p5pRT
commented
9 years ago From mark@markandruth.co.uk
Created by mark@markandruth.co.uk
This is a bug report for perl from mark@markandruth.co.uk\, generated with the help of perlbug 1.39 running under perl 5.18.2.
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A simple script like:
use threads; use Devel::Peek; use threads::shared; my $var = { a => 0.1 + 0 }; Dump($var); my $t = shared_clone $var; Dump( $t->{a} ); my $v = $t->{a}; my %v = %$t; Dump($v); Dump($v{a});
Produces somewhat incorrect output on the first Dump statement compared to the second two (see below). This shows that dereferencing a shared_clone hash value directly does not produce the same information as copying it to a variable in the local thread. I found this issue using MongoDB as we wanted to store a double datatype\, however when dereferencing straight from a shared variable it was inserting a string.
A solution is to clone (using pure-perl) into the local thread using a function like:
sub _fix_dequeue { my ( $v ) = @_;
my $ref = ref $v or return $v;
my $ret; if ( $ref eq 'ARRAY' ) { $ret = [ map { _fix_dequeue( $_ ) } @$v ]; } elsif ( $ref eq 'HASH' ) { $ret = { map { $_ => _fix_dequeue( $v->{$_} ) } keys %$v }; }
return $ret; }
Here is the output of the first program on my computer showing the dereference compared to copying to local thread produces different results for a SvNV type.
SV = IV(0x1311bb0) at 0x1311bc0 REFCNT = 1 FLAGS = (PADMY\,ROK) RV = 0x12e9cb8 SV = PVHV(0x12f09b0) at 0x12e9cb8 REFCNT = 1 FLAGS = (SHAREKEYS) ARRAY = 0x131a920 (0:7\, 1:1) hash quality = 100.0% KEYS = 1 FILL = 1 MAX = 7 Elt "a" HASH = 0x1bb2e90c SV = NV(0x13283e8) at 0x12e9e98 REFCNT = 1 FLAGS = (NOK\,pNOK) NV = 0.1 SV = PVLV(0xaf5010) at 0xa82e98 REFCNT = 1 FLAGS = (TEMP\,GMG\,SMG\,RMG) IV = 0 NV = 0 PV = 0 MAGIC = 0xaa3df0 MG_VIRTUAL = 0x7fb7749412e0 MG_TYPE = PERL_MAGIC_tiedelem(p) MG_FLAGS = 0x12 REFCOUNTED DUP MG_OBJ = 0xaa08e0 SV = IV(0xaa08d0) at 0xaa08e0 REFCNT = 2 FLAGS = (ROK) RV = 0xaa0958 SV = PVMG(0xb69ed0) at 0xaa0958 REFCNT = 1 FLAGS = (OBJECT\,IOK\,pIOK) IV = 12141928 NV = 0 PV = 0 STASH = 0xb73130 "threads::shared::tie" MG_LEN = -2 MG_PTR = 0xa82cb8 => HEf_SVKEY SV = PV(0xa83ba0) at 0xa82cb8 REFCNT = 2 FLAGS = (POK\,pPOK) PV = 0xa882e0 "a"\0 CUR = 1 LEN = 16 TYPE = T TARGOFF = 0 TARGLEN = 0 TARG = 0xafd5d0 FLAGS = 0 SV = PVNV(0xb3fe00) at 0xb8b9a0 REFCNT = 1 FLAGS = (PADMY\,NOK\,pNOK) IV = 0 NV = 0.1 PV = 0 SV = PVMG(0xb69f30) at 0xba5f00 REFCNT = 1 FLAGS = (NOK\,pNOK) IV = 0 NV = 0.1 PV = 0
Migrated from rt.perl.org#125778 (status was 'open')
Searchable as RT125778$