[perl #21053] Lexical scoping bug concerning eval

# New Ticket Created by  marcello@hummer.stanford.edu 
# Please include the string:  [perl #21053]
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# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=21053 >


Hi, I am reporting a lexical scoping bug of a nasty nature.
I am running Perl v5.6.1 on a redhat 7.3 i386-Linux platform.
Synopsis:
Given a variable in package B, used from package A, package A can't access it
in via an eval statement.

Example:
Here is the short and sweet (or not so sweet)! version:
__FILE__BEGINS__
#!/usr/bin/perl
package B;
my $answer = 42;
1;
package A;
sub fn{
	print "answer=" . eval ('$B::answer') . "\n";
	print "answer=" . eval ('package B; $answer') . "\n";
 }
1;
package main;
A::fn();
1;
__FILE__ENDS__
this prints:
answer=
answer=42

There is something way wrong as only the second one works!
However, there is more.
In additional testing with A and B in separate files, neither of them work!
A tgz of the three files (A.pm, B.pm, and main.pl) is attached.

I would very much appreciate to know the cause of this aberration, and have a
personal interest in knowing how and why this code fails, given that I want
to use the same trick on something a bit more complicated and was quite
chagrined that it didn't work.

I hope that this bug report will be of benefit to the Perl community.
-=+Marcello Mathias Herreshoff

P.S. output of perlbug -d
Site configuration information for perl v5.6.1:

Configured by bhcompile at Mon Apr  1 12:22:19 EST 2002.

Summary of my perl5 (revision 5.0 version 6 subversion 1) configuration:
  Platform:
    osname=linux, osvers=2.4.17-0.13smp, archname=i386-linux
    uname='linux daffy.perf.redhat.com 2.4.17-0.13smp #1 smp fri feb 1 10:30:48 est 2002 i686 unknown '
    config_args='-des -Doptimize=-O2 -march=i386 -mcpu=i686 -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dcccdlflags=-fPIC -Dinstallprefix=/usr -Dprefix=/usr
-Darchna
me=i386-linux -Dvendorprefix=/usr -Dsiteprefix=/usr -Uusethreads -Uuseithreads -Uuselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Di_ndbm -Di_gdbm
-Di_s
hadow -Di_syslog -Dman3ext=3pm'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
    useperlio=undef d_sfio=undef uselargefiles=undef usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
  Compiler:
    cc='gcc', ccflags ='-fno-strict-aliasing -I/usr/local/include',
    optimize='-O2 -march=i386 -mcpu=i686',
    cppflags='-fno-strict-aliasing -I/usr/local/include'
    ccversion='', gccversion='2.96 20000731 (Red Hat Linux 7.2 2.96-109)', 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=4
    alignbytes=4, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -ldl -lm -lc -lcrypt -lutil
    perllibs=-lnsl -ldl -lm -lc -lcrypt -lutil
    libc=/lib/libc-2.2.5.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'

Locally applied patches:


---
@INC for perl v5.6.1:
    /usr/lib/perl5/5.6.1/i386-linux
    /usr/lib/perl5/5.6.1
    /usr/lib/perl5/site_perl/5.6.1/i386-linux
    /usr/lib/perl5/site_perl/5.6.1
    /usr/lib/perl5/site_perl/5.6.0/i386-linux
    /usr/lib/perl5/site_perl/5.6.0
    /usr/lib/perl5/site_perl
    /usr/lib/perl5/vendor_perl/5.6.1/i386-linux
    /usr/lib/perl5/vendor_perl/5.6.1
    /usr/lib/perl5/vendor_perl
    .

---
Environment for perl v5.6.1:
    HOME=/home/marcello
    LANG=en_US
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/home/marcello/prog/perl/:/home/marcello/bin:/home/marcello/prog/perl/:/home/marce
llo/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash



-- attachment  1 ------------------------------------------------------
url: http://rt.perl.org/rt2/attach/51331/39332/0a881f/bug.tgz

• [perl #21053] Lexical scoping bug concerning eval by perlbug-followup
• Re: [perl #21053] Lexical scoping bug concerning eval by Dave Mitchell