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
  .

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)
#####

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

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.

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