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[perl #54566] assertion failure fiddling with @ISA

 

 

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perlbug-followup at perl

May 20, 2008, 11:54 PM

Post #1 of 3 (93 views)
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[perl #54566] assertion failure fiddling with @ISA

# New Ticket Created by Niko Tyni
# Please include the string: [perl #54566]
# in the subject line of all future correspondence about this issue.
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=54566 >



This is a bug report for perl from Niko Tyni <ntyni[at]debian.org>,
generated with the help of perlbug 1.36 running under perl 5.10.0.


-----------------------------------------------------------------
This one-liner, reduced from code in HTML::Mason::Request, causes an
assertion failure on blead[at]33852:

% ./miniperl -e '@ISA=q/a/; $#ISA; $ISA[0]=q/b/'
miniperl: mg.c:1587: Perl_magic_setisa: Assertion `((((_gv)->sv_flags & (0x00004000|0x00008000)) == 0x00008000) && (((svtype)((_gv)->sv_flags & 0xff)) == SVt_PVGV || ((svtype)((_gv)->sv_flags & 0xff)) == SVt_PVLV))' failed.
zsh: abort (core dumped) ./miniperl -e '@ISA=q/a/; $#ISA; $ISA[0]=q/b/'

#0 0x00002b6aba3ac165 in raise () from /lib/libc.so.6
#1 0x00002b6aba3ad610 in abort () from /lib/libc.so.6
#2 0x00002b6aba3a560f in __assert_fail () from /lib/libc.so.6
#3 0x00000000004c7ae7 in Perl_magic_setisa (my_perl=0x985010, sv=0x988e78, mg=0x9b0988) at mg.c:1583
#4 0x00000000004c05f5 in Perl_mg_set (my_perl=0x985010, sv=0x988e78) at mg.c:291
#5 0x000000000050434c in Perl_pp_sassign (my_perl=0x985010) at pp_hot.c:196
#6 0x00000000004ad840 in Perl_runops_debug (my_perl=0x985010) at dump.c:1984
#7 0x00000000004f7072 in S_run_body (my_perl=0x985010, oldscope=1) at perl.c:2392
#8 0x00000000004f63a4 in perl_run (my_perl=0x985010) at perl.c:2312
#9 0x00000000006b1712 in main (argc=3, argv=0x7ffff121fdf8, env=0x7ffff121fe18) at miniperlmain.c:113

As seen in <http://bugs.debian.org/480480>, this segfaults on 5.10.0
in the subsequent call to Perl_mro_isa_changed_in() as 'stash' ends up NULL.

The segfault is gone with change 33684, but the assertion failure remains
with -DDEBUGGING, indicating there's another bug in there.
-----------------------------------------------------------------
---
Flags:
category=core
severity=medium
---
Site configuration information for perl 5.10.0:

Configured by Debian Project at Tue May 20 20:09:17 UTC 2008.

Summary of my perl5 (revision 5 version 10 subversion 0) configuration:
Platform:
osname=linux, osvers=2.6.18-6-xen-amd64, archname=x86_64-linux-gnu-thread-multi
uname='linux sid 2.6.18-6-xen-amd64 #1 smp thu may 8 08:34:37 utc 2008 x86_64 gnulinux '
config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.10 -Darchlib=/usr/lib/perl/5.10 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.10.0 -Dsitearch=/usr/local/lib/perl/5.10.0 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dlibperl=libperl.so.5.10.0 -Dd_dosuid -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 -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 -I/usr/local/include'
ccversion='', gccversion='4.2.3 (Debian 4.2.3-5)', 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 =' -L/usr/local/lib'
libpth=/usr/local/lib /lib /usr/lib /lib64 /usr/lib64
libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
perllibs=-ldl -lm -lpthread -lc -lcrypt
libc=/lib/libc-2.7.so, so=so, useshrplib=true, libperl=libperl.so.5.10.0
gnulibc_version='2.7'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib'

Locally applied patches:


---
@INC for perl 5.10.0:
/etc/perl
/usr/local/lib/perl/5.10.0
/usr/local/share/perl/5.10.0
/usr/lib/perl5
/usr/share/perl5
/usr/lib/perl/5.10
/usr/share/perl/5.10
/usr/local/lib/site_perl
.

