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[perl #128165] segfault calling method from eval in package DB(regression)

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Date:
May 17, 2016 04:33
Subject:
[perl #128165] segfault calling method from eval in package DB(regression)
Message ID:
rt-4.0.18-13232-1463459587-510.128165-75-0@perl.org
# New Ticket Created by   
# Please include the string:  [perl #128165]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=128165 >



This is a bug report for perl from jim.avera@gmail.com,
generated with the help of perlbug 1.40 running under perl 5.22.1.

-----------------------------------------------------------------
Under some circumstances a string eval in package DB segfaults
if the eval'd code calls a method on an object given by a 
top-level lexical in the caller's package.

This has been distilled from a debugging package I've used for years which
lets you say things like
  print svis('He\'s dead, Jim; The evidence is ${ \( $obj->method ) }.\n');
and the message string is "interpolated", internally using package DB to
access the caller's variables; unlike regular double-quotish interpolation,
if a non-scalar result would be interpolated then Data::Dumper is called 
and the result is substituted instead.

But nevermind that, the below demo simply eval's a constant string.

-> The segfault seems to be "caused" because the call stack contains a
closure which references the same top-level lexical variable.
If that unrelated reference is removed, the segfault does not happen.

-> This is a regression. It started happening when I upgraded Ubuntu and
got Perl v5.22.1.  v5.20.3 (the only other version I have) does not segfault.

#!/usr/bin/perl
use strict; use warnings;

package DB;
sub do_eval { my $str = shift; return eval $str }

package MyClass;
sub new  { return bless {}, 'MyClass' }
sub meth { return "fake-meth-result" }

package main;

my $obj = MyClass->new;

sub get_closure() {
  return sub {

    # -> Comment out the following line and the segfault does not happen
    my $other_reference = \$obj;

    my $x = DB::do_eval('$obj->meth');
    warn "GOT x=$x\n";
  };
}

my $code = get_closure();
$code->();

-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.22.1:

Configured by Debian Project at Sun Mar 13 11:54:18 UTC 2016.

Summary of my perl5 (revision 5 version 22 subversion 1) configuration:
   
  Platform:
    osname=linux, osvers=3.16.0, archname=x86_64-linux-gnu-thread-multi
    uname='linux localhost 3.16.0 #1 smp debian 3.16.0 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dcc=x86_64-linux-gnu-gcc -Dcpp=x86_64-linux-gnu-cpp -Dld=x86_64-linux-gnu-gcc -Dccflags=-DDEBIAN -Wdate-time -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Dldflags= -Wl,-Bsymbolic-functions -Wl,-z,relro -Dlddlflags=-shared -Wl,-Bsymbolic-functions -Wl,-z,relro -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.22 -Darchlib=/usr/lib/x86_64-linux-gnu/perl/5.22 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/x86_64-linux-gnu/perl5/5.22 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.22.1 -Dsitearch=/usr/local/lib/x86_64-linux-gnu/perl/5.22.1 -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 -
 Doptimiz
 e=-O2 -dEs -Duseshrplib -Dlibperl=libperl.so.5.22.1'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='x86_64-linux-gnu-gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv -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 -fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='5.3.1 20160311', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678, doublekind=3
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16, longdblkind=3
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='x86_64-linux-gnu-gcc', ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/5/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=libc-2.21.so, so=so, useshrplib=true, libperl=libperl.so.5.22
    gnulibc_version='2.21'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib -fstack-protector-strong'

