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Smartmatch modifies array on failed match? #14746

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p5pRT opened this issue Jun 10, 2015 · 5 comments
Open

Smartmatch modifies array on failed match? #14746

p5pRT opened this issue Jun 10, 2015 · 5 comments
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distro-Linux type-core

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@p5pRT
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p5pRT commented Jun 10, 2015

Migrated from rt.perl.org#125377 (status was 'open')

Searchable as RT125377$
@p5pRT
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p5pRT commented Jun 10, 2015

From @wolfsage

Created by wolfsage@gmail.com

Perhaps this is expected undesirable behaviour or perhaps this
is a bug. Not sure​:

  mhorsfall@​dumai​:~$ perl -e '@​x[$b, $c] =~ "cat"; print 0+@​x, "\n";'
  0
  mhorsfall@​dumai​:~$ perl -e '@​x[$b, $c] ~~ "cat"; print 0+@​x, "\n";'
  Smartmatch is experimental at -e line 1.
  1

Perl Info 

Flags:
    category=core
    severity=low

Site configuration information for perl 5.20.1:

Configured by Debian Project at Fri Oct 10 14:16:26 UTC 2014.

Summary of my perl5 (revision 5 version 20 subversion 1) configuration:

  Platform:
    osname=linux, osvers=3.2.0-37-generic,
archname=x86_64-linux-gnu-thread-multi
    uname='linux batsu 3.2.0-37-generic #58-ubuntu smp thu jan 24
15:28:10 utc 2013 x86_64 x86_64 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN
-D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector-strong -Wformat
-Werror=format-security -Dldflags= -Wl,-Bsymbolic-functions
-Wl,-z,relro -Dlddlflags=-shared -Wl,-Bsymbolic-functions -Wl,-z,relro
-Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr
-Dprivlib=/usr/share/perl/5.20
-Darchlib=/usr/lib/x86_64-linux-gnu/perl/5.20 -Dvendorprefix=/usr
-Dvendorlib=/usr/share/perl5
-Dvendorarch=/usr/lib/x86_64-linux-gnu/perl5/5.20
-Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.20.1
-Dsitearch=/usr/local/lib/x86_64-linux-gnu/perl/5.20.1
-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 -Uversiononly -DDEBUGGING=-g -Doptimize=-O2
-Duseshrplib -Dlibperl=libperl.so.5.20.1 -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv
-fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fwrapv
-fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='4.9.1', 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
/usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed
/usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu
/lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=libc-2.19.so, so=so, useshrplib=true, libperl=libperl.so.5.20
    gnulibc_version='2.19'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib -fstack-protector'

