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[perl #122322] OOK hack example in perlguts is outdated with COW
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From:
Niko Tyni
Date:
July 18, 2014 06:58
Subject:
[perl #122322] OOK hack example in perlguts is outdated with COW
Message ID:
rt-4.0.18-10295-1405666683-1678.122322-75-0@perl.org
# New Ticket Created by Niko Tyni
# Please include the string: [perl #122322]
# in the subject line of all future correspondence about this issue.
# <URL: https://rt.perl.org/Ticket/Display.html?id=122322 >
This is a bug report for perl from Niko Tyni <ntyni@debian.org>,
generated with the help of perlbug 1.39 running under perl 5.18.2.
-----------------------------------------------------------------
Trying to fix Devel-Size [rt.cpan.org #95493] for Perl 5.20,
I ran into the following:
% perl5182 -MDevel::Peek -le '$a="12345"; $a=~s/.//; Dump($a)'
SV = PV(0x25b4a50) at 0x25d5720
REFCNT = 1
FLAGS = (POK,OOK,pPOK)
OFFSET = 1
PV = 0x25cebe1 ( "\1" . ) "2345"\0
CUR = 4
LEN = 15
% perl5200 -MDevel::Peek -le '$a="12345"; $a=~s/.//; Dump($a)'
SV = PV(0x1179a90) at 0x11951d8
REFCNT = 1
FLAGS = (POK,pPOK)
PV = 0x118f9e0 "2345"\0
CUR = 4
LEN = 10
This changed with commit v5.19.0-246-g13b0f67, "re-enable Copy-on-Write
by default." Clearly COW stops the OOK hack triggering in this specific
case.
The example is from the 'Offsets' section in perlguts, so at least that
needs updating. For the benefit of that, and also Devel-Size, is there
another simple way to trigger the OOK hack noawadays? I couldn't come
up with one yet.
-----------------------------------------------------------------
---
Flags:
category=core
severity=low
---
Site configuration information for perl 5.18.2:
Configured by Debian Project at Mon Jul 14 20:39:08 UTC 2014.
Summary of my perl5 (revision 5 version 18 subversion 2) configuration:
Platform:
osname=linux, osvers=3.14-1-amd64, archname=x86_64-linux-gnu-thread-multi
uname='linux estella 3.14-1-amd64 #1 smp debian 3.14.10-1 (2014-07-07) x86_64 gnulinux '
config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -fwrapv -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Dldflags= -Wl,-z,relro -Dlddlflags=-shared -Wl,-z,relro -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.18 -Darchlib=/usr/lib/perl/5.18 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.18.2 -Dsitearch=/usr/local/lib/perl/5.18.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -Uversiononly -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dlibperl=libperl.so.5.18.2 -des'
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 -DDEBIAN -fwrapv -fstack-protector -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
optimize='-O2 -g',
cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -fstack-protector -fno-strict-aliasing -pipe -I/usr/local/include'
ccversion='', gccversion='4.9.0', 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 =' -fstack-protector -L/usr/local/lib'
libpth=/usr/local/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /usr/lib
libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
perllibs=-ldl -lm -lpthread -lc -lcrypt
libc=, so=so, useshrplib=true, libperl=libperl.so.5.18.2
gnulibc_version='2.19'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib -fstack-protector'
Locally applied patches:
DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
DEBPKG:debian/db_file_ver - http://bugs.debian.org/340047 Remove overly restrictive DB_File version check.
DEBPKG:debian/doc_info - Replace generic man(1) instructions with Debian-specific information.
DEBPKG:debian/enc2xs_inc - http://bugs.debian.org/290336 Tweak enc2xs to follow symlinks and ignore missing @INC directories.
DEBPKG:debian/errno_ver - http://bugs.debian.org/343351 Remove Errno version check due to upgrade problems with long-running processes.
DEBPKG:debian/libperl_embed_doc - http://bugs.debian.org/186778 Note that libperl-dev package is required for embedded linking
DEBPKG:fixes/respect_umask - Respect umask during installation
DEBPKG:debian/writable_site_dirs - Set umask approproately for site install directories
DEBPKG:debian/extutils_set_libperl_path - EU:MM: Set location of libperl.a to /usr/lib
DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or perllocal.pod for perl or vendor
DEBPKG:debian/prefix_changes - Fiddle with *PREFIX and variables written to the makefile
DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to the binary targets.
DEBPKG:debian/instmodsh_doc - Debian policy doesn't install .packlist files for core or vendor.
DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH as per Debian policy.
DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to /etc/perl/Net as /usr may not be writable.
DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
DEBPKG:debian/module_build_man_extensions - http://bugs.debian.org/479460 Adjust Module::Build manual page extensions for the Debian Perl policy
DEBPKG:debian/prune_libs - http://bugs.debian.org/128355 Prune the list of libraries wanted to what we actually need.
