Update current namespace management by using control frames and lexical contexts

to fix inconsistent and wrong current namespace detections.

This includes:
* Moving load_path and related things from rb_vm_t to rb_namespace_t to simplify
  accessing those values via namespace (instead of accessing either vm or ns)
* Initializing root_namespace earlier and consolidate builtin_namespace into root_namespace
* Adding VM_FRAME_FLAG_NS_REQUIRE for checkpoints to detect a namespace to load/require files
* Removing implicit refinements in the root namespace which was used to determine
  the namespace to be loaded (replaced by VM_FRAME_FLAG_NS_REQUIRE)
* Removing namespaces from rb_proc_t because its namespace can be identified by lexical context
* Starting to use ep[VM_ENV_DATA_INDEX_SPECVAL] to store the current namespace when
  the frame type is MAGIC_TOP or MAGIC_CLASS (block handlers don't exist in this case)

3 files changed, 16 insertions, 24 deletions

diff --git a/internal/class.h b/internal/class.h
index bed69adef7..29b3526cf5 100644
--- a/internal/class.h
+++ b/internal/class.h
@@ -390,8 +390,7 @@ RCLASS_EXT_READABLE_LOOKUP(VALUE obj, const rb_namespace_t *ns)
 static inline rb_classext_t *
 RCLASS_EXT_READABLE_IN_NS(VALUE obj, const rb_namespace_t *ns)
 {
-    if (!ns
-        || NAMESPACE_BUILTIN_P(ns)
+    if (NAMESPACE_ROOT_P(ns)
         || RCLASS_PRIME_CLASSEXT_READABLE_P(obj)) {
         return RCLASS_EXT_PRIME(obj);
     }
@@ -405,9 +404,9 @@ RCLASS_EXT_READABLE(VALUE obj)
     if (RCLASS_PRIME_CLASSEXT_READABLE_P(obj)) {
         return RCLASS_EXT_PRIME(obj);
     }
-    // delay namespace loading to optimize for unmodified classes
+    // delay determining the current namespace to optimize for unmodified classes
     ns = rb_current_namespace();
-    if (!ns || NAMESPACE_BUILTIN_P(ns)) {
+    if (NAMESPACE_ROOT_P(ns)) {
         return RCLASS_EXT_PRIME(obj);
     }
     return RCLASS_EXT_READABLE_LOOKUP(obj, ns);
@@ -440,8 +439,7 @@ RCLASS_EXT_WRITABLE_LOOKUP(VALUE obj, const rb_namespace_t *ns)
 static inline rb_classext_t *
 RCLASS_EXT_WRITABLE_IN_NS(VALUE obj, const rb_namespace_t *ns)
 {
-    if (!ns
-        || NAMESPACE_BUILTIN_P(ns)
+    if (NAMESPACE_ROOT_P(ns)
         || RCLASS_PRIME_CLASSEXT_WRITABLE_P(obj)) {
         return RCLASS_EXT_PRIME(obj);
     }
@@ -455,11 +453,9 @@ RCLASS_EXT_WRITABLE(VALUE obj)
     if (LIKELY(RCLASS_PRIME_CLASSEXT_WRITABLE_P(obj))) {
         return RCLASS_EXT_PRIME(obj);
     }
-    // delay namespace loading to optimize for unmodified classes
+    // delay determining the current namespace to optimize for unmodified classes
     ns = rb_current_namespace();
-    if (!ns || NAMESPACE_BUILTIN_P(ns)) {
-        // If no namespace is specified, Ruby VM is in bootstrap
-        // and the clean class definition is under construction.
+    if (NAMESPACE_ROOT_P(ns)) {
         return RCLASS_EXT_PRIME(obj);
     }
     return RCLASS_EXT_WRITABLE_LOOKUP(obj, ns);
diff --git a/internal/inits.h b/internal/inits.h
index e618d87cc3..c1cf3db94d 100644
--- a/internal/inits.h
+++ b/internal/inits.h
@@ -32,6 +32,9 @@ void Init_enable_namespace(void);
 void Init_BareVM(void);
 void Init_vm_objects(void);
 
+/* namespace.c */
+void Init_root_namespace(void);
+
 /* vm_backtrace.c */
 void Init_vm_backtrace(void);
 
diff --git a/internal/namespace.h b/internal/namespace.h
index 4cdfbc305f..c68f0987aa 100644
--- a/internal/namespace.h
+++ b/internal/namespace.h
@@ -35,13 +35,14 @@ struct rb_namespace_struct {
 
     VALUE gvar_tbl;
 
-    bool is_builtin;
     bool is_user;
     bool is_optional;
 };
 typedef struct rb_namespace_struct rb_namespace_t;
 
-#define NAMESPACE_BUILTIN_P(ns) (ns && ns->is_builtin)
+#define NAMESPACE_OBJ_P(obj) (CLASS_OF(obj) == rb_cNamespace)
+
+#define NAMESPACE_ROOT_P(ns) (ns && !ns->is_user)
 #define NAMESPACE_USER_P(ns) (ns && ns->is_user)
 #define NAMESPACE_OPTIONAL_P(ns) (ns && ns->is_optional)
 #define NAMESPACE_MAIN_P(ns) (ns && ns->is_user && !ns->is_optional)
@@ -60,24 +61,16 @@ rb_namespace_available(void)
     return ruby_namespace_enabled;
 }
 
-void rb_namespace_enable_builtin(void);
-void rb_namespace_disable_builtin(void);
-void rb_namespace_push_loading_namespace(const rb_namespace_t *);
-void rb_namespace_pop_loading_namespace(const rb_namespace_t *);
-rb_namespace_t * rb_root_namespace(void);
-const rb_namespace_t *rb_builtin_namespace(void);
-rb_namespace_t * rb_main_namespace(void);
-const rb_namespace_t * rb_definition_namespace(void);
-const rb_namespace_t * rb_loading_namespace(void);
+const rb_namespace_t * rb_root_namespace(void);
+const rb_namespace_t * rb_main_namespace(void);
 const rb_namespace_t * rb_current_namespace(void);
-VALUE rb_current_namespace_details(VALUE);
+const rb_namespace_t * rb_loading_namespace(void);
 
 void rb_namespace_entry_mark(void *);
+void rb_namespace_gc_update_references(void *ptr);
 
 rb_namespace_t * rb_get_namespace_t(VALUE ns);
 VALUE rb_get_namespace_object(rb_namespace_t *ns);
-typedef VALUE namespace_exec_func(VALUE arg);
-VALUE rb_namespace_exec(const rb_namespace_t *ns, namespace_exec_func *func, VALUE arg);
 
 VALUE rb_namespace_local_extension(VALUE namespace, VALUE fname, VALUE path);