Debugger corrupts symbol table munging

[p5pRT]

Migrated from rt.perl.org#48332 (status was 'resolved')

Searchable as RT48332$

[p5pRT]

From mjcarman@mchsi.com

Created by mjcarman@mchsi.com

This is a bug report for perl from mjcarman@​mchsi.com,
generated with the help of perlbug 1.35 running under perl v5.8.8.

-----------------------------------------------------------------

Given the following script​:

  use strict;
  use warnings;
 
  sub foo { print "1\n" }
 
  {
  no warnings 'redefine';
  *old_foo = \&foo;
  *foo = sub { print "2\n" }
  }
 
  old_foo();
  foo();
 
  __END__

Run normally, this works as expected. (i.e. it prints 1, 2) When run under the debugger,
*old_foo incorrectly points to the new foo(). (i.e. it prints 2, 2)

In the particular case where I noticed this bug the new foo() was a wrapper which called
old_foo(). This created an infinite recursion which the debugger eventually bailed out
of with the message "100 levels deep in subroutine calls!"

Perl Info

Flags:
    category=utilities
    severity=low

Site configuration information for perl v5.8.8:

Configured by SYSTEM at Tue Jul 31 19:34:29 2007.

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
  Platform:
    osname=MSWin32, osvers=5.00, archname=MSWin32-x86-multi-thread
    uname=''
    config_args='undef'
    hint=recommended, useposix=true, d_sigaction=undef
    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='gcc', ccflags ='-DNDEBUG -DWIN32 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT -DNO_HASH_SEED -DUSE_SITECUSTOMIZE -DPRIVLIB_LAST_IN_INC -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DUSE_PERLIO -DPERL_MSVCRT_READFIX -DHASATTRIBUTE -fno-strict-aliasing',
    optimize='-O2',
    cppflags='-DWIN32'
    ccversion='', gccversion='3.4.2 (mingw-special)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=8
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='__int64', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='g++', ldflags ='-L"C:\Perl\lib\CORE"'
    libpth=\lib
    libs=-lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 -lmsvcrt
    perllibs=-lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 -lmsvcrt
    libc=msvcrt.lib, so=dll, useshrplib=true, libperl=perl58.lib
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags='-mdll -L"C:\Perl\lib\CORE"'

Locally applied patches:
    ACTIVEPERL_LOCAL_PATCHES_ENTRY
    Iin_load_module moved for compatibility with build 806
    Avoid signal flag SA_RESTART for older versions of HP-UX
    PerlEx support in CGI::Carp
    Less verbose ExtUtils::Install and Pod::Find
    Patch for CAN-2005-0448 from Debian with modifications
    Rearrange @INC so that 'site' is searched before 'perl'
    Partly reverted 24733 to preserve binary compatibility
    MAINT31223 plus additional changes
    31490 Problem bootstraping Win32CORE
    31324 Fix DynaLoader::dl_findfile() to locate .so files again
    31214 Win32::GetLastError fails when first called
    31211 Restore Windows NT support
    31188 Problem killing a pseudo-forked child on Win32
    29732 ANSIfy the PATH environment variable on Windows
    27527,29868 win32_async_check() can loop indefinitely
    26970 Make Passive mode the default for Net::FTP
    26379 Fix alarm() for Windows 2003
    24699 ICMP_UNREACHABLE handling in Net::Ping


@INC for perl v5.8.8:
    C:/Perl/site/lib
    C:/Perl/lib
    .