DEBPKG:fixes/net_smtp_docs - [rt.cpan.org #36038] http://bugs.debian.org/100195 Document the Net::SMTP 'Port' option
DEBPKG:debian/perlivp - http://bugs.debian.org/510895 Make perlivp skip include directories in /usr/local
DEBPKG:debian/cpanplus_definstalldirs - http://bugs.debian.org/533707 Configure CPANPLUS to use the site directories by default.
DEBPKG:debian/cpanplus_config_path - Save local versions of CPANPLUS::Config::System into /etc/perl.
DEBPKG:debian/deprecate-with-apt - http://bugs.debian.org/702096 Point users to Debian packages of deprecated core modules
DEBPKG:debian/squelch-locale-warnings - http://bugs.debian.org/508764 Squelch locale warnings in Debian package maintainer scripts
DEBPKG:debian/skip-upstream-git-tests - Skip tests specific to the upstream Git repository
DEBPKG:debian/patchlevel - http://bugs.debian.org/567489 List packaged patches for 5.18.2-7 in patchlevel.h
DEBPKG:debian/skip-kfreebsd-crash - http://bugs.debian.org/628493 [perl #96272] Skip a crashing test case in t/op/threads.t on GNU/kFreeBSD
DEBPKG:fixes/document_makemaker_ccflags - http://bugs.debian.org/628522 [rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
DEBPKG:debian/find_html2text - http://bugs.debian.org/640479 Configure CPAN::Distribution with correct name of html2text
DEBPKG:debian/hurd_test_skip_stack - http://bugs.debian.org/650175 Disable failing GNU/Hurd tests dist/threads/t/stack.t
DEBPKG:fixes/manpage_name_Test-Harness - http://bugs.debian.org/650451 [rt.cpan.org #73399] cpan/Test-Harness: add NAME headings in modules with POD
DEBPKG:debian/makemaker-pasthru - http://bugs.debian.org/660195 [rt.cpan.org #28632] Make EU::MM pass LD through to recursive Makefile.PL invocations
DEBPKG:debian/perl5db-x-terminal-emulator.patch - http://bugs.debian.org/668490 Invoke x-terminal-emulator rather than xterm in perl5db.pl
DEBPKG:debian/cpan-missing-site-dirs - http://bugs.debian.org/688842 Fix CPAN::FirstTime defaults with nonexisting site dirs if a parent is writable
DEBPKG:fixes/memoize_storable_nstore - [rt.cpan.org #77790] http://bugs.debian.org/587650 Memoize::Storable: respect 'nstore' option not respected
DEBPKG:fixes/net_ftp_failed_command - [rt.cpan.org #37700] http://bugs.debian.org/491062 Net::FTP: cope gracefully with a failed command
DEBPKG:fixes/perlbug-patchlist - [3541c11] http://bugs.debian.org/710842 [perl #118433] Make perlbug look up the list of local patches at run time
DEBPKG:fixes/module_metadata_security_doc - [68cdd4b] CVE-2013-1437 documentation fix
DEBPKG:fixes/module_metadata_taint_fix - [bff978f] http://bugs.debian.org/722210 [rt.cpan.org #88576] untaint version, if needed, in Module::Metadata
DEBPKG:fixes/IPC-SysV-spelling - http://bugs.debian.org/730558 [rt.cpan.org #86736] Fix spelling of IPC_CREAT in IPC-SysV documentation
DEBPKG:fixes/goto-sub-crash - [bfa371b] http://bugs.debian.org/736187 [perl #119949] Stop undef *_, goto &sub from crashing
DEBPKG:debian/regcomp-mips-optim - http://bugs.debian.org/754054 Downgrade the optimization of regcomp.c on mips due to a gcc-4.9 bug
---
@INC for perl 5.18.2:
/etc/perl
/usr/local/lib/perl/5.18.2
/usr/local/share/perl/5.18.2
/usr/lib/perl5
/usr/share/perl5
/usr/lib/perl/5.18
/usr/share/perl/5.18
/usr/local/lib/site_perl
.
---
Environment for perl 5.18.2:
HOME=/home/niko
LANG=en_US.UTF-8
LANGUAGE (unset)
LC_CTYPE=fi_FI.UTF-8
LD_LIBRARY_PATH (unset)
LOGDIR (unset)
PATH=/home/niko/bin:/home/niko/bin:/home/niko/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/sbin:/usr/sbin:/sbin:/usr/sbin
PERL_BADLANG (unset)
SHELL=/bin/zsh
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[perl #122322] OOK hack example in perlguts is outdated with COW
by Niko Tyni