Re: CGI::Session cannot read data from Data::Dumper

Basically the problem is that Safe creates a new environment and the class into which your data has been blessed is not the same class that exists in our normal environment.

use Safe;
use Devel::Peek;

my $r = 'bless \\ do { my $x = 0 }, "x"';
print Dump(eval $r);
print Dump(Safe->new->reval($r));
print Dump(eval $r);
print Dump(Safe->new->reval($r));
[download]

Which outputs (on my machine at least):

SV = RV(0x1847158) at 0x1830630
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x182fa48
  SV = PVMG(0x18a9974) at 0x182fa48
    REFCNT = 1
    FLAGS = (PADBUSY,PADMY,OBJECT,IOK,pIOK)
    IV = 0
    NV = 0
    PV = 0
    STASH = 0x18d8620   "x"
SV = RV(0x1847188) at 0x18d8b24
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x18d8b00
  SV = PVMG(0x18a8f34) at 0x18d8b00
    REFCNT = 1
    FLAGS = (PADBUSY,PADMY,OBJECT,IOK,pIOK)
    IV = 0
    NV = 0
    PV = 0
    STASH = 0x18d8b54   "x"
SV = RV(0x1847180) at 0x18d88fc
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x18d8920
  SV = PVMG(0x18a90f4) at 0x18d8920
    REFCNT = 1
    FLAGS = (PADBUSY,PADMY,OBJECT,IOK,pIOK)
    IV = 0
    NV = 0
    PV = 0
    STASH = 0x18d8620   "x"
SV = RV(0x1847188) at 0x18d8b18
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x18d8a28
  SV = PVMG(0x18a90f4) at 0x18d8a28
    REFCNT = 1
    FLAGS = (PADBUSY,PADMY,OBJECT,IOK,pIOK)
    IV = 0
    NV = 0
    PV = 0
    STASH = 0x18d8b90   "x"
[download]

Notice how the stash has the same address for both the first and third runs. The second and fourth entries (those that are both from new Safe environments) have stashes where the address does not match either. This is because the x namespace in our environment is not the same as the one in either of the Safe compartments we created. I'm curious which version of CGI::Session you are using since I submitted a crummy fix that walks the structure and reblesses everything in place in the 4.x version (__walk in CGI::Session::Serialize::default).

Comment on Re: CGI::Session cannot read data from Data::Dumper Select or Download Code

Replies are listed 'Best First'.
Re^2: CGI::Session cannot read data from Data::Dumper by lom (Sexton) on Nov 01, 2007 at 11:27 UTC
Thanks a lot for this explanation. I'm using the Debian testing CGI::Session (4.20): # $Id: Session.pm 353 2006-12-05 02:10:19Z markstos $ $CGI::Session::VERSION = '4.20'; __xwalk is definitely present.	[reply]
Re^3: CGI::Session cannot read data from Data::Dumper by !1 (Hermit) on Nov 01, 2007 at 13:21 UTC
If you don't mind, could you tell me what this returns? `use Safe; use Devel::Peek; my $x = bless \ do { my $a = 0 }, "x"; print Dump($x); my $y = Safe->new->reval('bless \\ do { my $a = 0 }, "x"'); print Dump($y); bless $y, ref $y; print Dump($y);` [download]	[reply] [d/l]
Re^4: CGI::Session cannot read data from Data::Dumper by lom (Sexton) on Nov 02, 2007 at 08:32 UTC
here you are: SV = RV(0x81786c0) at 0x8151690 REFCNT = 1 FLAGS = (PADBUSY,PADMY,ROK) RV = 0x815163c SV = PVMG(0x81d1948) at 0x815163c REFCNT = 2 FLAGS = (PADBUSY,PADMY,OBJECT,IOK,pIOK) IV = 0 NV = 0 PV = 0 STASH = 0x8150b44 "x" SV = RV(0x81786f4) at 0x8151624 REFCNT = 1 FLAGS = (PADBUSY,PADMY,ROK) RV = 0x81fbd04 SV = PVMG(0x81d1b28) at 0x81fbd04 REFCNT = 1 FLAGS = (PADBUSY,PADMY,OBJECT,IOK,pIOK) IV = 0 NV = 0 PV = 0 STASH = 0x81fbd58 "x" SV = RV(0x81786f4) at 0x8151624 REFCNT = 1 FLAGS = (PADBUSY,PADMY,ROK) RV = 0x81fbd04 SV = PVMG(0x81d1b28) at 0x81fbd04 REFCNT = 1 FLAGS = (PADBUSY,PADMY,OBJECT,IOK,pIOK) IV = 0 NV = 0 PV = 0 STASH = 0x8150b44 "x" [download]	[reply] [d/l]


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