[perl #23578] Symbol::delete_package permanently deletes namespace
David Coppit
# Please include the string: [perl #23578]
# in the subject line of all future correspondence about this issue.
# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=23578 >
This is a bug report for perl from per...@coppit.org,
generated with the help of perlbug 1.34 running under perl v5.8.0.
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[Please enter your report here]
When running the following script,
use Symbol;
require Storable;
Symbol::delete_package('Storable');
# Delete everything just to be safe.
map { delete $INC{$_} } keys %INC;
require Storable;
Storable::freeze([1,2,3]);
I get the following error:
Undefined subroutine &Storable::freeze called at test.pl line 12.
I was expecting the freeze function to be available after require'ing
Storable the second time. (i.e. no error)
[Please do not change anything below this line]
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---
Flags:
category=core
severity=low
---
Site configuration information for perl v5.8.0:
Configured by bhcompile at Sun Sep 1 23:55:07 EDT 2002.
Summary of my perl5 (revision 5.0 version 8 subversion 0) configuration:
Platform:
osname=linux, osvers=2.4.18-11smp, archname=i386-linux-thread-multi
uname='linux daffy.perf.redhat.com 2.4.18-11smp #1 smp thu aug 15 06:41:59 edt 2002 i686 i686 i386 gnulinux '
config_args='-des -Doptimize=-O2 -march=i386 -mcpu=i686 -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'
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 -fno-strict-aliasing -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
optimize='-O2 -march=i386 -mcpu=i686',
cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -I/usr/include/gdbm'
ccversion='', gccversion='3.2 20020822 (Red Hat Linux Rawhide 3.2-5)', 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 -lpthread -lc -lcrypt -lutil
perllibs=-lnsl -ldl -lm -lpthread -lc -lcrypt -lutil
libc=/lib/libc-2.2.92.so, so=so, useshrplib=true, libperl=libperl.so
gnulibc_version='2.2.92'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic -Wl,-rpath,/usr/lib/perl5/5.8.0/i386-linux-thread-multi/CORE'
cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'
Locally applied patches:
---
@INC for perl v5.8.0:
/usr/lib/perl5/5.8.0/i386-linux-thread-multi
/usr/lib/perl5/5.8.0
/usr/lib/perl5/site_perl/5.8.0/i386-linux-thread-multi
/usr/lib/perl5/site_perl/5.8.0
/usr/lib/perl5/site_perl
/usr/lib/perl5/vendor_perl/5.8.0/i386-linux-thread-multi
/usr/lib/perl5/vendor_perl/5.8.0
/usr/lib/perl5/vendor_perl
.
---
Environment for perl v5.8.0:
HOME=/home/david
LANG=en_US
LANGUAGE (unset)
LD_LIBRARY_PATH (unset)
LOGDIR (unset)
PATH=/usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/home/david/bin
PERLDB_OPTS=HighBit=1
PERL_BADLANG (unset)
SHELL=/bin/bash
Rafael Garcia-Suarez
>
> When running the following script,
>
> use Symbol;
>
> require Storable;
> Symbol::delete_package('Storable');
>
> # Delete everything just to be safe.
> map { delete $INC{$_} } keys %INC;
>
> require Storable;
> Storable::freeze([1,2,3]);
>
> I get the following error:
>
> Undefined subroutine &Storable::freeze called at test.pl line 12.
>
> I was expecting the freeze function to be available after require'ing
> Storable the second time. (i.e. no error)
I will try to explain what I think is happening here with a simpler
example :
Let x.pl contain :
use Symbol;
Symbol::delete_package('A');
require A;
A::foo();
And A.pm defining a single subroutine :
package A;
sub foo {print "foo\n"}
1;
When x.pl is compiled, the %A:: stash is created to put an empty
placeholder for the foo() subroutine, at compile time. This placeholder
is supposed to be replaced by the actual subroutine when A is loaded (at
runtime, since we use "require A".)
However the placeholder is wiped out by delete_package(), and loading
A.pm recreates a new A stash, but not necessarily with A::foo at the same
memory address. And the original A::foo() call in x.pl has already been
optimized to a glob pointer, since perl is smart enough to avoid a stash
lookup each time it calls a subroutine. This glob has been undefined
by delete_package().
And indeed, changing the A::foo() call to
&{"A::foo"}();
makes it work, because this forces the symbolic lookup.
I don't know how to fix this.
Rafael Garcia-Suarez
>
> I will try to explain what I think is happening here with a simpler
> example :
I've now added a BUGS section to the docs for Symbol about this
overpowerful effect of delete_package(). While I was at it, I added
some tests for this function as well. (change 20922.)