Closed p5pRT closed 11 years ago
p5pRT
commented
11 years ago Running `perl X.pl` or `perl -c X.pl` never halts\, where X.pl contains the following single line:
e's a cm.."frus.."
p5pRT
commented
11 years ago On Tue Aug 06 12:26:27 2013\, ericp wrote:
This is a bug report for perl from ericp@activestate.com\, generated with the help of perlbug 1.39 running under perl 5.14.2.
----------------------------------------------------------------- [Please describe your issue here]
Running `perl X.pl` or `perl -c X.pl` never halts\, where X.pl contains the following single line:
e's a cm.."frus.."
[Please do not change anything below this line] ----------------------------------------------------------------- --- Flags: category=core severity=low --- Site configuration information for perl 5.14.2:
Configured by Debian Project at Tue Nov 27 00:34:23 UTC 2012.
Summary of my perl5 (revision 5 version 14 subversion 2) configuration:
Platform: osname=linux\, osvers=2.6.42-32-generic\, archname=x86_64-linux- gnu-thread-multi uname='linux allspice 2.6.42-32-generic #51-ubuntu smp wed sep 26 21:33:09 utc 2012 x86_64 x86_64 x86_64 gnulinux ' config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.14 -Darchlib=/usr/lib/perl/5.14 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.14.2 -Dsitearch=/usr/local/lib/perl/5.14.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dlibperl=libperl.so.5.14.2 -des' hint=recommended\, useposix=true\, d_sigaction=define useithreads=define\, usemultiplicity=define useperlio=define\, d_sfio=undef\, uselargefiles=define\, usesocks=undef use64bitint=define\, use64bitall=define\, uselongdouble=undef usemymalloc=n\, bincompat5005=undef Compiler: cc='cc'\, ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'\, optimize='-O2 -g'\, cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include' ccversion=''\, gccversion='4.6.3'\, gccosandvers='' intsize=4\, longsize=8\, ptrsize=8\, doublesize=8\, byteorder=12345678 d_longlong=define\, longlongsize=8\, d_longdbl=define\, longdblsize=16 ivtype='long'\, ivsize=8\, nvtype='double'\, nvsize=8\, Off_t='off_t'\, lseeksize=8 alignbytes=8\, prototype=define Linker and Libraries: ld='cc'\, ldflags =' -fstack-protector -L/usr/local/lib' libpth=/usr/local/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /usr/lib libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt perllibs=-ldl -lm -lpthread -lc -lcrypt libc=\, so=so\, useshrplib=true\, libperl=libperl.so.5.14.2 gnulibc_version='2.15' Dynamic Linking: dlsrc=dl_dlopen.xs\, dlext=so\, d_dlsymun=undef\, ccdlflags='-Wl\,-E' cccdlflags='-fPIC'\, lddlflags='-shared -O2 -g -L/usr/local/lib -fstack-protector'
Locally applied patches:
--- @INC for perl 5.14.2: /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl .
--- Environment for perl 5.14.2: HOME=/home/ericp LANG=en_CA.UTF-8 LANGUAGE=en_CA:en LD_LIBRARY_PATH (unset) LOGDIR (unset) PATH=/home/ericp/.local/bin:/home/ericp/opt/node- 0.8.0/bin:/home/ericp/opt/ActivePython-
2.7.2.5/bin:/home/ericp/bin:/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/home/ericp/svn/apps/komodo/util/black:/home/ericp/opt/ActivePython- 3.2.2.3/bin:/home/ericp/opt/ActiveTcl8.5.12.0.296033/bin PERL_BADLANG (unset) SHELL=/bin/bash
This isn't really an infinite loop\, it's just going to take a long\, long time before it finishes. The "e's a" is a red herring (it's actually calling the method e::s on 'a')\, the important bit is the cm.."frus.."\, which is creating a list of strings from "cm" to "zzzzzz" using the magic autoincrement.
This might be easier to see if you "deparse" it:
a->e::s( "cm".."frus.." );
Whose non-weird cousin might look like this:
Alphabet->fill( "a".."z" );
This is similar to other constructs that take a long time\, like 1..1e10 or (1..100) x 1e8
Even though the autoincrement will try reaching "frus.." and fail\, since it'll always go through a-z and never use a period\, it's not an infinite loop because after "zzzzzz" it'll get "aaaaaaa"\, which is longer than the original string\, and stop there.
