[FATAL 5.005_03 & 5.005_60] Segfault in Perl_pad_free

[p5pRT]

Migrated from rt.perl.org#1241 (status was 'resolved')

Searchable as RT1241$

[p5pRT]

From @schwern

$ perl -cw Schema.pm
Global symbol "%COLUMNS" requires explicit package name at Schema.pm line 203.
syntax error at Schema.pm line 233, near "no strict ="
Segmentation fault

Simliar error with 5.005_60...

$ /usr/local/perl5.005_60/bin/perl -cw Schema.pm
Global symbol "%COLUMNS" requires explicit package name at Schema.pm line 203.
syntax error at Schema.pm line 233, near "no strict ="
defined(%hash) is deprecated at Schema.pm line 235.
(Maybe you should just omit the defined()?)
Segmentation fault

No core file was generated. Fortunately, I happen to have 5.005_60
compiled with debugging flags​:

Program received signal SIGSEGV, Segmentation fault.
0x807fc88 in Perl_pad_free (po=6) at op.c​:496
496 SvPADTMP_off(PL_curpad[po]);
(gdb) bt
#0 0x807fc88 in Perl_pad_free (po=6) at op.c​:496
#1 0x8080068 in S_op_clear (o=0x823e848) at op.c​:723
#2 0x807fe70 in Perl_op_free (o=0x823e848) at op.c​:650
#3 0x807fe15 in Perl_op_free (o=0x823e6c8) at op.c​:638
#4 0x807fe15 in Perl_op_free (o=0x823de88) at op.c​:638
#5 0x807fe15 in Perl_op_free (o=0x8240488) at op.c​:638
#6 0x807fe15 in Perl_op_free (o=0x823fbc8) at op.c​:638
#7 0x807fe15 in Perl_op_free (o=0x823fa48) at op.c​:638
#8 0x807fe15 in Perl_op_free (o=0x823fb48) at op.c​:638
#9 0x807fe15 in Perl_op_free (o=0x8243ec8) at op.c​:638
#10 0x807fe15 in Perl_op_free (o=0x8243f08) at op.c​:638
#11 0x807fe15 in Perl_op_free (o=0x8243988) at op.c​:638
#12 0x8088abf in Perl_newSUB (floor=84, o=0x823e0c8, proto=0x0,
  block=0x8243988) at op.c​:4010
#13 0x807cb8d in Perl_yyparse () at perly.y​:293
#14 0x805bcbb in S_parse_body (args=0xbffffb74) at perl.c​:951
#15 0x80d517e in Perl_vdefault_protect (excpt=0xbffffb84,
  body=0x805b330 <S_parse_body>, args=0xbffffb54) at scope.c​:44
#16 0x80d50b0 in Perl_default_protect (excpt=0xbffffb84,
  body=0x805b330 <S_parse_body>) at scope.c​:25
#17 0x805b23f in perl_parse (my_perl=0x8128408, xsinit=0x8059758 <xs_init>,
  argc=3, argv=0xbffffc34, env=0x0) at perl.c​:630
#18 0x80596f9 in main (argc=3, argv=0xbffffc34, env=0xbffffc44)
  at perlmain.c​:51

Some other useful information​:
(gdb) print **PL_curpad
$15 = {sv_any = 0x0, sv_refcnt = 2147483170, sv_flags = 8388608}
That ref count is a wee high, no?

I'm sorry, I can't provide a copy of the module which caused the
problem, its kinda confidential. I'll try to break it down into a
simple case, but somehow I doubt I can do that.

Summary of my perl5 (revision 5.0 version 5 subversion 60) configuration​:
  Platform​:
  osname=linux, osvers=2.2.10, archname=i686-linux
  uname='linux athens 2.2.10 #3 smp mon aug 2 16​:48​:09 edt 1999 i686 unknown '
  config_args=''
  hint=previous, useposix=true, d_sigaction=define
  usethreads=undef useperlio=undef d_sfio=undef
  use64bits=undef usemultiplicity=undef
  Compiler​:
  cc='gcc', optimize='-g', gccversion=2.95.1 19990809 (prerelease)
  cppflags='-Dbool=char -DHAS_BOOL -DDEBUGGING -DDEBUGGING_MSTATS -DDEBUGGING_OPS'
  ccflags ='-Dbool=char -DHAS_BOOL -DDEBUGGING -DDEBUGGING_MSTATS -DDEBUGGING_OPS'
  stdchar='char', d_stdstdio=define, usevfork=false
  intsize=4, longsize=4, ptrsize=4, doublesize=8
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
  alignbytes=4, usemymalloc=y, prototype=define
  Linker and Libraries​:
  ld='cc', ldflags =' -L/usr/local/lib'
  libpth=/usr/local/lib /lib /usr/lib
  libs=-lnsl -lndbm -lgdbm -ldbm -ldb -ldl -lm -lrt -lc -lposix -lcrypt
  libc=/lib/libc-2.1.2.so, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
  cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'

Characteristics of this binary (from libperl)​:
  Compile-time options​: DEBUGGING
  Built under linux
  Compiled at Aug 17 1999 18​:05​:39
  %ENV​:
  PERL5LIB="/home/schwern/lib/perl5/site_perl/5.005"
  @​INC​:
  /home/schwern/lib/perl5/site_perl/5.005/i686-linux
  /home/schwern/lib/perl5/site_perl/5.005
  /usr/local/perl5.005_60/lib/i686-linux
  /usr/local/perl5.005_60/lib
  /usr/local/perl5.005_60/lib/site_perl/5.00560/i686-linux
  /usr/local/perl5.005_60/lib/site_perl
  .

--

Michael G Schwern schwern@​pobox.com
  http​://www.pobox.com/~schwern
  /(?​:(?​:(1)[.-]?)?\(?(\d{3})\)?[.-]?)?(\d{3})[.-]?(\d{4})(x\d+)?/i

[p5pRT]

From @schwern

On Fri, Aug 20, 1999 at 12​:54​:00PM -0400, Spider Boardman wrote​:

I don't know what gdb means by '$15'. What would be the result of

\(gdb\) print PL\_curpad\[6\]\[0\]

The high sv_refcnt you saw is normal for things marked readonly
at compile time, since it helps to keep the constants around.

(gdb) print PL_curpad[6][0]
Cannot access memory at address 0x55555555.

Okay, I can see this is going to be a painful debugging process, so
I'm just going to give you guys a copy of the code causing the error.
However, I'm about to leave for TPC in like, 5 minutes. I'll send the
code along later, sorry to be a tease!

--

Michael G Schwern schwern@​pobox.com
  http​://www.pobox.com/~schwern
  /(?​:(?​:(1)[.-]?)?\(?(\d{3})\)?[.-]?)?(\d{3})[.-]?(\d{4})(x\d+)?/i