[perl #36586] $1 gets mysteriously unset when leaving 'for' block

2005-07-18 Thread via RT 
# New Ticket Created by  [EMAIL PROTECTED] 
# Please include the string:  [perl #36586]
# in the subject line of all future correspondence about this issue. 
# URL: https://rt.perl.org/rt3/Ticket/Display.html?id=36586 


This is a bug report for perl from [EMAIL PROTECTED],
generated with the help of perlbug 1.35 running under perl v5.8.4.


-
[Please enter your report here]

This test program:

my $foo = 'foo';
for ($foo) {
m!(\w+)! or die;
print \$1 has been set to: $1\n;
}
print \$1 is now: $1\n;

gives the output:

$1 has been set to: foo
$1 is now: 

Somehow, although $1 was set it has been changed back to undef on
exiting the 'for' block.  I don't see anything in perlre or perlvar
documenting this.

Surely only a regular expression match should do anything to change
the value of $1?

I have reproduced this on 5.8.4 and 5.8.7.

[Please do not change anything below this line]
-
---
Flags:
category=core
severity=medium
---
Site configuration information for perl v5.8.4:

Configured by ActiveState at Thu Jun  3 11:51:49 PDT 2004.

Summary of my perl5 (revision 5 version 8 subversion 4) configuration:
  Platform:
osname=linux, osvers=2.2.17, archname=i686-linux-thread-multi
uname='linux gimlet 2.2.17 #1 sun jun 25 09:24:41 est 2000 i686 unknown '
config_args='-ders -Dcc=gcc -Accflags=-DNO_HASH_SEED -Dusethreads 
-Duseithreads -Ud_sigsetjmp -Uinstallusrbinperl -Ulocincpth= -Uloclibpth= 
-Duselargefiles -Uusemallocwrap -Dinc_version_list=5.8.3/$archname 5.8.3 
5.8.2/$archname 5.8.2 5.8.1/$archname 5.8.1 5.8.0/$archname 5.8.0 -Duseshrplib 
-Dprefix=/usr/local/pkgs/ActivePerl-5.8.4.810 -Dcf_by=ActiveState [EMAIL 
PROTECTED]'
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 
-DNO_HASH_SEED -fno-strict-aliasing -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
optimize='-O2',
cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DNO_HASH_SEED 
-fno-strict-aliasing'
ccversion='', gccversion='2.95.2 2220 (Debian GNU/Linux)', 
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 =''
libpth=/lib /usr/lib /usr/local/lib
libs=-lnsl -lndbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc -lposix
perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc -lposix
libc=/lib/libc-2.1.3.so, so=so, useshrplib=true, libperl=libperl.so
gnulibc_version='2.1.3'
  Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E 
-Wl,-rpath,/usr/local/pkgs/ActivePerl-5.8.4.810/lib/5.8.4/i686-linux-thread-multi/CORE'
cccdlflags='-fpic', lddlflags='-shared'

Locally applied patches:
ACTIVEPERL_LOCAL_PATCHES_ENTRY
22751 Update to Test.pm 1.25
21540 Fix backward-compatibility issues in if.pm

---
@INC for perl v5.8.4:
/u/avised/lib/perl5/5.8.0
/u/avised/lib/perl5
/u/avised/lib/perl5/5.8.4
/u/avised/lib/perl5/site_perl/5.8.4
/u/avised/lib/perl5/site_perl/5.8.4/i386-linux
/u/avised/lib/perl5/site_perl/5.8.0
/u/avised/lib/perl5/site_perl
/u/avised/lib/5.8.4/i686-linux-thread-multi
/u/avised/lib/5.8.4
/u/avised/lib/site_perl/5.8.4/i686-linux-thread-multi
/u/avised/lib/site_perl/5.8.4
/u/avised/lib/site_perl/5.8.4/i386-linux
/u/avised/lib/site_perl/5.8.4/i686-linux-thread-multi
/u/avised/lib/site_perl/5.8.4
/u/avised/lib/site_perl/5.8.3/i686-linux-thread-multi
/u/avised/lib/site_perl/5.8.3
/u/avised/lib/site_perl
/u/avised/lib/site_perl/5.8.4/i686-linux-thread-multi

/usr/local/pkgs/ActivePerl-5.8.4.810/lib/site_perl/5.8.4/i686-linux-thread-multi
/usr/local/pkgs/ActivePerl-5.8.4.810/lib/site_perl/5.8.4
/prod/datatech/inferno/bin/scripts
/usr/local/pkgs/ActivePerl-5.8.4.810/lib/5.8.4/i686-linux-thread-multi
/usr/local/pkgs/ActivePerl-5.8.4.810/lib/5.8.4

/usr/local/pkgs/ActivePerl-5.8.4.810/lib/site_perl/5.8.4/i686-linux-thread-multi
/usr/local/pkgs/ActivePerl-5.8.4.810/lib/site_perl/5.8.4
/usr/local/pkgs/ActivePerl-5.8.4.810/lib/site_perl
.

---
Environment for perl v5.8.4:
HOME=/u/avised
LANG=en_US.UTF-8
LANGUAGE (unset)
LANGVAR=en_US.UTF-8

Re: [perl #36586] $1 gets mysteriously unset when leaving 'for' block

2005-07-18 Thread Michael G Schwern 
On Mon, Jul 18, 2005 at 01:41:52AM -0700, avised @ kbcfp. com wrote:
 This test program:
 
 my $foo = 'foo';
 for ($foo) {
 m!(\w+)! or die;
 print \$1 has been set to: $1\n;
 }
 print \$1 is now: $1\n;
 
 gives the output:
 
 $1 has been set to: foo
 $1 is now: 
 
 Somehow, although $1 was set it has been changed back to undef on
 exiting the 'for' block.  I don't see anything in perlre or perlvar
 documenting this.

Feature, not bug.

From perlre:

   The numbered match variables ($1, $2, $3, etc.) and the related punctu-
   ation set ($+, $, $`, $', and $^N) are all dynamically scoped until
   the end of the enclosing block or until the next successful match,
   whichever comes first.  (See Compound Statements in perlsyn.)

$1 and friends have an implicit local on them so they are localized to
a block.  Its been this way for a long time.

$ perl5.4.5 -wle '$_ = foo; { /(\w)/;  print $1 } print $1'
f
Use of uninitialized value at -e line 1.


-- 
Michael G Schwern [EMAIL PROTECTED] http://www.pobox.com/~schwern
'All anyone gets in a mirror is themselves,' she said. 'But what you
gets in a good gumbo is everything.'
-- Witches Abroad by Terry Prachett