[perl #96538] Closures returned from threads don't wrap around the right lexicals

# New Ticket Created by  perl@profvince.com 
# Please include the string:  [perl #96538]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=96538 >




This is a bug report for perl from perl@profvince.com,
generated with the help of perlbug 1.39 running under perl 5.14.1.


-----------------------------------------------------------------
[Please describe your issue here]

On join, threads.pm calls sv_dup on the values returned to the caller
thread, but with an empty pointer table. This is wrong, because when a
code reference is returned, sv_dup is then unable to relink the variables
captured by the coderef to their proper incarnation from the parent
thread. Here's an example :

perl -Mthreads -wE'my $x; my $set_x = sub { $x = shift }; $set_x->(123); 
say $x; threads->create(sub { return $set_x })->join->(456); say $x'

This should print 123 and then 456, but it prints 123. The duplicated copy
of $set_x returned by the thread assigns to a scalar that is not the local
instance of $x.


[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
     category=core
     severity=medium
---
Site configuration information for perl 5.14.1:

Configured by vince at Fri Jul  8 19:46:39 CEST 2011.

Summary of my perl5 (revision 5 version 14 subversion 1) configuration:

   Platform:
     osname=linux, osvers=2.6.39.1-fuuka.profvince.com, 
archname=x86_64-linux-thread-multi
     uname='linux fuuka 2.6.39.1-fuuka.profvince.com #1 smp fri jun 10 
20:18:17 cest 2011 x86_64 intel(r) core(tm)2 duo cpu e6750 @ 2.66ghz 
genuineintel gnulinux '
     config_args='-Doptimize=-march=core2 -O3 -fomit-frame-pointer 
-ftree-vectorize -ftree-vectorizer-verbose=1 -pipe -DNDEBUG -des 
-Dusedevel -Dman1dir=none -Dman3dir=none -Dcf_email=vpit@cpan.org 
-Dmydomain=fuuka.profvince.com -DEBUGGING=none -Dusethreads 
-Dusemmorebits -Dprefix=/home/vince/perl/builds/thr/64/5.14.1'
     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 -fno-strict-aliasing 
-pipe -fstack-protector -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
     optimize='-march=core2 -O3 -fomit-frame-pointer -ftree-vectorize 
-ftree-vectorizer-verbose=1 -pipe -DNDEBUG',
     cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe 
-fstack-protector'
     ccversion='', gccversion='4.5.2', 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/../lib64 /usr/lib/../lib64 /lib /usr/lib 
/lib64 /usr/lib64 /usr/local/lib64
     libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc 
-lgdbm_compat
     perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
     libc=/lib/libc-2.13.so, so=so, useshrplib=false, libperl=libperl.a
     gnulibc_version='2.13'
   Dynamic Linking:
     dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
     cccdlflags='-fPIC', lddlflags='-shared -march=core2 -O3 
-fomit-frame-pointer -ftree-vectorize -ftree-vectorizer-verbose=1 -pipe 
-DNDEBUG -L/usr/local/lib -fstack-protector'

Locally applied patches:


---
@INC for perl 5.14.1:
     
/home/vince/perl/builds/thr/64/5.14.1/lib/site_perl/5.14.1/x86_64-linux-thread-multi
     /home/vince/perl/builds/thr/64/5.14.1/lib/site_perl/5.14.1
     
/home/vince/perl/builds/thr/64/5.14.1/lib/5.14.1/x86_64-linux-thread-multi
     /home/vince/perl/builds/thr/64/5.14.1/lib/5.14.1
     .

---
Environment for perl 5.14.1:
     HOME=/home/vince
     LANG=fr_FR.UTF-8
     LANGUAGE (unset)
     LC_ALL=fr_FR.UTF-8
     LD_LIBRARY_PATH (unset)
     LOGDIR (unset)
     
PATH=/home/vince/bin:/home/vince/perl/builds/bin:/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/x86_64-pc-linux-gnu/gcc-bin/4.5.2:/opt/intel/cce/10.1.018/bin:/usr/games/bin
     PERL_BADLANG (unset)
     SHELL=/bin/bash

• [perl #96538] Closures returned from threads don't wrap around the right lexicals by perl @ profvince . com
• Re: [perl #96538] Closures returned from threads don't wrap aroundthe right lexicals by Jerry D. Hedden