Locally applied patches:
    DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS
default for modules installed from CPAN.
    DEBPKG:debian/db_file_ver - http://bugs.debian.org/340047 Remove
overly restrictive DB_File version check.
    DEBPKG:debian/doc_info - Replace generic man(1) instructions with
Debian-specific information.
    DEBPKG:debian/enc2xs_inc - http://bugs.debian.org/290336 Tweak
enc2xs to follow symlinks and ignore missing @INC directories.
    DEBPKG:debian/errno_ver - http://bugs.debian.org/343351 Remove
Errno version check due to upgrade problems with long-running
processes.
    DEBPKG:debian/libperl_embed_doc - http://bugs.debian.org/186778
Note that libperl-dev package is required for embedded linking
    DEBPKG:fixes/respect_umask - Respect umask during installation
    DEBPKG:debian/writable_site_dirs - Set umask approproately for
site install directories
    DEBPKG:debian/extutils_set_libperl_path - EU:MM: set location of
libperl.a under /usr/lib
    DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or
perllocal.pod for perl or vendor
    DEBPKG:debian/prefix_changes - Fiddle with *PREFIX and variables
written to the makefile
    DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to
the binary targets.
    DEBPKG:debian/instmodsh_doc - Debian policy doesn't install
.packlist files for core or vendor.
    DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH
as per Debian policy.
    DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to
/etc/perl/Net as /usr may not be writable.
    DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
    DEBPKG:debian/module_build_man_extensions -
http://bugs.debian.org/479460 Adjust Module::Build manual page
extensions for the Debian Perl policy
    DEBPKG:debian/prune_libs - http://bugs.debian.org/128355 Prune the
list of libraries wanted to what we actually need.
    DEBPKG:fixes/net_smtp_docs - [rt.cpan.org #36038]
http://bugs.debian.org/100195 Document the Net::SMTP 'Port' option
    DEBPKG:debian/perlivp - http://bugs.debian.org/510895 Make perlivp
skip include directories in /usr/local
    DEBPKG:debian/deprecate-with-apt - http://bugs.debian.org/747628
Point users to Debian packages of deprecated core modules
    DEBPKG:debian/squelch-locale-warnings -
http://bugs.debian.org/508764 Squelch locale warnings in Debian
package maintainer scripts
    DEBPKG:debian/skip-upstream-git-tests - Skip tests specific to the
upstream Git repository
    DEBPKG:debian/patchlevel - http://bugs.debian.org/567489 List
packaged patches for 5.20.1-1 in patchlevel.h
    DEBPKG:debian/skip-kfreebsd-crash - http://bugs.debian.org/628493
[perl #96272] Skip a crashing test case in t/op/threads.t on
GNU/kFreeBSD
    DEBPKG:fixes/document_makemaker_ccflags -
http://bugs.debian.org/628522 [rt.cpan.org #68613] Document that
CCFLAGS should include $Config{ccflags}
    DEBPKG:debian/find_html2text - http://bugs.debian.org/640479
Configure CPAN::Distribution with correct name of html2text
    DEBPKG:debian/perl5db-x-terminal-emulator.patch -
http://bugs.debian.org/668490 Invoke x-terminal-emulator rather than
xterm in perl5db.pl
    DEBPKG:debian/cpan-missing-site-dirs -
http://bugs.debian.org/688842 Fix CPAN::FirstTime defaults with
nonexisting site dirs if a parent is writable
    DEBPKG:fixes/memoize_storable_nstore - [rt.cpan.org #77790]
http://bugs.debian.org/587650 Memoize::Storable: respect 'nstore'
option not respected
    DEBPKG:debian/regen-skip - Skip a regeneration check in unrelated
git repositories
    DEBPKG:fixes/regcomp-mips-optim - [perl #122817]
http://bugs.debian.org/754054 Downgrade the optimization of regcomp.c
on mips and mipsel due to a gcc-4.9 bug
    DEBPKG:debian/makemaker-pasthru - http://bugs.debian.org/758471
Pass LD settings through to subdirectories
    DEBPKG:fixes/perldoc-less-R - [rt.cpan.org #98636]
http://bugs.debian.org/758689 Tell the 'less' pager to allow terminal
escape sequences
    DEBPKG:fixes/hurd_test_todo_socket.t - [perl #122657]
http://bugs.debian.org/758718 Disable failing GNU/Hurd test in
t/io/socket.t
    DEBPKG:fixes/pod_man_reproducible_date -
http://bugs.debian.org/759405 Support POD_MAN_DATE in Pod::Man for the
left-hand footer
    DEBPKG:fixes/data_dump_infinite_recurse - [19be3be] don't recurse
infinitely in Data::Dumper


@INC for perl 5.20.1:
    /etc/perl
    /usr/local/lib/x86_64-linux-gnu/perl/5.20.1
    /usr/local/share/perl/5.20.1
    /usr/lib/x86_64-linux-gnu/perl5/5.20
    /usr/share/perl5
    /usr/lib/x86_64-linux-gnu/perl/5.20
    /usr/share/perl/5.20
    /usr/local/lib/site_perl
    .


