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In-memory read from undefined variable can return junk #7510

Closed p5pRT closed 20 years ago

p5pRT commented 20 years ago

Migrated from rt.perl.org#31692 (status was 'resolved')

Searchable as RT31692$

p5pRT commented 20 years ago

From perl@pythontech.co.uk

This is a bug report for perl from perl@​pythontech.co.uk\, generated with the help of perlbug 1.34 running under perl v5.8.3.

# 13 characters of junk are printed. # I expect nothing to be printed.

$data = "13 characters"; $data = undef;

open(MEM\,'\<'\,\$data) or die "Fail​: $!\n"; while (\) {   print; }

Flags​:   category=core   severity=medium

Site configuration information for perl v5.8.3​:

Configured by bhcompile at Thu Apr 15 13​:08​:28 EDT 2004.

Summary of my perl5 (revision 5.0 version 8 subversion 3) configuration​:   Platform​:   osname=linux\, osvers=2.4.21-4.elsmp\, archname=i386-linux-thread-multi   uname='linux tweety.devel.redhat.com 2.4.21-4.elsmp #1 smp fri oct 3 17​:52​:56 edt 2003 i686 i686 i386 gnulinux '   config_args='-des -Doptimize=-O2 -g -pipe -march=i386 -mcpu=i686 -Dversion=5.8.3 -Dmyhostname=localhost -Dperladmin=root@​localhost -Dcc=gcc -Dcf_by=Red Hat\, Inc. -Dinstallprefix=/usr -Dprefix=/usr -Darchname=i386-linux -Dvendorprefix=/usr -Dsiteprefix=/usr -Duseshrplib -Dusethreads -Duseithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallusrbinperl -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dinc_version_list=5.8.2 5.8.1 5.8.0'   hint=recommended\, useposix=true\, d_sigaction=define   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 ='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBUGGING -fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm'\,   optimize='-O2 -g -pipe -march=i386 -mcpu=i686'\,   cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBUGGING -fno-strict-aliasing -I/usr/local/include -I/usr/include/gdbm'   ccversion=''\, gccversion='3.3.3 20040412 (Red Hat Linux 3.3.3-7)'\, gccosandvers=''   intsize=4\, longsize=4\, ptrsize=4\, doublesize=8\, byteorder=1234   d_longlong=define\, longlongsize=8\, d_longdbl=define\, longdblsize=12   ivtype='long'\, ivsize=4\, nvtype='double'\, nvsize=8\, Off_t='off_t'\, lseeksize=8   alignbytes=4\, prototype=define   Linker and Libraries​:   ld='gcc'\, ldflags =' -L/usr/local/lib'   libpth=/usr/local/lib /lib /usr/lib   libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc   perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc   libc=/lib/libc-2.3.3.so\, so=so\, useshrplib=true\, libperl=libperl.so   gnulibc_version='2.3.3'   Dynamic Linking​:   dlsrc=dl_dlopen.xs\, dlext=so\, d_dlsymun=undef\, ccdlflags='-rdynamic -Wl\,-rpath\,/usr/lib/perl5/5.8.3/i386-linux-thread-multi/CORE'   cccdlflags='-fPIC'\, lddlflags='-shared -L/usr/local/lib'

Locally applied patches​:  