Environment for perl v5.8.8:
    HOME (unset)
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=C:\Program Files\Microsoft IntelliType Pro\;C:\Perl\bin;C:\WINDOWS;C:\WINDOWS\System32;C:\WINDOWS\System32\wbem;C:\Lotus\Notes\Data;C:\Lotus\Notes;C:\Program Files\Rational\ClearCase\bin;C:\Program Files\Rational\common;C:\Program Files\QuickTime\QTSystem\;C:\PROGRA~1\ATT\Graphviz\bin;C:\Tools;C:\Perl\site\bin;C:\MinGW\bin;Z:\FlexIO\Tools
    PERL_BADLANG (unset)
    SHELL (unset)

[p5pRT]

From @iabyn

I can't reproduce this in 5.8.8, but its present in 5.9.4, 5.10.0 and bleed​:

[davem@​pigeon bleed]$ ./perl -d /tmp/p

Loading DB routines from perl5db.pl version 1.33
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main​::(/tmp/p​:9)​: no warnings 'redefine';
  DB<1> c
2
2
Debugged program terminated. Use q to quit or R to restart,
  use o inhibit_exit to avoid stopping after program termination,
  h q, h R or h o to get additional info.
  DB<1>

[p5pRT]

@iabyn - Status changed from 'new' to 'open'

[p5pRT]

From @cpansprout

Fixed by be1cc45.

[p5pRT]

@cpansprout - Status changed from 'open' to 'resolved'

[p5pRT]

From @salva

Created by @salva

If some function &A​::foo is exported to package B becomming &B​::foo, then, assigning a new CODE ref to *A​::foo also unexpectedly changes B​::foo.

The funny thing is that getting a reference to B​::foo returns a reference to the former function!

Debugger session follows​:

  DB<1> sub foo { print "former foo\n" }

  DB<2> *M​::foo = \&foo;

  DB<3> *foo = sub { print "reformed foo\n" }

  DB<4> x M​::foo
reformed foo
0  1
  DB<5> x (\&M​::foo)->()
former foo
0  1

Perl Info

Flags:
    category=core
    severity=high

Site configuration information for perl 5.12.3:

Configured by Debian Project at Thu May  5 10:00:04 UTC 2011.

Summary of my perl5 (revision 5 version 12 subversion 3) configuration:
   
  Platform:
    osname=linux, osvers=2.6.24-28-server, archname=x86_64-linux-gnu-thread-multi
    uname='linux allspice 2.6.24-28-server #1 smp wed aug 18 21:17:51 utc 2010 x86_64 x86_64 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.12 -Darchlib=/usr/lib/perl/5.12 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.12.3 -Dsitearch=/usr/local/lib/perl/5.12.3 -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 -DDEBUGGING=-g -Doptimize=-O2 -Dplibpth=/lib/x86_64-linux-gnu /usr/lib/x86_64-linux-gnu -Duseshrplib -Dlibperl=libperl.so.5.12.3 -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 -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.6.1 20110503 (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 =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib/x86_64-linux-gnu /usr/lib/x86_64-linux-gnu /lib /usr/lib /lib64 /usr/lib64
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=, so=so, useshrplib=true, libperl=libperl.so.5.12.3
    gnulibc_version='2.13'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib -fstack-protector'