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 under /usr/lib
    DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or perllocal.pod for perl or vendor
    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/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/deprecate-with-apt - http://bugs.debian.org/747628 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 5.22.1-9 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/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:debian/regen-skip - Skip a regeneration check in unrelated git repositories
    DEBPKG:debian/makemaker-pasthru - http://bugs.debian.org/758471 Pass LD settings through to subdirectories
    DEBPKG:fixes/pod_man_reproducible_date - http://bugs.debian.org/759405 Support POD_MAN_DATE in Pod::Man for the left-hand footer
    DEBPKG:debian/locale-robustness - http://bugs.debian.org/782068 [perl #124310] Make t/run/locale.t survive missing locales masked by LC_ALL
    DEBPKG:fixes/podman-utc - http://bugs.debian.org/780259 Make the embedded date from Pod::Man reproducible
    DEBPKG:fixes/podman-utc-docs - http://bugs.debian.org/780259 Documentation and test suite updates for UTC fix
    DEBPKG:fixes/podman-empty-date - http://bugs.debian.org/780259 Support an empty POD_MAN_DATE environment variable
    DEBPKG:fixes/podman-pipe - http://bugs.debian.org/777405 Better errors for man pages from standard input
    DEBPKG:debian/pod2man-customized - Update porting/customized.dat for pod2man modifications
    DEBPKG:debian/makemaker-manext - http://bugs.debian.org/247370 Make EU::MakeMaker honour MANnEXT settings in generated manpage headers
    DEBPKG:debian/makemaker_customized - Update t/porting/customized.dat for files patched in Debian
    DEBPKG:debian/do-not-record-build-date - [6baa8db] http://bugs.debian.org/774422 [perl #125830] Allow overriding the compile time in "perl -V" output
    DEBPKG:fixes/podman-source-date-epoch - http://bugs.debian.org/801621 Make Pod::Man honor the SOURCE_DATE_EPOCH environment variable
    DEBPKG:fixes/podman-source-date-epoch-cleanups - http://bugs.debian.org/801621 Coding style and documentation for SOURCE_EPOCH_DATE
    DEBPKG:fixes/podman-source-date-epoch-testfix - http://bugs.debian.org/807086 Guard for building with SOURCE_DATE_EPOCH or POD_MAN_DATE set
    DEBPKG:debian/devel-ppport-reproducibility - http://bugs.debian.org/801523 Sort the list of XS code files when generating RealPPPort.xs
    DEBPKG:fixes/encode-unicode-bom - http://bugs.debian.org/798727 [rt.cpan.org #107043] Address https://rt.cpan.org/Public/Bug/Display.html?id=107043
    DEBPKG:debian/encode-unicode-bom-doc - http://bugs.debian.org/798727 Document Debian backport of Encode::Unicode fix
    DEBPKG:debian/kfreebsd-softupdates - http://bugs.debian.org/796798 Work around Debian Bug#796798
    DEBPKG:fixes/autodie-scope - http://bugs.debian.org/798096 Fix a scoping issue with "no autodie" and the "system" sub
    DEBPKG:debian/debugperl-compat-fix - [perl #127212] http://bugs.debian.org/810326 Disable PERL_TRACK_MEMPOOL for debugging builds
    DEBPKG:fixes/CVE-2015-8607_file_spec_taint_fix - http://bugs.debian.org/810719 [perl #126862] ensure File::Spec::canonpath() preserves taint
    DEBPKG:fixes/mkstemp-umask - http://bugs.debian.org/810924 [perl #127322] [e57270b] Fix umask for mkstemp(3) calls
    DEBPKG:fixes/crosscompile-no-targethost - [perl #127234] Fix the Configure escape with usecrosscompile but no targethost
    DEBPKG:fixes/podlators-no-encode - [rt.cpan.org #111156] Degrade gracefully if utf8 is requested but Encode is not available
    DEBPKG:debian/cross-time-hires - [rt.cpan.org #111391] Add an environment variable to skip running configuration probes
    DEBPKG:fixes/encode-unicode-pod - Unicode.pm: Fix POD error
    DEBPKG:fixes/memoize-pod - [rt.cpan.org #89441] Fix POD errors in Memoize
    DEBPKG:fixes/ok-pod - Added encoding for pod.
    DEBPKG:fixes/CVE-2016-2381_duplicate_env - remove duplicate environment variables from environ

---
@INC for perl 5.22.1:
    /home/jima/perl5/lib/perl5/5.22.1/x86_64-linux-gnu-thread-multi
    /home/jima/perl5/lib/perl5/5.22.1
    /home/jima/perl5/lib/perl5/x86_64-linux-gnu-thread-multi
    /home/jima/perl5/lib/perl5
    /home/jima/lib/perl
    /etc/perl
    /usr/local/lib/x86_64-linux-gnu/perl/5.22.1
    /usr/local/share/perl/5.22.1
    /usr/lib/x86_64-linux-gnu/perl5/5.22
    /usr/share/perl5
    /usr/lib/x86_64-linux-gnu/perl/5.22
    /usr/share/perl/5.22
    /usr/local/lib/site_perl
    /usr/lib/x86_64-linux-gnu/perl-base
    .

---
Environment for perl 5.22.1:
    HOME=/home/jima
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/jima/perl5/perlbrew/bin:/home/jima/perl5/bin:/home/jima/bin:/home/jima/jima_tools/x86_64/bin:/home/jima/jima_tools/bin:/opt/Adobe/Reader9/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/bin/X11:/usr/local/games:/usr/games:/usr/lib/jvm/java-8-oracle/bin:/usr/lib/jvm/java-8-oracle/db/bin:/usr/lib/jvm/java-8-oracle/jre/bin:.
    PERL5LIB=/home/jima/perl5/lib/perl5:/home/jima/lib/perl
    PERLBREW_BASHRC_VERSION=0.75
    PERLBREW_HOME=/home/jima/.perlbrew
    PERLBREW_PATH=/home/jima/perl5/perlbrew/bin
    PERLBREW_ROOT=/home/jima/perl5/perlbrew
    PERLBREW_VERSION=0.75
    PERL_BADLANG (unset)
    PERL_LOCAL_LIB_ROOT=/home/jima/perl5
    PERL_MB_OPT=--install_base "/home/jima/perl5"
    PERL_MM_OPT=INSTALL_BASE=/home/jima/perl5
    SHELL=/bin/bash


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