So I think this ticket can be closed\, since it's not really a bug (just a shoot-your-own-foot\, as it were).
--hugmeir
p5pRT
commented
11 years ago The RT System itself - Status changed from 'new' to 'open'
p5pRT
commented
11 years ago @cpansprout - Status changed from 'open' to 'rejected'
p5pRT
commented
11 years ago On Tue\, Aug 6\, 2013 at 7:49 PM\, Brian Fraser via RT \< perlbug-followup@perl.org> wrote:
On Tue Aug 06 12:26:27 2013\, ericp wrote:
This is a bug report for perl from ericp@activestate.com\, generated with the help of perlbug 1.39 running under perl 5.14.2.
Running `perl X.pl` or `perl -c X.pl` never halts\, where X.pl contains the following single line:
e's a cm.."frus.."
This isn't really an infinite loop\, it's just going to take a long\, long time before it finishes. The "e's a" is a red herring (it's actually calling the method e::s on 'a')\, the important bit is the cm.."frus.."\, which is creating a list of strings from "cm" to "zzzzzz" using the magic autoincrement.
This might be easier to see if you "deparse" it:
a->e::s( "cm".."frus.." );
Whose non-weird cousin might look like this:
Alphabet->fill( "a".."z" );
This is similar to other constructs that take a long time\, like 1..1e10 or (1..100) x 1e8
Even though the autoincrement will try reaching "frus.." and fail\, since it'll always go through a-z and never use a period\, it's not an infinite loop because after "zzzzzz" it'll get "aaaaaaa"\, which is longer than the original string\, and stop there.
And the reason C\<\< perl -c X.pl >> never ends is that CONST..CONST is flattened at compile-time.
p5pRT
commented
11 years ago Thanks for the explanation. I was thrown off by the second pair of ".."\, but that's just used to extend the second argument to ".." so it will take a long time to produce the list.
A more straightforward "f(cm..'fsur..')" exhibits the same behavior; yes\, that Ada-influenced single-quote was just a red herring.
p5pRT
commented
11 years ago On Tue\, Aug 06\, 2013 at 11:01:52PM -0400\, Eric Brine wrote:
On Tue\, Aug 6\, 2013 at 7:49 PM\, Brian Fraser via RT \< perlbug-followup@perl.org> wrote:
On Tue Aug 06 12:26:27 2013\, ericp wrote:
This is a bug report for perl from ericp@activestate.com\, generated with the help of perlbug 1.39 running under perl 5.14.2.
Running `perl X.pl` or `perl -c X.pl` never halts\, where X.pl contains the following single line:
e's a cm.."frus.."
This isn't really an infinite loop\, it's just going to take a long\, long time before it finishes. The "e's a" is a red herring (it's actually calling the method e::s on 'a')\, the important bit is the cm.."frus.."\, which is creating a list of strings from "cm" to "zzzzzz" using the magic autoincrement.
This might be easier to see if you "deparse" it:
a->e::s( "cm".."frus.." );
Whose non-weird cousin might look like this:
Alphabet->fill( "a".."z" );
This is similar to other constructs that take a long time\, like 1..1e10 or (1..100) x 1e8
Even though the autoincrement will try reaching "frus.." and fail\, since it'll always go through a-z and never use a period\, it's not an infinite loop because after "zzzzzz" it'll get "aaaaaaa"\, which is longer than the original string\, and stop there.
And the reason C\<\< perl -c X.pl >> never ends is that CONST..CONST is flattened at compile-time.
It would end (rather early\, with an out of memory error) if this code in pp_flop knew how to (attempt to) pre-extend the stack:
STRLEN len\, llen; const char * const lpv = SvPV_nomg_const(left\, llen); const char * const tmps = SvPV_nomg_const(right\, len);
SV *sv = newSVpvn_flags(lpv\, llen\, SvUTF8(left)|SVs_TEMP); while (!SvNIOKp(sv) && SvCUR(sv) \<= len) { XPUSHs(sv); if (strEQ(SvPVX_const(sv)\,tmps)) break; sv = sv_2mortal(newSVsv(sv)); sv_inc(sv); }
but it's quite hard to work out how many entries there will be in the range. For example\, "cm" .. ".." will be different from "c1" .. "..".
Nicholas Clark
Migrated from rt.perl.org#119181 (status was 'rejected')
Searchable as RT119181$