| Subject: | Tied arrays and hashes can fail when not initialized and a stability modification |
| From: | CHOLT [...] cpan.org |
If you tie a hash or array, but never insert anything into either before accessing them, you can get a failure on accessing them because the internal {_data} value has not been predeclared to be an empty hash or array.
Also If you perform thaw operations in an eval statement, you can safely read values without locking the variable each time. You then only need to lock on write.
Here is some patch text -->
--- Shareable.pm.1 2012-10-12 19:35:32.000000000 -0600
+++ Shareable.pm 2017-04-06 10:26:24.000000000 -0600
@@ -315,7 +315,8 @@
my $key = shift;
$self->{_data} = _thaw($self->{_shm}) unless $self->{_lock};
- return exists $self->{_data}->{$key};
+ return (ref($self->{_data}) eq 'ARRAY') ?
+ exists($self->{_data}->[$key]) : exists($self->{_data}->{$key});
}
sub FIRSTKEY {
@@ -543,7 +544,23 @@
my $tag = substr $ice, 0, 14, '';
if ($tag eq 'IPC::Shareable') {
- my $water = thaw $ice;
+ my $water;
+ eval '$water = thaw $ice;';
+
+ #thaw failed for some reason
+ if($@){
+ if($@ =~ /corrupt|binary/i){ #perhaps storable string is partial
+ my $time = time();
+ while(abs(time() - $time) < 5){
+ sleep 1;
+ $ice = $s->shmread;
+ eval '$water = thaw $ice;';
+ last if(!$@);
+ }
+ }
+ die $@ if($@);
+ }
+
defined($water) or do {
require Carp;
Carp::croak "Munged shared memory segment (size exceeded?)";
@@ -592,7 +609,16 @@
_type => $type,
_was_changed => 0,
};
- $sh->{_data} = _thaw($s),
+ $sh->{_data} = _thaw($s);
+
+ #fix for uninitialized shared memory and complex datatypes
+ if($type ne 'SCALAR' && !defined($sh->{_data})){
+ $sh->{_data} = ($type eq 'ARRAY') ? [] : {};
+ defined _freeze($sh->{_shm} => $sh->{_data}) or do {
+ require Carp;
+ Carp::croak "Could not write to shared memory: $!\n";
+ };
+ }
my $there = $sem->getval(SEM_MARKER);
if ($there == SHM_EXISTS) {