From 82d72f14e7071218f3fd710f770d1ba31390f027 Mon Sep 17 00:00:00 2001 From: nagachika Date: Sat, 20 Mar 2021 14:26:30 +0900 Subject: merge revision(s) ebb96fa8808317ad53a4977bff26cf755d68077e: [Backport #17321] 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 --- class.c | 31 ++++++++++++++++++++++--------- test/ruby/test_class.rb | 47 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 69 insertions(+), 9 deletions(-) --- class.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) (limited to 'class.c') diff --git a/class.c b/class.c index c866d1d727..2e4b31d7c6 100644 --- a/class.c +++ b/class.c @@ -32,6 +32,9 @@ #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) { @@ -372,22 +375,35 @@ rb_singleton_class_clone(VALUE obj) 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)); @@ -411,7 +427,9 @@ rb_singleton_class_clone_and_attach(VALUE obj, VALUE attach) 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; @@ -433,11 +451,6 @@ rb_singleton_class_attached(VALUE klass, VALUE obj) } } - - -#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) -- cgit v1.2.3