Allocate singleton classes as namespaceable if their parent are

Author: byroot

class.c

@@ -644,14 +644,18 @@ class_switch_superclass(VALUE super, VALUE klass)
  * @note this function is not Class#allocate.
  */
 static VALUE
-class_alloc(enum ruby_value_type type, VALUE klass)
+class_alloc0(enum ruby_value_type type, VALUE klass, bool namespaceable)
 {
     rb_ns_subclasses_t *ns_subclasses;
     rb_subclass_anchor_t *anchor;
     const rb_namespace_t *ns = rb_definition_namespace();
 
-    size_t alloc_size = sizeof(struct RClass_and_rb_classext_t);
     if (!ruby_namespace_init_done) {
+        namespaceable = true;
+    }
+
+    size_t alloc_size = sizeof(struct RClass_and_rb_classext_t);
+    if (namespaceable) {
         alloc_size = sizeof(struct RClass_namespaceable);
     }
 
@@ -672,7 +676,7 @@ class_alloc(enum ruby_value_type type, VALUE klass)
 
     VALUE flags = type;
     if (RGENGC_WB_PROTECTED_CLASS) flags |= FL_WB_PROTECTED;
-    if (!ruby_namespace_init_done) flags |= RCLASS_NAMESPACEABLE;
+    if (namespaceable) flags |= RCLASS_NAMESPACEABLE;
 
     NEWOBJ_OF(obj, struct RClass, klass, flags, alloc_size, 0);
 
@@ -688,7 +692,7 @@ class_alloc(enum ruby_value_type type, VALUE klass)
     RCLASS_PRIME_NS((VALUE)obj) = ns;
     // Classes/Modules defined in user namespaces are
     // writable directly because it exists only in a namespace.
-    RCLASS_SET_PRIME_CLASSEXT_WRITABLE((VALUE)obj, ruby_namespace_init_done || NAMESPACE_USER_P(ns));
+    RCLASS_SET_PRIME_CLASSEXT_WRITABLE((VALUE)obj, !namespaceable || NAMESPACE_USER_P(ns));
 
     RCLASS_SET_ORIGIN((VALUE)obj, (VALUE)obj);
     RCLASS_SET_REFINED_CLASS((VALUE)obj, Qnil);
@@ -698,6 +702,12 @@ class_alloc(enum ruby_value_type type, VALUE klass)
     return (VALUE)obj;
 }
 
+static VALUE
+class_alloc(enum ruby_value_type type, VALUE klass)
+{
+    return class_alloc0(type, klass, false);
+}
+
 static VALUE
 class_associate_super(VALUE klass, VALUE super, bool init)
 {
@@ -733,19 +743,10 @@ class_clear_method_table(VALUE c)
     RCLASS_WRITE_M_TBL_EVEN_WHEN_PROMOTED(c, rb_id_table_create(0));
 }
 
-/**
- * A utility function that wraps class_alloc.
- *
- * allocates a class and initializes safely.
- * @param super     a class from which the new class derives.
- * @return          a class object.
- * @pre  `super` must be a class.
- * @post the metaclass of the new class is Class.
- */
-VALUE
-rb_class_boot(VALUE super)
+static VALUE
+class_boot_namespaceable(VALUE super, bool namespaceable)
 {
-    VALUE klass = class_alloc(T_CLASS, rb_cClass);
+    VALUE klass = class_alloc0(T_CLASS, rb_cClass, namespaceable);
 
     // initialize method table prior to class_associate_super()
     // because class_associate_super() may cause GC and promote klass
@@ -759,6 +760,21 @@ rb_class_boot(VALUE super)
     return (VALUE)klass;
 }
 
+/**
+ * A utility function that wraps class_alloc.
+ *
+ * allocates a class and initializes safely.
+ * @param super     a class from which the new class derives.
+ * @return          a class object.
+ * @pre  `super` must be a class.
+ * @post the metaclass of the new class is Class.
+ */
+VALUE
+rb_class_boot(VALUE super)
+{
+    return class_boot_namespaceable(super, false);
+}
+
 static VALUE *
 class_superclasses_including_self(VALUE klass)
 {
@@ -1254,7 +1270,7 @@ static inline VALUE
 make_metaclass(VALUE klass)
 {
     VALUE super;
-    VALUE metaclass = rb_class_boot(Qundef);
+    VALUE metaclass = class_boot_namespaceable(Qundef, FL_TEST_RAW(klass, RCLASS_NAMESPACEABLE));
 
     FL_SET(metaclass, FL_SINGLETON);
     rb_singleton_class_attached(metaclass, klass);
@@ -1290,7 +1306,7 @@ static inline VALUE
 make_singleton_class(VALUE obj)
 {
     VALUE orig_class = METACLASS_OF(obj);
-    VALUE klass = rb_class_boot(orig_class);
+    VALUE klass = class_boot_namespaceable(orig_class, FL_TEST_RAW(orig_class, RCLASS_NAMESPACEABLE));
 
     FL_SET(klass, FL_SINGLETON);
     RBASIC_SET_CLASS(obj, klass);