor_perl -Dinc_version_list=none
    -Dman1ext=1perl -Dman3ext=3perl -Dcccdlflags='-fPIC'
    -Dlddlflags=-shared -Wl,-O1,--sort-common,--as-needed,-z,relro
    -Dldflags=-Wl,-O1,--sort-common,--as-needed,-z,relro'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing
    -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE
    -D_FILE_OFFSET_BITS=64',
    optimize='-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector
    --param=ssp-buffer-size=4',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe
    -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.8.1 20130725 (prerelease)',
    gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
    lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='cc', ldflags ='-Wl,-O1,--sort-common,--as-needed,-z,relro
    -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib/../lib /usr/lib/../lib /lib /usr/lib
    /lib64 /usr/lib64
    libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc
    -lgdbm_compat
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=/lib/libc-2.17.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.17'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E
    -Wl,-rpath,/usr/lib/perl5/core_perl/CORE'
    cccdlflags='-fPIC', lddlflags='-shared
    -Wl,-O1,--sort-common,--as-needed,-z,relro -L/usr/local/lib
    -fstack-protector'

Locally applied patches:
    

---
@INC for perl 5.18.1:
    /usr/lib/perl5/site_perl
    /usr/share/perl5/site_perl
    /usr/lib/perl5/vendor_perl
    /usr/share/perl5/vendor_perl
    /usr/lib/perl5/core_perl
    /usr/share/perl5/core_perl
    .

---
Environment for perl 5.18.1:
    HOME=/home/glitchmr
    LANG=pl_PL.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/bin
    PERL_BADLANG (unset)
    SHELL=/usr/bin/fish


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