Environment for perl 5.20.1:
    HOME=/home/mhorsfall
    LANG=en_US.UTF-8
    LANGUAGE=en_US
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/mhorsfall/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
    PERLDOC=-oman
    PERL_BADLANG (unset)
    SHELL=/bin/bash

@p5pRT
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p5pRT commented Jun 10, 2015

From @Leont

On Wed, Jun 10, 2015 at 5​:07 PM, Matthew Horsfall <perlbug-followup@​perl.org

wrote​:

Perhaps this is expected undesirable behaviour or perhaps this
is a bug. Not sure​:

mhorsfall@​dumai​:~$ perl -e '@​x[$b, $c] =~ "cat"; print 0+@​x, "\n";'
0
mhorsfall@​dumai​:~$ perl -e '@​x[$b, $c] ~~ "cat"; print 0+@​x, "\n";'
Smartmatch is experimental at -e line 1.
1

Smartmatch can do many different things with the left-side argument. Some
of them (such as calling a sub on the right side) require the left-hand
side to be an lvalue. I would classify this as an expected undesirable
behaviour.

Leon

@p5pRT
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p5pRT commented Jun 10, 2015

The RT System itself - Status changed from 'new' to 'open'

@p5pRT
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p5pRT commented Jun 15, 2015

From @rjbs

* Leon Timmermans <fawaka@​gmail.com> [2015-06-10T11​:39​:08]

On Wed, Jun 10, 2015 at 5​:07 PM, Matthew Horsfall <perlbug-followup@​perl.org

wrote​:

Perhaps this is expected undesirable behaviour or perhaps this
is a bug. Not sure​:

mhorsfall@​dumai​:~$ perl -e '@​x[$b, $c] =~ "cat"; print 0+@​x, "\n";'
0
mhorsfall@​dumai​:~$ perl -e '@​x[$b, $c] ~~ "cat"; print 0+@​x, "\n";'
Smartmatch is experimental at -e line 1.
1
Smartmatch can do many different things with the left-side argument. Some
of them (such as calling a sub on the right side) require the left-hand
side to be an lvalue. I would classify this as an expected undesirable
behaviour.

I dunno. This is pretty weird.

What thhe heck is ~~ even doing here? Consider its dispatch. Base on this
example and some others I ran, the slice is dispatched-to like an ARRAY?

But also​:

  ~$ perl -E 'say 1 if %INC{"feature.pm"} ~~ /feat/'
  Smartmatch is experimental at -e line 1.
  Can't modify key/value hash slice in anonymous array ([]) at -e line 1, at EOF
  Execution of -e aborted due to compilation errors.

What a mess.

--
rjbs

@p5pRT
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p5pRT commented Jun 15, 2015

From @ikegami

On Wed, Jun 10, 2015 at 11​:39 AM, Leon Timmermans <fawaka@​gmail.com> wrote​:

On Wed, Jun 10, 2015 at 5​:07 PM, Matthew Horsfall <
perlbug-followup@​perl.org> wrote​:

Perhaps this is expected undesirable behaviour or perhaps this
is a bug. Not sure​:

mhorsfall@​dumai​:~$ perl -e '@​x[$b, $c] =~ "cat"; print 0+@​x, "\n";'
0
mhorsfall@​dumai​:~$ perl -e '@​x[$b, $c] ~~ "cat"; print 0+@​x, "\n";'
Smartmatch is experimental at -e line 1.
1

Smartmatch can do many different things with the left-side argument. Some
of them (such as calling a sub on the right side) require the left-hand
side to be an lvalue. I would classify this as an expected undesirable
behaviour.

Then why is it inconsistent?

$ perl -e '@​x[0] ~~ "cat"; print 0+@​x, "\n";'
Smartmatch is experimental at -e line 1.
1

$ perl -e '$x[0] ~~ "cat"; print 0+@​x, "\n";'
Smartmatch is experimental at -e line 1.
0

@xenu xenu removed the affects-5.20 label Nov 19, 2021
@xenu xenu removed the Severity Low label Dec 29, 2021
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