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Malfunction of delete @x[@y] when @x and @y are identical #13742

Open p5pRT opened 10 years ago

p5pRT commented 10 years ago

Migrated from rt.perl.org#121677 (status was 'open')

Searchable as RT121677$

p5pRT commented 10 years ago

From anno5@me.com

I noticed that "delete @​x[@​y]" can go wrong in the special case when @​x and @​y are identical. Example​:

  use warnings;   my @​array = (2\, 1\, 2);   delete @​array[@​array]; # deleting from itself   say "(@​array)";

The response is Use of uninitialized value in delete at ./ttt line 11. ()

The warning is unexpected and the resulting array ought to still have 2 on index position 0. Indeed\, "delete @​array[my @​dup = @​array]" shows the expected behavior. Apparently the special case of identical @​x and @​y needs more attention than it gets.

Regards\, Anno

Summary of my perl5 (revision 5 version 18 subversion 2) configuration​:  
  Platform​:   osname=darwin\, osvers=13.1.0\, archname=darwin-multi-2level   uname='darwin radom 13.1.0 darwin kernel version 13.1.0​: thu jan 16 19​:40​:37 pst 2014; root​:xnu-2422.90.20~2release_x86_64 x86_64 '   config_args='-des -Duseshrplib -Dusemultiplicity'   hint=recommended\, useposix=true\, d_sigaction=define   useithreads=undef\, 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 ='-fno-common -DPERL_DARWIN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -I/opt/local/include'\,   optimize='-O3'\,   cppflags='-fno-common -DPERL_DARWIN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -I/opt/local/include'   ccversion=''\, gccversion='4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.38)'\, 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='env MACOSX_DEPLOYMENT_TARGET=10.3 cc'\, ldflags =' -fstack-protector -L/usr/local/lib -L/opt/local/lib'   libpth=/usr/local/lib /opt/local/lib /usr/lib   libs=-lgdbm -ldbm -ldl -lm -lutil -lc   perllibs=-ldl -lm -lutil -lc   libc=\, so=dylib\, useshrplib=true\, libperl=libperl.dylib   gnulibc_version=''   Dynamic Linking​:   dlsrc=dl_dlopen.xs\, dlext=bundle\, d_dlsymun=undef\, ccdlflags=' '   cccdlflags=' '\, lddlflags=' -bundle -undefined dynamic_lookup -L/usr/local/lib -L/opt/local/lib -fstack-protector'

Characteristics of this binary (from libperl)​:   Compile-time options​: HAS_TIMES MULTIPLICITY PERLIO_LAYERS   PERL_DONT_CREATE_GVSV   PERL_HASH_FUNC_ONE_AT_A_TIME_HARD   PERL_IMPLICIT_CONTEXT PERL_MALLOC_WRAP   PERL_PRESERVE_IVUV PERL_SAWAMPERSAND USE_64_BIT_ALL   USE_64_BIT_INT USE_LARGE_FILES USE_LOCALE   USE_LOCALE_COLLATE USE_LOCALE_CTYPE   USE_LOCALE_NUMERIC USE_PERLIO USE_PERL_ATOF   Built under darwin   Compiled at Mar 17 2014 21​:11​:28   %ENV​:   PERL5LIB="/Users/anno/lib/perl5"   PERLBREW_BASHRC_VERSION="0.42"   PERLBREW_HOME="/Users/anno/.perlbrew"   PERLBREW_MANPATH=""   PERLBREW_PATH="/Users/anno/perl5/perlbrew/bin"   PERLBREW_ROOT="/Users/anno/perl5/perlbrew"   PERLBREW_VERSION="0.67"   PERL_UNICODE="SALAD"   @​INC​:   /Users/anno/lib/perl5   /usr/local/lib/perl5/site_perl/5.18.2/darwin-multi-2level   /usr/local/lib/perl5/site_perl/5.18.2   /usr/local/lib/perl5/5.18.2/darwin-multi-2level   /usr/local/lib/perl5/5.18.2   /usr/local/lib/perl5/site_perl/5.18.1/darwin-multi-2level   /usr/local/lib/perl5/site_perl/5.18.1   /usr/local/lib/perl5/site_perl/5.18.0/darwin-multi-2level   /usr/local/lib/perl5/site_perl/5.18.0   /usr/local/lib/perl5/site_perl/5.16.1   /usr/local/lib/perl5/site_perl/5.16.0   /usr/local/lib/perl5/site_perl/5.14.2   /usr/local/lib/perl5/site_perl/5.14.1   /usr/local/lib/perl5/site_perl/5.14.0   /usr/local/lib/perl5/site_perl/5.12.3   /usr/local/lib/perl5/site_perl/5.12.1   /usr/local/lib/perl5/site_perl/5.12.0   /usr/local/lib/perl5/site_perl/5.10.1   /usr/local/lib/perl5/site_perl   .

p5pRT commented 10 years ago

From @jkeenan

On Thu Apr 17 09​:32​:26 2014\, anno5@​me.com wrote​:

I noticed that "delete @​x[@​y]" can go wrong in the special case when @​x and @​y are identical. Example​:

use warnings; my @​array = (2\, 1\, 2); delete @​array[@​array]; # deleting from itself say "(@​array)";

The response is Use of uninitialized value in delete at ./ttt line 11. ()

The warning is unexpected and the resulting array ought to still have 2 on index position 0. Indeed\, "delete @​array[my @​dup = @​array]" shows the expected behavior.

I think this also is the expected behavior​:

##### my @​array = (2\, 1\, 2); my @​second_array = (2\, 1\, 2); delete @​array[@​second_array]; say "(@​array)"; ##### Output​: (2) #####

p5pRT commented 10 years ago

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

p5pRT commented 10 years ago

From @jkeenan

On Thu Apr 17 09​:32​:26 2014\, anno5@​me.com wrote​:

I noticed that "delete @​x[@​y]" can go wrong in the special case when @​x and @​y are identical. Example​:

use warnings; my @​array = (2\, 1\, 2); delete @​array[@​array]; # deleting from itself say "(@​array)";

The response is Use of uninitialized value in delete at ./ttt line 11. ()

The warning is unexpected and the resulting array ought to still have 2 on index position 0. Indeed\, "delete @​array[my @​dup = @​array]" shows the expected behavior. Apparently the special case of identical @​x and @​y needs more attention than it gets.

Regards\, Anno

On the other hand\, 'perldoc -f delete' says​:

##### WARNING​: Calling delete on array values is deprecated and likely to be removed in a future version of Perl. ##### So maybe we shouldn't worry about this too much.

p5pRT commented 10 years ago

From @abigail

On Thu\, Jul 03\, 2014 at 06​:18​:54PM -0700\, James E Keenan via RT wrote​:

On Thu Apr 17 09​:32​:26 2014\, anno5@​me.com wrote​:

I noticed that "delete @​x[@​y]" can go wrong in the special case when @​x and @​y are identical. Example​:

use warnings; my @​array = (2\, 1\, 2); delete @​array[@​array]; # deleting from itself say "(@​array)";

The response is Use of uninitialized value in delete at ./ttt line 11. ()

The warning is unexpected and the resulting array ought to still have 2 on index position 0. Indeed\, "delete @​array[my @​dup = @​array]" shows the expected behavior. Apparently the special case of identical @​x and @​y needs more attention than it gets.

Regards\, Anno

On the other hand\, 'perldoc -f delete' says​:

##### WARNING​: Calling delete on array values is deprecated and likely to be removed in a future version of Perl. ##### So maybe we shouldn't worry about this too much.

Perhaps.

But then\, IMO\, it should actually be removed\, instead of lingering around.

Abigail