upb_extreg, upb_msg
diff --git a/python/message.c b/python/message.c
index e2ac314..37d0aec 100644
--- a/python/message.c
+++ b/python/message.c
@@ -192,7 +192,7 @@
   uintptr_t def;  // Tagged, low bit 1 == upb_FieldDef*, else upb_MessageDef*
   union {
     // when def is msgdef, the data for this msg.
-    upb_msg* msg;
+    upb_Message* msg;
     // when def is fielddef, owning pointer to parent
     struct PyUpb_CMessage* parent;
   } ptr;
@@ -221,7 +221,7 @@
   return _PyUpb_CMessage_GetMsgdef((PyUpb_CMessage*)self);
 }
 
-static upb_msg* PyUpb_CMessage_GetMsg(PyUpb_CMessage* self) {
+static upb_Message* PyUpb_CMessage_GetMsg(PyUpb_CMessage* self) {
   assert(!PyUpb_CMessage_IsStub(self));
   return self->ptr.msg;
 }
@@ -243,7 +243,7 @@
 
 // If the message is reified, returns it.  Otherwise, returns NULL.
 // If NULL is returned, the object is empty and has no underlying data.
-upb_msg* PyUpb_CMessage_GetIfReified(PyObject* _self) {
+upb_Message* PyUpb_CMessage_GetIfReified(PyObject* _self) {
   PyUpb_CMessage* self = (void*)_self;
   return PyUpb_CMessage_IsStub(self) ? NULL : self->ptr.msg;
 }
@@ -422,7 +422,7 @@
   return ok;
 }
 
-static bool PyUpb_CMessage_InitScalarAttribute(upb_msg* msg,
+static bool PyUpb_CMessage_InitScalarAttribute(upb_Message* msg,
                                                const upb_FieldDef* f,
                                                PyObject* value,
                                                upb_Arena* arena) {
@@ -449,7 +449,7 @@
   PyObject* name;
   PyObject* value;
   PyUpb_CMessage_EnsureReified(self);
-  upb_msg* msg = PyUpb_CMessage_GetMsg(self);
+  upb_Message* msg = PyUpb_CMessage_GetMsg(self);
   upb_Arena* arena = PyUpb_Arena_Get(self->arena);
 
   while (PyDict_Next(kwargs, &pos, &name, &value)) {
@@ -520,8 +520,8 @@
   const upb_MessageDef* m2_msgdef = _PyUpb_CMessage_GetMsgdef(m2);
   assert(m1_msgdef == m2_msgdef);
 #endif
-  const upb_msg* m1_msg = PyUpb_CMessage_GetIfReified((PyObject*)m1);
-  const upb_msg* m2_msg = PyUpb_CMessage_GetIfReified(_m2);
+  const upb_Message* m1_msg = PyUpb_CMessage_GetIfReified((PyObject*)m1);
+  const upb_Message* m2_msg = PyUpb_CMessage_GetIfReified(_m2);
   return PyUpb_Message_IsEqual(m1_msg, m2_msg, m1_msgdef);
 }
 
@@ -566,8 +566,8 @@
   if (!PyUpb_CMessage_IsStub(self)) return;
   upb_Arena* arena = PyUpb_Arena_Get(self->arena);
 
-  // This is a non-present message. We need to create a real upb_msg for this
-  // object and every parent until we reach a present message.
+  // This is a non-present message. We need to create a real upb_Message for
+  // this object and every parent until we reach a present message.
   PyUpb_CMessage* child = self;
   PyUpb_CMessage* parent = self->ptr.parent;
   const upb_FieldDef* child_f = PyUpb_CMessage_InitAsMsg(child, arena);
@@ -600,7 +600,7 @@
  * the set state (having a non-owning pointer to self->ptr.msg).
  */
 static void PyUpb_CMessage_Reify(PyUpb_CMessage* self, const upb_FieldDef* f,
-                                 upb_msg* msg) {
+                                 upb_Message* msg) {
   assert(f == PyUpb_CMessage_GetFieldDef(self));
   if (!msg) {
     const upb_MessageDef* msgdef = PyUpb_CMessage_GetMsgdef((PyObject*)self);
@@ -616,7 +616,7 @@
 /*
  * PyUpb_CMessage_SyncSubobjs()
  *
- * This operation must be invoked whenever the underlying upb_msg has been
+ * This operation must be invoked whenever the underlying upb_Message has been
  * mutated directly in C.  This will attach any newly-present field data
  * to previously returned stub wrapper objects.
  *
@@ -635,7 +635,7 @@
   PyUpb_WeakMap* subobj_map = self->unset_subobj_map;
   if (!subobj_map) return;
 
-  upb_msg* msg = PyUpb_CMessage_GetMsg(self);
+  upb_Message* msg = PyUpb_CMessage_GetMsg(self);
   intptr_t iter = PYUPB_WEAKMAP_BEGIN;
   const void* key;
   PyObject* obj;
@@ -661,7 +661,7 @@
     } else {
       PyUpb_CMessage* sub = (void*)obj;
       assert(self == sub->ptr.parent);
-      PyUpb_CMessage_Reify(sub, f, (upb_msg*)msgval.msg_val);
+      PyUpb_CMessage_Reify(sub, f, (upb_Message*)msgval.msg_val);
     }
   }
 
