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[perl #54566] assertion failure fiddling with @ISA

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Niko Tyni
May 21, 2008 04:14
[perl #54566] assertion failure fiddling with @ISA
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# New Ticket Created by  Niko Tyni 
# Please include the string:  [perl #54566]
# in the subject line of all future correspondence about this issue. 
# <URL: >

This is a bug report for perl from Niko Tyni <>,
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@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/
#1  0x00002b6aba3ad610 in abort () from /lib/
#2  0x00002b6aba3a560f in __assert_fail () from /lib/
#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 <>, 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.
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:
    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 -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
    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/, so=so, useshrplib=true,
  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:

Environment for perl 5.10.0:
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PERL_BADLANG (unset)

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