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Nov 27, 2007, 9:30 PM
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[perl #47906] Split does not always strip trailing empty fields
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# New Ticket Created by John Wiersba
# Please include the string: [perl #47906]
# in the subject line of all future correspondence about this issue.
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=47906 >
[Please enter your report here]
Question: Under which conditions does split() strip trailing null (empty)
fields? Apparently only under at least one of these conditions:
1) When the return value of split is used directly as the return value of
a function.
2) When the return value of split is assigned to a list of variables which
includes an array variable.
Test case showing the inconsistency of split() striping trailing null fields
sometimes and not others:
#!/usr/bin/perl -w
use strict;
sub fn {
split /:/, ":x:";
}
sub printit {
$_ = defined $_ ? $_ : "UNDEF" for @_;
local $" = "><";
print "<$_>" for @_;
print "\n";
}
my ($a, $b, $c, $d, @out);
($a, $b, $c ) = fn; printit $a, $b, $c;
($a, $b, $c ) = split /:/, ":x:"; printit $a, $b, $c;
($a, $b, $c, $d ) = fn; printit $a, $b, $c, $d;
($a, $b, $c, $d ) = split /:/, ":x:"; printit $a, $b, $c, $d;
($a, @out) = fn; printit $a, $#out, @out;
($a, @out) = split /:/, ":x:"; printit $a, $#out, @out;
($a, $b, @out) = fn; printit $a, $b, $#out, @out;
($a, $b, @out) = split /:/, ":x:"; printit $a, $b, $#out, @out;
($a, $b, $c, @out) = fn; printit $a, $b, $c, $#out, @out;
($a, $b, $c, @out) = split /:/, ":x:"; printit $a, $b, $c, $#out, @out;
Output:
<><x><UNDEF>
<><x><> <= NOTE: unexpected empty field after "x"
<><x><UNDEF><UNDEF>
<><x><><UNDEF> <= NOTE: unexpected empty field after "x"
<><0><x>
<><0><x>
<><x><-1>
<><x><-1>
<><x><UNDEF><-1>
<><x><UNDEF><-1>
[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
category=core
severity=medium
---
Site configuration information for perl v5.8.8:
Configured by Debian Project at Tue Mar 6 01:52:23 UTC 2007.
Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
Platform:
osname=linux, osvers=2.6.15.7, archname=i486-linux-gnu-thread-multi
uname='linux rothera 2.6.15.7 #1 smp sat sep 30 10:21:42 utc 2006 i686 gnuli++ nux '
config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-f++ PIC -Darchname=i486-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.8 -Da++ rchlib=/usr/lib/perl/5.8 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dv++ endorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/p++ erl/5.8.8 -Dsitearch=/usr/local/lib/perl/5.8.8 -Dman1dir=/usr/share/man/man1 ++ -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir++ =/usr/local/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pa++ ger -Uafs -Ud_csh -Uusesfio -Uusenm -Duseshrplib -Dlibperl=libperl.so.5.8.8 -++ Dd_dosuid -des'
hint=recommended, useposix=true, d_sigaction=define
usethreads=define use5005threads=undef useithreads=define usemultiplicity=de++ fine
useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
use64bitint=undef use64bitall=undef uselongdouble=undef
usemymalloc=n, bincompat5005=undef
Compiler:
cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -++ fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OF++ FSET_BITS=64',
optimize='-O2',
cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -fno-stric++ t-aliasing -pipe -I/usr/local/include'
ccversion='', gccversion='4.1.2 (Ubuntu 4.1.2-0ubuntu4)', 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='cc', ldflags =' -L/usr/local/lib'
libpth=/usr/local/lib /lib /usr/lib
libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
perllibs=-ldl -lm -lpthread -lc -lcrypt
libc=/lib/libc-2.5.so, so=so, useshrplib=true, libperl=libperl.so.5.8.8
gnulibc_version='2.5'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'
Locally applied patches:
---
@INC for perl v5.8.8:
/jrw/mdst/sh/../lib
/usr/local/lib/perl5/site_perl/5.8.0
/etc/perl
/usr/local/lib/perl/5.8.8
/usr/local/share/perl/5.8.8
/usr/lib/perl5
/usr/share/perl5
/usr/lib/perl/5.8
/usr/share/perl/5.8
/usr/local/lib/site_perl
.
---
Environment for perl v5.8.8:
HOME=/home/jrw
LANG (unset)
LANGUAGE (unset)
LC_ALL=C
LD_LIBRARY_PATH (unset)
LOGDIR (unset) PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin:/home/jrw/sh:/home/jrw/bin:++ /jrw/mdst/sh:/jrw/mdst/sh/GAMES:/jrw/mdst/binu:/jrw/mdst/binw:.
PERL5LIB=/jrw/mdst/sh/../lib:/usr/local/lib/perl5/site_perl/5.8.0
PERLDB_OPTS=NonStop frame=2
PERL_BADLANG (unset)
SHELL=/bin/ksh
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