@@ -675,7 +675,7 @@
   if (PyUpb_CMessage_IsStub(self)) {
     return PyUnicode_FromStringAndSize(NULL, 0);
   }
-  upb_msg* msg = PyUpb_CMessage_GetMsg(self);
+  upb_Message* msg = PyUpb_CMessage_GetMsg(self);
   const upb_MessageDef* msgdef = _PyUpb_CMessage_GetMsgdef(self);
   const upb_DefPool* symtab = upb_FileDef_Pool(upb_MessageDef_File(msgdef));
   char buf[1024];
@@ -749,7 +749,7 @@
   }
 }
 
-PyObject* PyUpb_CMessage_Get(upb_msg* u_msg, const upb_MessageDef* m,
+PyObject* PyUpb_CMessage_Get(upb_Message* u_msg, const upb_MessageDef* m,
                              PyObject* arena) {
   PyObject* ret = PyUpb_ObjCache_Get(u_msg);
   if (ret) return ret;
@@ -1011,7 +1011,7 @@
   } else {
     // We just need to return a boolean "true" or "false" for whether all
     // required fields are set.
-    upb_msg* msg = PyUpb_CMessage_GetIfReified(_self);
+    upb_Message* msg = PyUpb_CMessage_GetIfReified(_self);
     const upb_MessageDef* m = PyUpb_CMessage_GetMsgdef(_self);
     const upb_DefPool* symtab = upb_FileDef_Pool(upb_MessageDef_File(m));
     bool initialized = !upb_util_HasUnsetRequired(msg, m, symtab, NULL);
@@ -1052,7 +1052,7 @@
 
 static PyObject* PyUpb_CMessage_ListFields(PyObject* _self, PyObject* arg) {
   PyObject* list = PyList_New(0);
-  upb_msg* msg = PyUpb_CMessage_GetIfReified(_self);
+  upb_Message* msg = PyUpb_CMessage_GetIfReified(_self);
   if (!msg) return list;
 
   size_t iter1 = kUpb_Message_Begin;
@@ -1145,7 +1145,7 @@
   PyUpb_CMessage_EnsureReified(self);
   const upb_MessageDef* msgdef = _PyUpb_CMessage_GetMsgdef(self);
   const upb_FileDef* file = upb_MessageDef_File(msgdef);
-  const upb_extreg* extreg =
+  const upb_ExtensionRegistry* extreg =
       upb_DefPool_ExtensionRegistry(upb_FileDef_Pool(file));
   const upb_MiniTable* layout = upb_MessageDef_MiniTable(msgdef);
   upb_Arena* arena = PyUpb_Arena_Get(self->arena);
@@ -1190,7 +1190,7 @@
   PyUpb_WeakMap* subobj_map = self->unset_subobj_map;
 
   if (subobj_map) {
-    upb_msg* msg = PyUpb_CMessage_GetMsg(self);
+    upb_Message* msg = PyUpb_CMessage_GetMsg(self);
     intptr_t iter = PYUPB_WEAKMAP_BEGIN;
     const void* key;
     PyObject* obj;
@@ -1290,7 +1290,7 @@
 static PyObject* PyUpb_CMessage_FindInitializationErrors(PyObject* _self,
                                                          PyObject* arg) {
   PyUpb_CMessage* self = (void*)_self;
-  upb_msg* msg = PyUpb_CMessage_GetIfReified(_self);
+  upb_Message* msg = PyUpb_CMessage_GetIfReified(_self);
   const upb_MessageDef* msgdef = _PyUpb_CMessage_GetMsgdef(self);
   const upb_DefPool* ext_pool = upb_FileDef_Pool(upb_MessageDef_File(msgdef));
   upb_FieldPathEntry* fields;
@@ -1363,7 +1363,7 @@
 
 static PyObject* PyUpb_CMessage_HasExtension(PyObject* _self,
                                              PyObject* ext_desc) {
-  upb_msg* msg = PyUpb_CMessage_GetIfReified(_self);
+  upb_Message* msg = PyUpb_CMessage_GetIfReified(_self);
   const upb_FieldDef* f = PyUpb_CMessage_GetExtensionDef(_self, ext_desc);
   if (!f) return NULL;
   if (upb_FieldDef_IsRepeated(f)) {
@@ -1465,7 +1465,7 @@
   if (!PyUpb_CMessage_LookupName(self, name, NULL, &o, PyExc_ValueError)) {
     return NULL;
   }
-  upb_msg* msg = PyUpb_CMessage_GetIfReified(_self);
+  upb_Message* msg = PyUpb_CMessage_GetIfReified(_self);
   if (!msg) Py_RETURN_NONE;
   const upb_FieldDef* f = upb_Message_WhichOneof(msg, o);
   if (!f) Py_RETURN_NONE;