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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:
James E Keenan via RT
Date:
September 15, 2013 13:21
Subject:
[perl #119797] lvalue sub shows "Bizarre copy of ARRAY in block exit" in very specific case.
Message ID:
rt-3.6.HEAD-1873-1379251260-963.119797-15-0@perl.org
On Sun Sep 15 03:08:16 2013, glitchmr@myopera.com wrote:
>
> 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) = ();
>
1. I cannot reproduce the error you cite. I cannot generate this error:
""Bizarre copy of ARRAY in block exit".
2. Did you try running your program with 'use strict; use warnings;'?
If so, you would have gotten messages that indicated problematic code.
3. Did you try rewriting your program to name the subroutine something
other than 'array'? That only made for a more confusing bug report.
Once I started to debug this with steps 2 and 3 above, I found that I
could get an executable (though not very useful) program by simply
placing '()' after the subroutine call.
##########
$ cat 119797-lvalue.pl
my @this = (1..5);
(that()) = ();
print "@this\n";
sub that :lvalue { if (@this) { } else { @this; } }
##########
$ perl 119797-lvalue.pl
1 2 3 4 5
##########
I don't think there is a bug here.
> [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
---
via perlbug: queue: perl5 status: new
https://rt.perl.org:443/rt3/Ticket/Display.html?id=119797
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