Re: @- Bug on the loose, lets isolate it

I quote from perlvar
"@- $-[0] is the offset of the start of the last successful match. "$-["n"]" is the offset of the start of the substring matched by n-th subpattern, or undef if the subpattern did not match."

So, in my understanding you really wanted to print $-[0] isn't it? You may run this:

use strict;
use warnings;

my $string = "abc";

while( $string =~ /c/g ) {
    print "$-[0]\n";
}
[download]

and get "2", and:

use strict;
use warnings;

my $string = "abc";

while( $string =~ /c/g ) {
    print "@-\n";
}
[download]

I get:

Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
Use of uninitialized value in join or string at /tmp/bug1.pl line 7.
2
[download]

perl version:

Summary of my perl5 (revision 5 version 8 subversion 5) configuration:
  Platform:
    osname=linux, osvers=2.6.9, archname=i686-linux-thread-multi
    uname='linux gnistorica 2.6.9 #1 mon nov 29 11:26:11 eet 2004 i686
+ intel(r) pentium(r) 4 cpu 2.80ghz genuineintel gnulinux '
    config_args='-des -Darchname=i686-linux-thread -Dcccdlflags=-fPIC 
+-Dccdlflags=-rdynamic -Dcc=gcc -Dprefix=/usr -Dvendorprefix=/usr -Dsi
+teprefix=/usr -Dlocincpth=  -Doptimize=-O3 -mcpu=i686 -fomit-frame-po
+inter -pipe -Duselargefiles -Dd_semctl_semun -Dscriptdir=/usr/bin -Dm
+an1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dinstallman
+1dir=/usr/share/man/man1 -Dinstallman3dir=/var/tmp/portage/perl-5.8.5
+-r5/image//usr/share/man/man3 -Dman1ext=1 -Dman3ext=3pm -Dinc_version
+_list=5.8.0 5.8.0/i686-linux-thread-multi 5.8.2 5.8.2/i686-linux-thre
+ad-multi 5.8.4 5.8.4/i686-linux-thread-multi  -Dcf_by=Gentoo -Ud_csh 
+-Dusethreads -Di_ndbm -Di_gdbm -Di_db'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=define use5005threads=undef useithreads=define usemulti
+plicity=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
+ -fno-strict-aliasing -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=6
+4',
    optimize='-O3 -mcpu=i686 -fomit-frame-pointer -pipe',
    cppflags='-DPERL5 -D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -
+fno-strict-aliasing -pipe'
    ccversion='', gccversion='3.3.5  (Gentoo Linux 3.3.5-r1, ssp-3.3.2
+-3, pie-8.7.7.1)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1
+2
    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=-lpthread -lnsl -lndbm -lgdbm -ldb -ldl -lm -lcrypt -lutil -l
+c
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=/lib/libc-2.3.4.so, so=so, useshrplib=false, libperl=libperl.
+a
    gnulibc_version='2.3.4'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynami
+c'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'


Characteristics of this binary (from libperl):
  Compile-time options: MULTIPLICITY USE_ITHREADS USE_LARGE_FILES PERL
+_IMPLICIT_CONTEXT
  Built under linux
  Compiled at Mar 15 2005 11:11:33
  @INC:
    /etc/perl
    /usr/lib/perl5/site_perl/5.8.5/i686-linux-thread-multi
    /usr/lib/perl5/site_perl/5.8.5
    /usr/lib/perl5/site_perl/5.8.4
    /usr/lib/perl5/site_perl/5.8.4/i686-linux-thread-multi
    /usr/lib/perl5/site_perl
    /usr/lib/perl5/vendor_perl/5.8.5/i686-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.8.5
    /usr/lib/perl5/vendor_perl
    /usr/lib/perl5/5.8.5/i686-linux-thread-multi
    /usr/lib/perl5/5.8.5
    /usr/local/lib/site_perl
    /usr/lib/perl5/site_perl/5.8.4
    /usr/lib/perl5/site_perl/5.8.4/i686-linux-thread-multi
[download]

Dodge This!

Comment on Re: @- Bug on the loose, lets isolate it Select or Download Code

Replies are listed 'Best First'.
Re^2: @- Bug on the loose, lets isolate it by thor (Priest) on May 30, 2005 at 16:17 UTC
I think the point is not what the @- array contains, but that it contains anything at all. The supplied regex doesn't do any capturing, so the @- array should be empty. What we're seeing is that perl is creating a very large array for no reason. Doing so takes time, thus slowing down programs where it shouldn't. That's a Bad Thing. thor `Feel the white light, the light within Be your own disciple, fan the sparks of will For all of us waiting, your kingdom will come`	[reply]
Re^3: @- Bug on the loose, lets isolate it by Ultra (Hermit) on May 30, 2005 at 17:39 UTC
Good point :-) Dodge This!	[reply]
Re^3: @- Bug on the loose, lets isolate it by diotalevi (Canon) on Jun 02, 2005 at 13:16 UTC
Both `@-` and `@+` should contain at least one element each to show where the start and end of the match is. You're supposed to be able to derive $& from `substr( ..., $-[0], $+[0] - $-[0] )`.	[reply] [d/l] [select]