Locally applied patches:
    DEBPKG:debian/arm_thread_stress_timeout - http://bugs.debian.org/501970 Raise the timeout of ext/threads/shared/t/stress.t to accommodate slower build hosts
    DEBPKG:debian/cpan_config_path - Set location of CPAN::Config to /etc/perl as /usr may not be writable.
    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/extutils_hacks - Various debian-specific ExtUtils changes
    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/m68k_thread_stress - http://bugs.debian.org/495826 Disable some threads tests on m68k for now due to missing TLS.
    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 - http://bugs.debian.org/100195 [rt.cpan.org #36038] Document the Net::SMTP 'Port' option
    DEBPKG:fixes/processPL - http://bugs.debian.org/357264 [rt.cpan.org #17224] Always use PERLRUNINST when building perl modules.
    DEBPKG:debian/perlivp - http://bugs.debian.org/510895 Make perlivp skip include directories in /usr/local
    DEBPKG:debian/disable-zlib-bundling - Disable zlib bundling in Compress::Raw::Zlib
    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:fixes/autodie-flock - http://bugs.debian.org/543731 Allow for flock returning EAGAIN instead of EWOULDBLOCK on linux/parisc
    DEBPKG:debian/devel-ppport-ia64-optim - http://bugs.debian.org/548943 Work around an ICE on ia64
    DEBPKG:fixes/cpanplus-without-home - http://bugs.debian.org/577011 [rt.cpan.org #52988] Fix CPANPLUS test failures when HOME doesn't exist
    DEBPKG:debian/arm_optim - http://bugs.debian.org/580334 Downgrade the optimization of sv.c on arm due to a gcc-4.4 bug
    DEBPKG:debian/deprecate-with-apt - http://bugs.debian.org/580034 Point users to Debian packages of deprecated core modules
    DEBPKG:fixes/hurd-ccflags - http://bugs.debian.org/587901 Make hints/gnu.sh append to $ccflags rather than overriding them
    DEBPKG:debian/squelch-locale-warnings - http://bugs.debian.org/508764 Squelch locale warnings in Debian package maintainer scripts
    DEBPKG:fixes/lc-numeric-docs - http://bugs.debian.org/379329 [perl #78452] [903eb63] LC_NUMERIC documentation fixes
    DEBPKG:fixes/lc-numeric-sprintf - http://bugs.debian.org/601549 [perl #78632] [b3fd614] Fix sprintf not to ignore LC_NUMERIC with constants
    DEBPKG:fixes/concat-stack-corruption - http://bugs.debian.org/596105 [perl #78674] [e3393f5] Fix stack pointer corruption in pp_concat() with 'use encoding'
    DEBPKG:fixes/h2ph-gcc-4.5 - http://bugs.debian.org/599933 [8d66b3f] h2ph fix for gcc 4.5
    DEBPKG:fixes/casing-taint-cve-2011-1487 - http://bugs.debian.org/622817 [perl #87336] fix unwanted taint laundering in lc(), uc() et al.
    DEBPKG:fixes/correct-module-corelist-version - [a0a0e54] Correct the version of Module::CoreList that was released with v5.12.3
    DEBPKG:patchlevel - http://bugs.debian.org/567489 List packaged patches for 5.12.3-6 in patchlevel.h


@INC for perl 5.12.3:
    /etc/perl
    /usr/local/lib/perl/5.12.3
    /usr/local/share/perl/5.12.3
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.12
    /usr/share/perl/5.12
    /usr/local/lib/site_perl
    .


Environment for perl 5.12.3:
    HOME=/home/salva
    LANG=en_US.UTF-8
    LANGUAGE=en_US:en
    LC_MESSAGES=en_US.UTF-8
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/sbin:/sbin:/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

[p5pRT]

From @cpansprout

On Wed Jul 06 06​:27​:52 2011, salva wrote​:

If some function &A​::foo is exported to package B becomming &B​::foo,
then, assigning a new CODE ref to *A​::foo also unexpectedly changes
B​::foo.

The funny thing is that getting a reference to B​::foo returns a
reference to the former function!

Debugger session follows​:

� DB<1> sub foo { print "former foo\n" }

� DB<2> *M​::foo = \&foo;

� DB<3> *foo = sub { print "reformed foo\n" }

� DB<4> x M​::foo
reformed foo
0� 1
� DB<5> x (\&M​::foo)->()
former foo
0� 1

This is the same bug as #48332, which was fixed in 5.14.0.

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

@cpansprout - Status changed from 'open' to 'resolved'

[p5pRT]

From @iabyn

On Wed, Jul 06, 2011 at 06​:27​:53AM -0700, Salvador Fandiño wrote​:

If some function &A​::foo is exported to package B becomming &B​::foo, then, assigning a new CODE ref to *A​::foo also unexpectedly changes B​::foo.

The funny thing is that getting a reference to B​::foo returns a reference to the former function!

Debugger session follows​:

  DB<1> sub foo { print "former foo\n" }

  DB<2> *M​::foo = \&foo;

  DB<3> *foo = sub { print "reformed foo\n" }

  DB<4> x M​::foo
reformed foo
0  1
  DB<5> x (\&M​::foo)->()
former foo
0  1

This appears to have been fixed somewhere between 5.13.4 and 5.13.6

--
"You're so sadly neglected, and often ignored.
A poor second to Belgium, When going abroad."
  -- Monty Python, "Finland"