@​INC for perl v5.8.3​:   /usr/lib/perl5/site_perl/jac_perl/5.8.3/i386-linux-thread-multi   /usr/lib/perl5/site_perl/jac_perl/5.8.3   /usr/lib/perl5/site_perl/jac_perl/i386-linux-thread-multi   /usr/lib/perl5/site_perl/jac_perl/5.8.2   /usr/lib/perl5/site_perl/jac_perl/5.8.1   /usr/lib/perl5/site_perl/jac_perl/5.8.0   /usr/lib/perl5/site_perl/jac_perl   /usr/lib/perl5/5.8.3/i386-linux-thread-multi   /usr/lib/perl5/5.8.3   /usr/lib/perl5/site_perl/5.8.3/i386-linux-thread-multi   /usr/lib/perl5/site_perl/5.8.2/i386-linux-thread-multi   /usr/lib/perl5/site_perl/5.8.1/i386-linux-thread-multi   /usr/lib/perl5/site_perl/5.8.0/i386-linux-thread-multi   /usr/lib/perl5/site_perl/5.8.3   /usr/lib/perl5/site_perl/5.8.2   /usr/lib/perl5/site_perl/5.8.1   /usr/lib/perl5/site_perl/5.8.0   /usr/lib/perl5/site_perl   /usr/lib/perl5/vendor_perl/5.8.3/i386-linux-thread-multi   /usr/lib/perl5/vendor_perl/5.8.2/i386-linux-thread-multi   /usr/lib/perl5/vendor_perl/5.8.1/i386-linux-thread-multi   /usr/lib/perl5/vendor_perl/5.8.0/i386-linux-thread-multi   /usr/lib/perl5/vendor_perl/5.8.3   /usr/lib/perl5/vendor_perl/5.8.2   /usr/lib/perl5/vendor_perl/5.8.1   /usr/lib/perl5/vendor_perl/5.8.0   /usr/lib/perl5/vendor_perl   .

Environment for perl v5.8.3​:   HOME=/home/chah   LANG=en_GB.iso88591   LANGUAGE (unset)   LD_LIBRARY_PATH=/jet/share/lib​:/usr/local/lib​:/usr/local/matlab/extern/lib/glnx86   LOGDIR (unset)   PATH=/usr/kerberos/bin​:/usr/bin​:/bin​:/usr/X11R6/bin​:/usr/local/bin​:/jet/share/root/bin​:/jet/share/bin​:/usr/lib/openoffice/program​:.​:/home/chah/bin   PERL5LIB=​:/usr/lib/perl5/site_perl/jac_perl   PERL_BADLANG (unset)   SHELL=/bin/bash

p5pRT commented 20 years ago

From @rgs

perl@​pythontech.co.uk (via RT) wrote​:

# 13 characters of junk are printed. # I expect nothing to be printed.

$data = "13 characters"; $data = undef;

open(MEM\,'\<'\,\$data) or die "Fail​: $!\n"; while (\) { print; }

I committed the following fix to the development branch of perl. It's not perfectly clean but it's conservative.

Change 23340 by rgs@​valis on 2004/09/30 15​:12​:29

  A fix for [perl #31692] : as PerlIO​::scalar accesses directly the   PV of the scalar it reads from\, avoid to read it when it's an   undefined PV.

Affected files ...

... //depot/perl/ext/PerlIO/scalar/scalar.xs#10 edit ... //depot/perl/ext/PerlIO/t/scalar.t#10 edit

Differences ...

==== //depot/perl/ext/PerlIO/scalar/scalar.xs#10 (text) ====

@​@​ -39\,7 +39\,7 @​@​   }   SvUPGRADE(s->var\, SVt_PV);   code = PerlIOBase_pushed(aTHX_ f\, mode\, Nullsv\, tab); - if ((PerlIOBase(f)->flags) & PERLIO_F_TRUNCATE) + if (!SvOK(s->var) || (PerlIOBase(f)->flags) & PERLIO_F_TRUNCATE)   SvCUR(s->var) = 0;   if ((PerlIOBase(f)->flags) & PERLIO_F_APPEND)   s->posn = SvCUR(s->var);

==== //depot/perl/ext/PerlIO/t/scalar.t#10 (text) ====

@​@​ -15\,7 +15\,7 @​@​ }

$| = 1; -print "1..25\n"; +print "1..26\n";

my $fh; my $var = "ok 2\n"; @​@​ -143\,3 +143\,9 @​@​   close $fh;   print $ok ? "ok 25\n" : "not ok 25\n"; } + +my $data = "a non-empty PV"; +$data = undef; +open(MEM\, '\<'\, \$data) or die "Fail​: $!\n"; +my $x = join ''\, \; +print $x eq '' ? "ok 26\n" : "not ok 26\n";

p5pRT commented 20 years ago

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

p5pRT commented 20 years ago

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