Re: Readonly problems (Devel::Peek, Scalar::Util::readonly bug)

hash keys are read-only but they're not really readonly ... so Scalar::Util::readonly has bug in that it doesn't document the nuances of readonlyness :)

#!/usr/bin/perl --
use strict; use warnings;
use Devel::Peek qw/ Dump /;
use Readonly;
Readonly::Scalar my $rs => 66;
my %hh = qw/ A B /;
while( my( $k, $v ) = each %hh ){
    Dump( $k );
    Dump( $v );
}
for( 1 ){
    Dump( $_ ); ## the readonliest
}
Dump( $rs );
__END__
[download]

SV = PV(0x3f7b44) at 0x99b8ac
  REFCNT = 1
  FLAGS = (PADMY,POK,FAKE,READONLY,pPOK)
  PV = 0x99ce88 "A"
  CUR = 1
  LEN = 0
SV = PV(0x3f7b4c) at 0xaca8bc
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK)
  PV = 0xadf504 "B"\0
  CUR = 1
  LEN = 12
SV = IV(0xae0670) at 0xae0674
  REFCNT = 2
  FLAGS = (PADTMP,IOK,READONLY,pIOK)
  IV = 1
SV = PVMG(0xad50e4) at 0x3f9bac
  REFCNT = 1
  FLAGS = (PADMY,GMG,SMG,RMG)
  IV = 0
  NV = 0
  PV = 0
  MAGIC = 0x99402c
    MG_VIRTUAL = &PL_vtbl_packelem
    MG_TYPE = PERL_MAGIC_tiedscalar(q)
    MG_FLAGS = 0x02
      REFCOUNTED
    MG_OBJ = 0x3f9adc
    SV = IV(0x3f9ad8) at 0x3f9adc
      REFCNT = 1
      FLAGS = (ROK)
      RV = 0xad353c
      SV = PVMG(0xad50c4) at 0xad353c
        REFCNT = 1
        FLAGS = (PADMY,OBJECT,IOK,pIOK)
        IV = 66
        NV = 0
        PV = 0
        STASH = 0xacab0c        "Readonly::Scalar"

Oh, and http://perldoc.perl.org/perlapi.html#sv_magic is unreadable ...

http://search.cpan.org/dist/illguts/index.html, redefining Internals::SvREADONLY

Comment on Re: Readonly problems (Devel::Peek, Scalar::Util::readonly bug) Download Code

Replies are listed 'Best First'.
Re^2: Readonly problems ( Scalar::Readonly::readonly ) by Anonymous Monk on Dec 17, 2013 at 01:35 UTC
?node_id=3989;HIT=readonly;re=N Just what is 'readonly' in Perl and Perl 6? Readonly variable Module Readonly What is the difference between the constant construct in Perl and the Readonly construct in Perl? Reliability of SvREADONLY Faster way to readonly are Attribute::Constant, Data::Lock, Scalar::Readonly, `use Scalar::Readonly qw/ readonly_on /; use Devel::Peek qw/ Dump /; my $f=66; readonly_on($f); Dump($f); __END__ SV = IV(0x99ba38) at 0x99ba3c REFCNT = 1 FLAGS = (PADMY,IOK,READONLY,pIOK) IV = 66` [download] Scalar::Readonly::readonly also simply checks for SvREADONLY flag, and no others (no FAKE), so it'll be a false positive on HASH keys	[reply] [d/l]
Re^3: Readonly problems ( Scalar::Readonly::readonly ) by runrig (Abbot) on Dec 17, 2013 at 01:47 UTC
Thanks, I don't really want to use readonly() though, I was just tracking down a bug involving DBI/DBD::Oracle. I tracked it down to code that went something like: `my $data = {}; my $sth = $dbh->prepare($sql); $sth->bind_param_inout(':foo' => \$data->{foo}, 10); while ( my ($k, $v) = each %hash ) { $data->{foo} = $k; $sth->execute(); }` [download] And I got a 'modification of readonly value' error on the execute. Workaround is to modify the 'readonly' value before the execute with something like: `$k .= '';` [download] Update: And for now, that whole thing needs a reset every few iterations, as execute() leaks memory with inout parameters. Update2: And the previously mentioned 'leak' has been fixed in the latest release.	[reply] [d/l] [select]
Re^4: Readonly problems ( Scalar::Readonly::readonly ) by choroba (Cardinal) on Dec 17, 2013 at 14:53 UTC
Would the following also work? `$data->{foo} = "$k";` [download] لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l]
Re^5: Readonly problems ( Scalar::Readonly::readonly ) by runrig (Abbot) on Dec 17, 2013 at 16:47 UTC
Re^6: Readonly problems ( Scalar::Readonly::readonly ) by choroba (Cardinal) on Dec 17, 2013 at 17:08 UTC


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