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Apr 10, 2008, 6:41 AM
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[perl #52702] Consistent localization between foreach (...) and while (<fh>)
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# New Ticket Created by "Ed Avis"
# Please include the string: [perl #52702]
# in the subject line of all future correspondence about this issue.
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=52702 >
This is a bug report for perl from eda [at] waniasset,
generated with the help of perlbug 1.36 running under perl 5.10.0.
-----------------------------------------------------------------
[Please enter your report here]
This is an enhancement request for a small change to the perl
language. A 'foreach (1, 2, 3) {}' loop implicitly localizes $_ but a
'while (<$fh>)' does not. I suggest changing the semantics of 'while
(<$fh>)' so it does the same localization, or if this is too much to
stomach, adding a warning if the 'while (<$fh>)' construct is used in
a subroutine without localizing $_ first.
#!/usr/bin/perl
use warnings;
use strict;
use 5.010;
$_ = 'x';
open FH, '<', '/dev/null' or die;
while (<FH>) {}
say defined($_) ? "defined: $_" : 'not defined';
$_ = 'y';
foreach (1, 2, 3) {}
say defined($_) ? "defined: $_" : 'not defined';
This shows that a while-loop doesn't localize $_ but a foreach-loop
does. This is the documented behaviour, so this is not a bug. It
might be worth changing it for perl 5.12.
sub my_sub {
open my $fh, '<', 'some_file' or die;
while (<$fh>) { say 'hi' }
}
This code doesn't produce a warning on current perl, but I think it
should say
warning: while (<filehandle>) implicitly sets $_, but it is not
localized first in subroutine my_sub
or some similar warning.
[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
category=core
severity=wishlist
---
Site configuration information for perl 5.10.0:
Configured by Red Hat, Inc. at Wed Dec 19 14:44:53 GMT 2007.
Summary of my perl5 (revision 5 version 10 subversion 0) configuration:
Platform:
osname=linux, osvers=2.6.23.8-63.fc8, archname=i386-linux-thread-multi
uname='linux localhost.localdomain 2.6.23.8-63.fc8 #1 smp wed nov 21 18:51:08 est 2007 i686 gnulinux '
config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -Dversion=5.10.0 -Dmyhostname=localhost -Dperladmin=root [at] localhos -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=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dd_gethostent_r_proto -Ud_endhostent_r_proto -Ud_sethostent_r_proto -Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_proto -Ud_setservent_r_proto -Dscriptdir=/usr/bin'
hint=recommended, useposix=true, d_sigaction=define
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 -DDEBUGGING -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables',
cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBUGGING -fno-strict-aliasing -pipe -I/usr/local/include -I/usr/include/gdbm'
ccversion='', gccversion='4.1.2 20070925 (Red Hat 4.1.2-33)', 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=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc
perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
libc=/lib/libc-2.7.so, so=so, useshrplib=true, libperl=libperl.so
gnulibc_version='2.7'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -Wl,-rpath,/usr/lib/perl5/5.10.0/i386-linux-thread-multi/CORE'
cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables -L/usr/local/lib'
Locally applied patches:
---
@INC for perl 5.10.0:
/home/eda/lib/perl5/5.10.0/i386-linux-thread-multi
/home/eda/lib/perl5/5.10.0
/home/eda/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi
/home/eda/lib/perl5/site_perl/5.10.0
/usr/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi
/usr/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi
/usr/lib/perl5/site_perl/5.10.0
/usr/lib/perl5/vendor_perl/5.10.0/i386-linux-thread-multi
/usr/lib/perl5/vendor_perl/5.10.0/i386-linux-thread-multi
/usr/lib/perl5/vendor_perl/5.10.0
/usr/lib/perl5/5.10.0/i386-linux-thread-multi
/usr/lib/perl5/5.10.0
/usr/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi
/usr/lib/perl5/site_perl/5.10.0
/usr/lib/perl5/site_perl/5.8.8
/usr/lib/perl5/site_perl/5.8.7
/usr/lib/perl5/site_perl/5.8.6
/usr/lib/perl5/site_perl/5.8.5
/usr/lib/perl5/site_perl/5.6.1
/usr/lib/perl5/site_perl
/usr/lib/perl5/vendor_perl/5.10.0/i386-linux-thread-multi
/usr/lib/perl5/vendor_perl/5.10.0
/usr/lib/perl5/vendor_perl/5.8.8
/usr/lib/perl5/vendor_perl/5.8.7
/usr/lib/perl5/vendor_perl/5.8.6
/usr/lib/perl5/vendor_perl/5.8.5
/usr/lib/perl5/vendor_perl
.
---
Environment for perl 5.10.0:
HOME=/home/eda
LANG=en_GB.UTF-8
LANGUAGE (unset)
LC_COLLATE=C
LC_CTYPE=en_GB.UTF-8
LC_MESSAGES=en_GB.UTF-8
LC_MONETARY=en_GB.UTF-8
LC_NUMERIC=en_GB.UTF-8
LC_TIME=en_GB.UTF-8
LD_LIBRARY_PATH (unset)
LOGDIR (unset)
PATH=/home/eda/bin:/home/eda/bin:/usr/lib/qt-3.3/bin:/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/home/eda/bin
PERL5LIB=/home/eda/lib/perl5/5.10.0:/home/eda/lib/perl5/site_perl/5.10.0:/usr/lib/perl5/site_perl/5.10.0/i386-linux-thread-multi:/usr/lib/perl5/site_perl/5.10.0:/usr/lib/perl5/vendor_perl/5.10.0/i386-linux-thread-multi:/usr/lib/perl5/vendor_perl/5.10.0
PERL_BADLANG (unset)
SHELL=/bin/bash
--
Ed Avis <eda [at] waniasset>
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[perl #52702] Consistent localization between foreach (...) and while (<fh>)