---
Environment for perl 5.10.0:
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:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games:/sbin:/usr/sbin
PERL_BADLANG (unset)
SHELL=/bin/zsh


rgarciasuarez at gmail

May 21, 2008, 5:42 AM

Post #2 of 3 (84 views)
Permalink
Re: [perl #54566] assertion failure fiddling with @ISA [In reply to]

2008/5/21 via RT Niko Tyni <perlbug-followup[at]perl.org>:
> This one-liner, reduced from code in HTML::Mason::Request, causes an
> assertion failure on blead[at]33852:
>
> % ./miniperl -e '@ISA=q/a/; $#ISA; $ISA[0]=q/b/'
> miniperl: mg.c:1587: Perl_magic_setisa: Assertion `((((_gv)->sv_flags & (0x00004000|0x00008000)) == 0x00008000) && (((svtype)((_gv)->sv_flags & 0xff)) == SVt_PVGV || ((svtype)((_gv)->sv_flags & 0xff)) == SVt_PVLV))' failed.
> zsh: abort (core dumped) ./miniperl -e '@ISA=q/a/; $#ISA; $ISA[0]=q/b/'
>

Looks like the original author of the code overlooked the possibility
for @ISA to have several kinds of magic.

Here's a patch :

--- mg.c.orig 2008-05-12 18:29:57.000000000 +0200
+++ mg.c 2008-05-21 14:23:45.000000000 +0200
@@ -1583,7 +1583,7 @@ Perl_magic_setisa(pTHX_ SV *sv, MAGIC *m
stash = GvSTASH(
SvTYPE(mg->mg_obj) == SVt_PVGV
? (GV*)mg->mg_obj
- : (GV*)SvMAGIC(mg->mg_obj)->mg_obj
+ : (GV*)mg_find(mg->mg_obj, PERL_MAGIC_isa)->mg_obj
);

if (stash)
@@ -1609,7 +1609,7 @@ Perl_magic_clearisa(pTHX_ SV *sv, MAGIC
stash = GvSTASH(
SvTYPE(mg->mg_obj) == SVt_PVGV
? (GV*)mg->mg_obj
- : (GV*)SvMAGIC(mg->mg_obj)->mg_obj
+ : (GV*)mg_find(mg->mg_obj, PERL_MAGIC_isa)->mg_obj
);

if (stash)


h.m.brand at xs4all

May 21, 2008, 6:00 AM

Post #3 of 3 (85 views)
Permalink
Re: [perl #54566] assertion failure fiddling with @ISA [In reply to]

On Wed, 21 May 2008 14:42:48 +0200, "Rafael Garcia-Suarez"
<rgarciasuarez[at]gmail.com> wrote:

> 2008/5/21 via RT Niko Tyni <perlbug-followup[at]perl.org>:
> > This one-liner, reduced from code in HTML::Mason::Request, causes an
> > assertion failure on blead[at]33852:
> >
> > % ./miniperl -e '@ISA=q/a/; $#ISA; $ISA[0]=q/b/'
> > miniperl: mg.c:1587: Perl_magic_setisa: Assertion `((((_gv)->sv_flags & (0x00004000|0x00008000)) == 0x00008000) && (((svtype)((_gv)->sv_flags & 0xff)) == SVt_PVGV || ((svtype)((_gv)->sv_flags & 0xff)) == SVt_PVLV))' failed.
> > zsh: abort (core dumped) ./miniperl -e '@ISA=q/a/; $#ISA; $ISA[0]=q/b/'
> >
>
> Looks like the original author of the code overlooked the possibility
> for @ISA to have several kinds of magic.
>
> Here's a patch :

Change 33898 submitted.

> --- mg.c.orig 2008-05-12 18:29:57.000000000 +0200
> +++ mg.c 2008-05-21 14:23:45.000000000 +0200
> @@ -1583,7 +1583,7 @@ Perl_magic_setisa(pTHX_ SV *sv, MAGIC *m
> stash = GvSTASH(
> SvTYPE(mg->mg_obj) == SVt_PVGV
> ? (GV*)mg->mg_obj
> - : (GV*)SvMAGIC(mg->mg_obj)->mg_obj
> + : (GV*)mg_find(mg->mg_obj, PERL_MAGIC_isa)->mg_obj
> );
>
> if (stash)
> @@ -1609,7 +1609,7 @@ Perl_magic_clearisa(pTHX_ SV *sv, MAGIC
> stash = GvSTASH(
> SvTYPE(mg->mg_obj) == SVt_PVGV
> ? (GV*)mg->mg_obj
> - : (GV*)SvMAGIC(mg->mg_obj)->mg_obj
> + : (GV*)mg_find(mg->mg_obj, PERL_MAGIC_isa)->mg_obj
> );
>
> if (stash)

--
H.Merijn Brand Amsterdam Perl Mongers (http://amsterdam.pm.org/)
using & porting perl 5.6.2, 5.8.x, 5.10.x on HP-UX 10.20, 11.00, 11.11,
& 11.23, SuSE 10.1 & 10.2, AIX 5.2, and Cygwin. http://qa.perl.org
http://mirrors.develooper.com/hpux/ http://www.test-smoke.org
http://www.goldmark.org/jeff/stupid-disclaimers/

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