Name
SPVM::Document::Language::GarbageCollection - Garbage Collection in SPVM Language
Description
This document describes garbage collection in SPVM language.
Garbage Collection
Reference Count GC
Garbage collection in SPVM is a reference counted GC.
The object is destroyed when its reference count reaches 0.
The reference count of an object assigned by the assignment operator is incremented by 1.
# The reference count is incremented by 1
my $object = Point->new;The reference count of an object whose assignment is removed by an assignment operator is decreased by 1.
# The reference count is decremented by 1
$object = undef;Reference counts incremented by assignments to local variables are decremented at the end of its scope.
{
# The reference count is incremented by 1
my $object = Point->new;
# The reference count of $object is decremented by 1 at the end of this scope
}Weak Reference
SPVM supports weak references. Weak references are used to avoid circular references.
This is an example that objects have circular references.
{
my $foo = new Foo;
my $bar = new Bar;
$foo->{bar} = $bar;
$bar->{foo} = $foo;
}The weaken operator converts a reference to a weak reference.
{
my $foo = new Foo;
my $bar = new Bar;
$foo->{bar} = $bar;
$bar->{foo} = $foo;
weaken $foo->{bar};
}If a reference is convertd to a weak reference, the reference count of the referenced object is decremented by 1.
And the weaken flag of the field trun on, and the back reference from the field is added to the referenced object.
The isweak operator checks if the weaken flag of the field turn on.
my $isweak = isweaken $foo->{bar};The unweaken operator converts a weak reference to a reference.
unweaken $foo->{bar};If a weak reference is convertd to a reference, the reference count of the referenced object is incremented by 1.
And the weaken flag of the field trun off, and the back reference from the field is removed from the referenced object.
Copyright & License
Copyright (c) 2023 Yuki Kimoto
MIT License