Fix an infinite recursion issue with native extensions that redefine frozen?.

MRI defines `frozen?` with `rb_obj_frozen_p`, which in turn, uses `RB_OBJ_FROZEN`. Since TruffleRuby doesn't have flag bits in an object header like MRI does, we implement `RB_OBJ_FROZEN` with `rb_obj_frozen_p`, which would lead to an infinite loop if a native extension redefined `frozen?` in terms of `RB_OBJ_FROZEN`. We break the loop by introducing a new primitive, which a native extension would not be able to redefine.

Author: nirvdrum

CHANGELOG.md

@@ -6,6 +6,7 @@ New features:
 Bug fixes:
 
 * Fix `Range#cover?` on begin-less ranges and non-integer values (@nirvdrum, @rwstauner).
+* Fix a possible case of infinite recursion when implementing `frozen?` in a native extension (@nirvdrum).
 
 Compatibility:
 

lib/truffle/truffle/cext.rb

@@ -471,7 +471,7 @@ def rb_obj_freeze(obj)
   end
 
   def rb_obj_frozen_p(object)
-    object.frozen?
+    Primitive.frozen?(object)
   end
 
   def rb_obj_id(object)

src/main/java/org/truffleruby/core/support/TypeNodes.java

@@ -161,6 +161,15 @@ Object freeze(Object self,
         }
     }
 
+    @Primitive(name = "frozen?")
+    public abstract static class IsFrozenPrimitive extends PrimitiveArrayArgumentsNode {
+        @Specialization
+        boolean isFrozen(Object self,
+                @Cached IsFrozenNode isFrozenNode) {
+            return isFrozenNode.execute(self);
+        }
+    }
+
     @Primitive(name = "immediate_value?")
     public abstract static class IsImmediateValueNode extends PrimitiveArrayArgumentsNode {