Bug #13498
closedWeakref, Weakmap and define_finalizer don't work on frozen objects
Description
I'm just creating a single ticket for these issues, I guess they're actually all the same (I've seen weakref uses weakmap, not sure about define_finalizer).
require 'weakref'
map = ObjectSpace::WeakMap.new
o = Object.new
o.freeze
begin
WeakRef.new(o)
rescue => e
STDERR.puts e
end
begin
map[o] = 'foo'
rescue => e
STDERR.puts e
end
begin
map['bar'] = o
rescue => e
STDERR.puts e
end
begin
ObjectSpace.define_finalizer(o, ->(id) { p id })
rescue => e
STDERR.puts e
end
Every statement here raises the runtime error "can't modify frozen Object". The documentation doesn't mention that frozen objects are not allowed, the closest reference we get is a short paragraph in WeakRef: "With this you will have to limit your self to String keys, otherwise you will get an ArgumentError because WeakRef cannot create a finalizer for a Symbol. Symbols are immutable and cannot be garbage collected"
Updated by nobu (Nobuyoshi Nakada) over 7 years ago
- Status changed from Open to Assigned
- Assignee set to nobu (Nobuyoshi Nakada)
Weakref is implemented by finalizer to notify that an object is collected, and you can't define finalizers on frozen objects.
Probably we need to move finalizer flags to a separate region (like bitmap marking).
Updated by RubyBugs (A Nonymous) about 7 years ago
nobu (Nobuyoshi Nakada) wrote:
Weakref is implemented by finalizer to notify that an object is collected, and you can't define finalizers on frozen objects.
Probably we need to move finalizer flags to a separate region (like bitmap marking).
Yes please. I also came here having discovered this independently, and also see it as a bug. It makes designs using frozen objects difficult to this friction with a leaky abstraction in the language implementation.
Unless I am mistaken, and mutating objects is an intentional part of the design of the GC system?
Updated by nobu (Nobuyoshi Nakada) over 5 years ago
- Status changed from Assigned to Closed
Applied in changeset git|f3c81b4e90ec492382e299573f2c3ac272adbb5f.
Frozen objects in WeakMap
- gc.c (wmap_aset): bypass check for frozen and allow frozen
object in WeakMap. [Bug #13498]