ruby-changes:63619
From: Alan <ko1@a...>
Date: Tue, 17 Nov 2020 07:41:33 +0900 (JST)
Subject: [ruby-changes:63619] ebb96fa880 (master): Fix singleton class cloning
https://git.ruby-lang.org/ruby.git/commit/?id=ebb96fa880 From ebb96fa8808317ad53a4977bff26cf755d68077e Mon Sep 17 00:00:00 2001 From: Alan Wu <XrXr@u...> Date: Wed, 11 Nov 2020 16:38:03 -0500 Subject: Fix singleton class cloning Before this commit, `clone` gave different results depending on whether the original object had an attached singleton class or not. Consider the following setup: ``` class Foo; end Foo.singleton_class.define_method(:foo) {} obj = Foo.new obj.singleton_class if $call_singleton clone = obj.clone ``` When `$call_singleton = false`, neither `obj.singleton_class.singleton_class` nor `clone.singleton_class.singleton_class` own any methods. However, when `$call_singleton = true`, `clone.singleton_class.singleton_class` would own a copy of `foo` from `Foo.singleton_class`, even though `obj.singleton_class.singleton_class` does not. The latter case is unexpected and results in a visibly different clone, depending on if the original object had an attached class or not. Co-authored-by: Ufuk Kayserilioglu <ufuk.kayserilioglu@s...> diff --git a/class.c b/class.c index 48450a5..709d49c 100644 --- a/class.c +++ b/class.c @@ -40,6 +40,9 @@ https://github.com/ruby/ruby/blob/trunk/class.c#L40 #define id_attached id__attached__ +#define METACLASS_OF(k) RBASIC(k)->klass +#define SET_METACLASS_OF(k, cls) RBASIC_SET_CLASS(k, cls) + void rb_class_subclass_add(VALUE super, VALUE klass) { @@ -457,22 +460,35 @@ rb_singleton_class_clone(VALUE obj) https://github.com/ruby/ruby/blob/trunk/class.c#L460 return rb_singleton_class_clone_and_attach(obj, Qundef); } +// Clone and return the singleton class of `obj` if it has been created and is attached to `obj`. VALUE rb_singleton_class_clone_and_attach(VALUE obj, VALUE attach) { const VALUE klass = RBASIC(obj)->klass; - if (!FL_TEST(klass, FL_SINGLETON)) - return klass; + // Note that `rb_singleton_class()` can create situations where `klass` is + // attached to an object other than `obj`. In which case `obj` does not have + // a material singleton class attached yet and there is no singleton class + // to clone. + if (!(FL_TEST(klass, FL_SINGLETON) && rb_attr_get(klass, id_attached) == obj)) { + // nothing to clone + return klass; + } else { /* copy singleton(unnamed) class */ + bool klass_of_clone_is_new; VALUE clone = class_alloc(RBASIC(klass)->flags, 0); if (BUILTIN_TYPE(obj) == T_CLASS) { + klass_of_clone_is_new = true; RBASIC_SET_CLASS(clone, clone); } else { - RBASIC_SET_CLASS(clone, rb_singleton_class_clone(klass)); + VALUE klass_metaclass_clone = rb_singleton_class_clone(klass); + // When `METACLASS_OF(klass) == klass_metaclass_clone`, it means the + // recursive call did not clone `METACLASS_OF(klass)`. + klass_of_clone_is_new = (METACLASS_OF(klass) != klass_metaclass_clone); + RBASIC_SET_CLASS(clone, klass_metaclass_clone); } RCLASS_SET_SUPER(clone, RCLASS_SUPER(klass)); @@ -496,7 +512,9 @@ rb_singleton_class_clone_and_attach(VALUE obj, VALUE attach) https://github.com/ruby/ruby/blob/trunk/class.c#L512 arg.new_klass = clone; rb_id_table_foreach(RCLASS_M_TBL(klass), clone_method_i, &arg); } - rb_singleton_class_attached(RBASIC(clone)->klass, clone); + if (klass_of_clone_is_new) { + rb_singleton_class_attached(RBASIC(clone)->klass, clone); + } FL_SET(clone, FL_SINGLETON); return clone; @@ -518,11 +536,6 @@ rb_singleton_class_attached(VALUE klass, VALUE obj) https://github.com/ruby/ruby/blob/trunk/class.c#L536 } } - - -#define METACLASS_OF(k) RBASIC(k)->klass -#define SET_METACLASS_OF(k, cls) RBASIC_SET_CLASS(k, cls) - /*! * whether k is a meta^(n)-class of Class class * @retval 1 if \a k is a meta^(n)-class of Class class (n >= 0) diff --git a/test/ruby/test_class.rb b/test/ruby/test_class.rb index 82a2e55..6a8234a 100644 --- a/test/ruby/test_class.rb +++ b/test/ruby/test_class.rb @@ -483,6 +483,53 @@ class TestClass < Test::Unit::TestCase https://github.com/ruby/ruby/blob/trunk/test/ruby/test_class.rb#L483 assert_equal(:foo, d.foo) end + def test_clone_singleton_class_exists + klass = Class.new do + def self.bar; :bar; end + end + + o = klass.new + o.singleton_class + clone = o.clone + + assert_empty(o.singleton_class.instance_methods(false)) + assert_empty(clone.singleton_class.instance_methods(false)) + assert_empty(o.singleton_class.singleton_class.instance_methods(false)) + assert_empty(clone.singleton_class.singleton_class.instance_methods(false)) + end + + def test_clone_when_singleton_class_of_singleton_class_exists + klass = Class.new do + def self.bar; :bar; end + end + + o = klass.new + o.singleton_class.singleton_class + clone = o.clone + + assert_empty(o.singleton_class.instance_methods(false)) + assert_empty(clone.singleton_class.instance_methods(false)) + assert_empty(o.singleton_class.singleton_class.instance_methods(false)) + assert_empty(clone.singleton_class.singleton_class.instance_methods(false)) + end + + def test_clone_when_method_exists_on_singleton_class_of_singleton_class + klass = Class.new do + def self.bar; :bar; end + end + + o = klass.new + o.singleton_class.singleton_class.define_method(:s2_method) { :s2 } + clone = o.clone + + assert_empty(o.singleton_class.instance_methods(false)) + assert_empty(clone.singleton_class.instance_methods(false)) + assert_equal(:s2, o.singleton_class.s2_method) + assert_equal(:s2, clone.singleton_class.s2_method) + assert_equal([:s2_method], o.singleton_class.singleton_class.instance_methods(false)) + assert_equal([:s2_method], clone.singleton_class.singleton_class.instance_methods(false)) + end + def test_singleton_class_p feature7609 = '[ruby-core:51087] [Feature #7609]' assert_predicate(self.singleton_class, :singleton_class?, feature7609) -- cgit v0.10.2 -- ML: ruby-changes@q... Info: http://www.atdot.net/~ko1/quickml/