[perl #71952] crash when looking for a nonexistent destructor

# New Ticket Created by  Niko Tyni 
# Please include the string:  [perl #71952]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=71952 >


This is a bug report for perl from Niko Tyni <nty...@debian.org>,
generated with the help of perlbug 1.39 running under perl 5.10.1.


-----------------------------------------------------------------
The optimization of empty DESTROY methods introduced in commit
fbb3ee5af3d4 causes a null pointer dereference when a destructor is
declared but not defined.

% perl -e 'sub M::DESTROY; bless {}, "M"'
zsh: segmentation fault (core dumped) 

This is seen in the real world with AutoLoader / AutoSplit, where
the crash prevents autoloading a DESTROY method.

 http://bugs.debian.org/564074

Blead backtrace:

Core was generated by `./miniperl -e sub M::DESTROY; bless {}, "M"'.
Program terminated with signal 11, Segmentation fault.
#0  0x000000000054f83a in Perl_sv_clear (my_perl=0x2207010, sv=0x220ae28) at sv.c:5661
5661                || CvSTART(destructor)->op_next->op_type != OP_LEAVESUB))
(gdb) bt
#0  0x000000000054f83a in Perl_sv_clear (my_perl=0x2207010, sv=0x220ae28) at sv.c:5661
#1  0x0000000000551b49 in Perl_sv_free2 (my_perl=0x2207010, sv=0x220ae28) at sv.c:5936
#2  0x000000000054f6a6 in Perl_sv_clear (my_perl=0x2207010, sv=0x220af78) at sv.c:5638
#3  0x0000000000551b49 in Perl_sv_free2 (my_perl=0x2207010, sv=0x220af78) at sv.c:5936
#4  0x00000000005cab0b in Perl_free_tmps (my_perl=0x2207010) at scope.c:167
#5  0x0000000000709457 in perl_run (my_perl=0x2207010) at perl.c:2234
#6  0x00000000006d9921 in main (argc=3, argv=0x7fff5ac22a48, env=0x7fff5ac22a68) at miniperlmain.c:117

Proposed patch attached.
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=medium
---
Site configuration information for perl 5.10.1:

Configured by Debian Project at Sat Nov 21 19:18:01 UTC 2009.

Summary of my perl5 (revision 5 version 10 subversion 1) configuration:
   
  Platform:
    osname=linux, osvers=2.6.31-1-amd64, archname=x86_64-linux-gnu-thread-multi
    uname='linux madeleine 2.6.31-1-amd64 #1 smp mon nov 16 04:44:38 utc 2009 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/5.10.1 -Dsitearch=/usr/local/lib/perl/5.10.1 -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.5.10.1 -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 -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='4.3.4', 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 /usr/lib /lib64 /usr/lib64
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=/lib/libc-2.10.1.so, so=so, useshrplib=true, libperl=libperl.so.5.10.1
    gnulibc_version='2.10.1'
  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:
    

---
@INC for perl 5.10.1:
    /etc/perl
    /usr/local/lib/perl/5.10.1
    /usr/local/share/perl/5.10.1
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.10
    /usr/share/perl/5.10
    /usr/local/lib/site_perl
    .

---
Environment for perl 5.10.1:
    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:/home/niko/bin:/home/niko/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/sbin:/usr/sbin:/sbin:/usr/sbin
    PERL_BADLANG (unset)
    SHELL=/bin/zsh

>From 16026715863b1a3a6e99df6686834c9238922539 Mon Sep 17 00:00:00 2001
From: Niko Tyni <nty...@debian.org>
Date: Fri, 8 Jan 2010 21:21:57 +0200
Subject: [PATCH] Fix a NULL pointer dereference when looking for a DESTROY method

The empty DESTROY method optimization introduced by commit
fbb3ee5af3d would crash the interpreter if a DESTROY method
was declared but not actually defined.

This is seen in the real world with AutoLoader / AutoSplit,
where the crash defeats autoloading a DESTROY method.
---
 sv.c          |    3 ++-
 t/op/method.t |   11 ++++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/sv.c b/sv.c
index fb82caf..ed4be5f 100644
--- a/sv.c
+++ b/sv.c
@@ -5658,7 +5658,8 @@ Perl_sv_clear(pTHX_ register SV *const sv)
 			&& !CvCONST(destructor)
 			/* Don't bother calling an empty destructor */
 			&& (CvISXSUB(destructor)
-			|| CvSTART(destructor)->op_next->op_type != OP_LEAVESUB))
+			|| (CvSTART(destructor)
+			    && (CvSTART(destructor)->op_next->op_type != OP_LEAVESUB))))
 		{
 		    SV* const tmpref = newRV(sv);
 	            SvREADONLY_on(tmpref);   /* DESTROY() could be naughty */
diff --git a/t/op/method.t b/t/op/method.t
index afa8cfb..d2914c4 100644
--- a/t/op/method.t
+++ b/t/op/method.t
@@ -10,7 +10,7 @@ BEGIN {
     require "test.pl";
 }
 
-print "1..78\n";
+print "1..79\n";
 
 @A::ISA = 'B';
 @B::ISA = 'C';
@@ -292,3 +292,12 @@ EOT
 	"check if UNIVERSAL::AUTOLOAD works",
     );
 }
+{
+    fresh_perl_is(<<'EOT',
+sub M::DESTROY; bless {}, "M" ; print "survived\n";
+EOT
+    "survived",
+    {},
+	"no crash with a declared but missing DESTROY method"
+    );
+}
-- 
1.6.6