From mjtg@cus.cam.ac.uk

*********************
#!/usr/local/bin/perl -w

use strict;

package X;

sub new {
  my $class = shift;

  my $obj = {
  X => 1,
  Y => 2,
  EQN => '$x * $y * $t',
  };
  return bless $obj, $class;
}

{
  my ($x, $y);
  sub calculate {
  my $obj = shift;

  unless (defined $x) { # <---- AAA
  $x = $obj->{X}; # <---- BBB
  $y = $obj->{Y};
  }

  my $t = shift;

# print "$x $y\n";

  my $z = eval $obj->{EQN};
  return $z;
  }
}

package main;

my $x = new X;
my $z = $x->calculate(3);

print "Z is $z.\n";
***********************

Now, running the above program generates the following​:

Use of uninitialized value at (eval 1) line 1.
Use of uninitialized value at (eval 1) line 1.
Z is 0.

Bug shows in both 5.005_03 and 5.0065_62.

Running under the debugger, we see at points AAA and BBB that $x and $y
refer to different variables​:

X​::calculate(-​:21)​: unless (defined $x) {
  DB<1> x \$x, \$y
0 SCALAR(0x1aba98)
  -> undef
1 SCALAR(0x1cbc50)
  -> undef
  DB<2> s
X​::calculate(-​:22)​: $x = $obj->{X};
  DB<2> x \$x, \$y
0 SCALAR(0xdd678)
  -> undef
1 SCALAR(0xdd690)
  -> undef
  DB<3>

So the binding of lexicals has got confused in some way.

Mike Guy

% ./perl -V
Summary of my perl5 (revision 5.0 version 5 subversion 62) configuration​:
  Platform​:
  osname=sunos, osvers=4.1.3, archname=sun4-sunos
  uname='sunos nmg1.csi. 4.1.3 1 sun4c '
  config_args='-Doptimise=-O -Uusethreads -des'
  hint=previous, useposix=true, d_sigaction=define
  usethreads=undef useperlio=undef d_sfio=undef
  use64bits=undef usemultiplicity=undef
  Compiler​:
  cc='gcc', optimize='-O', gccversion=2.7.2.3
  cppflags='-I/usr/local/include'
  ccflags ='-I/usr/local/include'
  stdchar='unsigned char', d_stdstdio=define, usevfork=true
  intsize=4, longsize=4, ptrsize=4, doublesize=8
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=8
  alignbytes=8, usemymalloc=y, prototype=define
  Linker and Libraries​:
  ld='ld', ldflags =' -L/usr/local/lib'
  libpth=/usr/local/lib /lib /usr/lib /usr/ucblib
  libs=-ldbm -ldl -lm -lc -lposix
  libc=/lib/libc.so.1.8, so=so, useshrplib=false, libperl=libperl.a
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags=' '
  cccdlflags='-fpic', lddlflags='-assert nodefinitions -L/usr/local/lib'

Characteristics of this binary (from libperl)​:
  Locally applied patches​:
  perldoc.temp
  install.w
  Built under sunos
  Compiled at Oct 27 1999 01​:31​:39
  @​INC​:
  /home/mjtg/perl5.005_62a/lib
  /home/mjtg/perl5.005_62a/lib
  /home/mjtg/perl5.005_62a/lib/site_perl
  .

From [Unknown Contact. See original ticket]

This seems to still be an issue @​8101.

-spp

Ala Qumsieh <aqumsieh@​matrox.com> reports in c.l.p.misc that the
following program gives incorrect output​:

*********************
#!/usr/local/bin/perl -w

use strict;

package X;

sub new {
  my $class = shift;

  my $obj = {
  X => 1,
  Y => 2,
  EQN => '$x * $y * $t',
  };
  return bless $obj, $class;
}

{
  my ($x, $y);
  sub calculate {
  my $obj = shift;

  unless (defined $x) { # <---- AAA
  $x = $obj->{X}; # <---- BBB
  $y = $obj->{Y};
  }

  my $t = shift;

# print "$x $y\n";

  my $z = eval $obj->{EQN};
  return $z;
  }
}

package main;

my $x = new X;
my $z = $x->calculate(3);

print "Z is $z.\n";
***********************

Now, running the above program generates the following​:

Use of uninitialized value at (eval 1) line 1.
Use of uninitialized value at (eval 1) line 1.
Z is 0.

Bug shows in both 5.005_03 and 5.0065_62.

Running under the debugger, we see at points AAA and BBB that $x and $y
refer to different variables​:

X​::calculate(-​:21)​: unless (defined $x) {
  DB<1> x \$x, \$y
0 SCALAR(0x1aba98)
  -> undef
1 SCALAR(0x1cbc50)
  -> undef
  DB<2> s
X​::calculate(-​:22)​: $x = $obj->{X};
  DB<2> x \$x, \$y
0 SCALAR(0xdd678)
  -> undef
1 SCALAR(0xdd690)
  -> undef
  DB<3>

So the binding of lexicals has got confused in some way.

Mike Guy

From The RT System itself

$ ./perl -w -Ilib ../t.pl
Use of uninitialized value in multiplication (*) at (eval 1) line 1.
Use of uninitialized value in multiplication (*) at (eval 1) line 1.
Z is 0.

From The RT System itself

use strict;
use warnings;

package X;

sub new {
  my $class = shift;

  my $obj = {
  X => 1,
  Y => 2,
  EQN => '$x * $y * $t',
  };
  return bless $obj, $class;
}

{
  my ($x, $y);
  sub calculate {
  my $obj = shift;

  unless (defined $x) { # <---- AAA
  $x = $obj->{X}; # <---- BBB
  $y = $obj->{Y};
  }

  my $t = shift;

# print "$x $y\n";

  my $z = eval $obj->{EQN};
  return $z;
  }
}

package main;

my $x = new X;
my $z = $x->calculate(3);

print "Z is $z.\n";

From @gbarr

This is still present in 5.8.0

From @iabyn

Fixed by patch #18223 in bleedperl.

@iabyn - Status changed from 'open' to 'resolved'