Bug #21343: Namespace: singleton classes of root namespace leak between namespaces

• Status: Open
• Assignee: -
• Target version: -
• Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN

[jhawthorn (John Hawthorn)]

Ruby classes all have singleton classes, those singleton classes have singleton classes, and so on with infinite nesting. Since we don't have infinite resources, we create these lazily.

Because of this, only a certain number of singleton classes exist in the root namespace. At a certain depth, mutable singleton classes end up shared between namespaces.

File.write("/tmp/ntest.rb", <<~'RUBY')
  p String.singleton_class.singleton_class::Foo
  String.singleton_class.singleton_class::Bar = 456
RUBY

String.singleton_class.singleton_class::Foo = 123

ns = Namespace.new
ns.require("/tmp/ntest.rb")

p String.singleton_class.singleton_class::Bar

RUBY_NAMESPACE=1 ruby nstest2.rb
ruby: warning: Namespace is experimental, and the behavior may change in the future!
See doc/namespace.md for known issues, etc.
123
456

[byroot (Jean Boussier)]

Seems adjacent to https://bugs.ruby-lang.org/issues/21330.

The klass field like the flags one isn't part of the classext_t, so it's not effectively namespaced.