From 3072f9fd82c17049a5b54336cefc659724f5d661 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sat, 18 Apr 2020 13:56:13 +0200
Subject: [PATCH] LibJS: Move the empty object shape from Interpreter to
 GlobalObject

The big remaining hurdle before a GlobalObject-agnostic Interpreter is
the fact that Interpreter owns and vends the GlobalObject :^)
---
 Libraries/LibJS/Interpreter.cpp          | 2 --
 Libraries/LibJS/Interpreter.h            | 3 ---
 Libraries/LibJS/Runtime/GlobalObject.cpp | 3 +++
 Libraries/LibJS/Runtime/GlobalObject.h   | 4 ++++
 Libraries/LibJS/Runtime/Object.cpp       | 8 ++++++--
 5 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/Libraries/LibJS/Interpreter.cpp b/Libraries/LibJS/Interpreter.cpp
index b34d507884..24fdb5f49d 100644
--- a/Libraries/LibJS/Interpreter.cpp
+++ b/Libraries/LibJS/Interpreter.cpp
@@ -40,7 +40,6 @@ namespace JS {
 Interpreter::Interpreter()
     : m_heap(*this)
 {
-    m_empty_object_shape = heap().allocate<Shape>();
 }
 
 Interpreter::~Interpreter()
@@ -161,7 +160,6 @@ Optional<Value> Interpreter::get_variable(const FlyString& name)
 
 void Interpreter::gather_roots(Badge<Heap>, HashTable<Cell*>& roots)
 {
-    roots.set(m_empty_object_shape);
     roots.set(m_global_object);
     roots.set(m_exception);
 
diff --git a/Libraries/LibJS/Interpreter.h b/Libraries/LibJS/Interpreter.h
index de9cbb3717..a6f54d97aa 100644
--- a/Libraries/LibJS/Interpreter.h
+++ b/Libraries/LibJS/Interpreter.h
@@ -139,8 +139,6 @@ public:
         return m_call_stack.last().this_value;
     }
 
-    Shape* empty_object_shape() { return m_empty_object_shape; }
-
     Exception* exception()
     {
         return m_exception;
@@ -171,7 +169,6 @@ private:
     Vector<ScopeFrame> m_scope_stack;
     Vector<CallFrame> m_call_stack;
 
-    Shape* m_empty_object_shape { nullptr };
     Object* m_global_object { nullptr };
 
     Exception* m_exception { nullptr };
diff --git a/Libraries/LibJS/Runtime/GlobalObject.cpp b/Libraries/LibJS/Runtime/GlobalObject.cpp
index 0ff1d13fef..317fd32eed 100644
--- a/Libraries/LibJS/Runtime/GlobalObject.cpp
+++ b/Libraries/LibJS/Runtime/GlobalObject.cpp
@@ -72,6 +72,7 @@ GlobalObject::GlobalObject()
 void GlobalObject::initialize()
 {
     // These are done first since other prototypes depend on their presence.
+    m_empty_object_shape = heap().allocate<Shape>();
     m_object_prototype = heap().allocate<ObjectPrototype>();
     m_function_prototype = heap().allocate<FunctionPrototype>();
 
@@ -119,6 +120,8 @@ void GlobalObject::visit_children(Visitor& visitor)
 {
     Object::visit_children(visitor);
 
+    visitor.visit(m_empty_object_shape);
+
 #define __JS_ENUMERATE(ClassName, snake_name, PrototypeName, ConstructorName) \
     visitor.visit(m_##snake_name##_constructor);
     JS_ENUMERATE_ERROR_SUBCLASSES
diff --git a/Libraries/LibJS/Runtime/GlobalObject.h b/Libraries/LibJS/Runtime/GlobalObject.h
index 2f349dd86e..52ca09a3a0 100644
--- a/Libraries/LibJS/Runtime/GlobalObject.h
+++ b/Libraries/LibJS/Runtime/GlobalObject.h
@@ -37,6 +37,8 @@ public:
 
     virtual ~GlobalObject() override;
 
+    Shape* empty_object_shape() { return m_empty_object_shape; }
+
 #define __JS_ENUMERATE(ClassName, snake_name, PrototypeName, ConstructorName)            \
     ConstructorName* snake_name##_constructor() { return m_##snake_name##_constructor; } \
     Object* snake_name##_prototype() { return m_##snake_name##_prototype; }
@@ -55,6 +57,8 @@ private:
     template<typename ConstructorType>
     void add_constructor(const FlyString& property_name, ConstructorType*&, Object& prototype);
 
+    Shape* m_empty_object_shape { nullptr };
+
 #define __JS_ENUMERATE(ClassName, snake_name, PrototypeName, ConstructorName) \
     ConstructorName* m_##snake_name##_constructor { nullptr };                \
     Object* m_##snake_name##_prototype { nullptr };
diff --git a/Libraries/LibJS/Runtime/Object.cpp b/Libraries/LibJS/Runtime/Object.cpp
index f35205dffc..bc9affce08 100644
--- a/Libraries/LibJS/Runtime/Object.cpp
+++ b/Libraries/LibJS/Runtime/Object.cpp
@@ -45,8 +45,12 @@ Object* Object::create_empty(Interpreter&, GlobalObject& global_object)
 
 Object::Object(Object* prototype)
 {
-    m_shape = interpreter().empty_object_shape();
-    set_prototype(prototype);
+    if (prototype) {
+        m_shape = interpreter().global_object().empty_object_shape();
+        set_prototype(prototype);
+    } else {
+        m_shape = interpreter().heap().allocate<Shape>();
+    }
 }
 
 Object::~Object()