On Jan 19, 2007, at 12:55 PM, Richard Jones wrote:
while ( my $ref = $sth->fetchrow_arrayref() ) { # $ref is arrayref
push @$ref, 1; # line xx
}
dies with 'Modification of read-only value attempted at .. line xx'
I can't see the difference here between the two $ref arrayrefs, but
Perl obviously can. Unfortunately 'use diagnostics' didn't help as
I think I must be missing something obvious.
Yes, that reference has a flag READONLY turned on, this is a dump of
an example I ran to figure this out (attached below):
SV = RV(0x1823abc) at 0x1856984
REFCNT = 1
FLAGS = (TEMP,ROK)
RV = 0x1856894
SV = PVAV(0x185848c) at 0x1856894
REFCNT = 2
FLAGS = (READONLY) <-- look here
IV = 0
NV = 0
ARRAY = 0x4d80b0
FILL = 0
MAX = 3
ARYLEN = 0x0
FLAGS = (REAL)
Elt No. 0
SV = NV(0x1813c00) at 0x1856978
REFCNT = 1
FLAGS = (NOK,pNOK)
NV = 1
There are several lines in
http://search.cpan.org/src/TIMB/DBI-1.53/DBI.xs
with this code:
SvREADONLY_on(av);
So the answer is that you get a regular arrayref with that flag
turned on by hand from XS code. That's why it is read-only.
-- fxn
use DBI;
use strict;
use warnings;
use Devel::Peek;
my $dbh = DBI->connect("dbi:SQLite:dbname=foo.db");
$dbh->do("drop table if exists foos");
$dbh->do("create table foos (id integer)");
$dbh->do("insert into foos (id) values (1)");
my $sth = $dbh->prepare("select id from foos");
$sth->execute;
Dump $sth->fetchrow_arrayref;
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