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NEXT::DISTINCT can wrongly skip parent function calls #13248

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p5pRT opened this issue Sep 11, 2013 · 6 comments
Closed

NEXT::DISTINCT can wrongly skip parent function calls #13248

p5pRT opened this issue Sep 11, 2013 · 6 comments
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@p5pRT
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@p5pRT p5pRT commented Sep 11, 2013

Migrated from rt.perl.org#119731 (status was 'rejected')

Searchable as RT119731$

@p5pRT
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@p5pRT p5pRT commented Sep 11, 2013

From ryan.delany@oracle.com

NEXT​::DISTINCT can wrongly skip parent function calls when an object

is created at the same memory address as an old object. NEXT uses

the memory reference as part of a key into the $NEXT​::SEEN hash, so

if the old object with the same memory reference is already in the

$NEXT​::SEEN hash, NEXT​::DISTINCT will think that the function call

has already been seen and it will skip it.

This can result in an object that did not call its parent init function,

if they are using NEXT​::DISTINCT​::_init().

This only happens when the $NEXT​::SEEN variable exists already in the scope

when calling NEXT​::DISTINCT​::_init(). This can happen when you have two

inheritence trees and one calls the other. I have reproduced this with perl

version 5.10.1 on Linux and with perl version 5.18.1 on Windows.

The attached reproducer.pl will reproduce the problem. The second time a "Foo" object

is created, its parent's _init() will be skipped. It does this because it is created at the same

memory location as a previous object, so NEXT thinks it has already seen the function call

to its parent.

Output from attached reproducer.pl is below.

(notice how the second object does not have the 'parent' instance variable)

ref​: Foo=HASH(0x2578990)

$VAR1 = bless( {

  'parent' => 1

  }, 'Foo' );

ref​: Foo=HASH(0x2578990)

$VAR1 = bless( {}, 'Foo' );

One way to fix the issue would be to assign a unique identifier for

the object in the NEXT code, since the memory reference is not always unique.

I was able to implement a fix using FieldHash, but there are other ways

to fix it as well. Another idea would be to make sure an object is cleared

from the $NEXT​::SEEN hash when it is destroyed or cleaned up.

I have attached a patch file of my changes.


Flags​:

  category=library

  severity=low

  module=NEXT


Site configuration information for perl 5.18.1​:

Configured by strawberry-perl at Tue Aug 13 17​:19​:29 2013.

Summary of my perl5 (revision 5 version 18 subversion 1) configuration​:

 

  Platform​:

  osname=MSWin32, osvers=4.0, archname=MSWin32-x64-multi-thread

  uname='Win32 strawberry-perl 5.18.1.1 #1 Tue Aug 13 17​:18​:28 2013 x64'

  config_args='undef'

  hint=recommended, useposix=true, d_sigaction=undef

  useithreads=define, usemultiplicity=define

  useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef

  use64bitint=define, use64bitall=undef, uselongdouble=undef

  usemymalloc=n, bincompat5005=undef

  Compiler​:

  cc='gcc', ccflags =' -s -O2 -DWIN32 -DWIN64 -DCONSERVATIVE -DPERL_TEXTMODE_SCRIPTS -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DUSE_PERLIO -fno-strict-aliasing -mms-bitfields',

  optimize='-s -O2',

  cppflags='-DWIN32'

  ccversion='', gccversion='4.7.3', gccosandvers=''

  intsize=4, longsize=4, ptrsize=8, doublesize=8, byteorder=12345678

  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12

  ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='long long', lseeksize=8

  alignbytes=8, prototype=define

  Linker and Libraries​:

  ld='g++', ldflags ='-s -L"C​:\strawberry\perl\lib\CORE" -L"C​:\strawberry\c\lib"'

  libpth=C​:\strawberry\c\lib C​:\strawberry\c\x86_64-w64-mingw32\lib

  libs=-lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32

  perllibs=-lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32

  libc=, so=dll, useshrplib=true, libperl=libperl518.a

  gnulibc_version=''

  Dynamic Linking​:

  dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '

  cccdlflags=' ', lddlflags='-mdll -s -L"C​:\strawberry\perl\lib\CORE" -L"C​:\strawberry\c\lib"'

Locally applied patches​:

 


@​INC for perl 5.18.1​:

  C​:/strawberry/perl/site/lib

  C​:/strawberry/perl/vendor/lib

  C​:/strawberry/perl/lib

  .


Environment for perl 5.18.1​:

  HOME (unset)

  LANG (unset)

  LANGUAGE (unset)

  LD_LIBRARY_PATH (unset)

  LOGDIR (unset)

  PATH=C​:\Windows\system32;C​:\Windows;C​:\Windows\System32\Wbem;C​:\Windows\System32\WindowsPowerShell\v1.0\;C​:\Windows\Program Files\Microsoft Office\Office14;C​:\Program Files (x86)\Windows Imaging\;C​:\Program Files (x86)\Enterprise Vault\EVClient\;C​:\strawberry\c\bin;C​:\strawberry\perl\site\bin;C​:\strawberry\perl\bin

  PERL_BADLANG (unset)

  SHELL (unset)

@p5pRT
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@p5pRT p5pRT commented Sep 11, 2013

@p5pRT
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@p5pRT p5pRT commented Sep 11, 2013

From ryan.delany@oracle.com

NEXT-distinct.patch
--- /usr/share/perl5/NEXT.pm    2013-04-30 08:49:01.000000000 -0400
+++ NEXT2.pm    2013-08-29 10:42:17.102001474 -0400
@@ -1,9 +1,13 @@
 package NEXT;
 $VERSION = '0.64';
 use Carp;
+use Hash::Util::FieldHash qw(fieldhashes);
 use strict;
 use overload ();

+fieldhashes \my(%IDs);
+my $Last_ID = 0;
+
 sub NEXT::ELSEWHERE::ancestors
 {
        my @inlist = shift;
@@ -50,6 +54,12 @@
         my $key = ref $self && overload::Overloaded($self)
             ? overload::StrVal($self) : $self;

+        if (exists $IDs{$key}) {
+            $key = $IDs{$key};
+        } else {
+            $key = ++$Last_ID;
+        }
+
         local ($NEXT::NEXT{$key,$wanted_method}, $NEXT::SEEN) =
             ($NEXT::NEXT{$key,$wanted_method}, $NEXT::SEEN);
@p5pRT
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@p5pRT p5pRT commented Sep 12, 2013

From @jkeenan

According to Porting/Maintainers.pl, the NEXT distribution is maintained
on CPAN. Accordingly, I have moved this report into that distro's bug
queue at​:

https://rt.cpan.org/Ticket/Display.html?id=88620

Thank you very much.
Jim Keenan

@p5pRT
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@p5pRT p5pRT commented Sep 12, 2013

From [Unknown Contact. See original ticket]

According to Porting/Maintainers.pl, the NEXT distribution is maintained
on CPAN. Accordingly, I have moved this report into that distro's bug
queue at​:

https://rt.cpan.org/Ticket/Display.html?id=88620

Thank you very much.
Jim Keenan

@p5pRT
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@p5pRT p5pRT commented Sep 12, 2013

@jkeenan - Status changed from 'new' to 'rejected'

@p5pRT p5pRT closed this Sep 12, 2013
@p5pRT p5pRT added the Severity Low label Oct 19, 2019
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