diff --git a/upb/message/accessors.h b/upb/message/accessors.h
index 7e6f8178de..12b81ce9a1 100644
--- a/upb/message/accessors.h
+++ b/upb/message/accessors.h
@@ -379,7 +379,8 @@ UPB_API_INLINE upb_Array* upb_Message_GetOrCreateMutableArray(
   _upb_MiniTableField_CheckIsArray(field);
   upb_Array* array = upb_Message_GetMutableArray(msg, field);
   if (!array) {
-    array = _upb_Array_New(arena, 4, _upb_MiniTableField_ElemSizeLg2(field));
+    array = UPB_PRIVATE(_upb_Array_New)(arena, 4,
+                                        _upb_MiniTableField_ElemSizeLg2(field));
     // Check again due to: https://godbolt.org/z/7WfaoKG1r
     _upb_MiniTableField_CheckIsArray(field);
     upb_MessageValue val;
diff --git a/upb/message/array.c b/upb/message/array.c
index 40264ea340..ba3f743010 100644
--- a/upb/message/array.c
+++ b/upb/message/array.c
@@ -19,7 +19,7 @@
 #include "upb/port/def.inc"
 
 upb_Array* upb_Array_New(upb_Arena* a, upb_CType type) {
-  return _upb_Array_New(a, 4, upb_CType_SizeLg2(type));
+  return UPB_PRIVATE(_upb_Array_New)(a, 4, upb_CType_SizeLg2(type));
 }
 
 const void* upb_Array_DataPtr(const upb_Array* arr) {
@@ -33,7 +33,7 @@ size_t upb_Array_Size(const upb_Array* arr) { return arr->size; }
 upb_MessageValue upb_Array_Get(const upb_Array* arr, size_t i) {
   upb_MessageValue ret;
   const char* data = _upb_array_constptr(arr);
-  const int lg2 = _upb_Array_ElemSizeLg2(arr);
+  const int lg2 = UPB_PRIVATE(_upb_Array_ElemSizeLg2)(arr);
   UPB_ASSERT(i < arr->size);
   memcpy(&ret, data + (i << lg2), 1 << lg2);
   return ret;
@@ -41,7 +41,7 @@ upb_MessageValue upb_Array_Get(const upb_Array* arr, size_t i) {
 
 void upb_Array_Set(upb_Array* arr, size_t i, upb_MessageValue val) {
   char* data = _upb_array_ptr(arr);
-  const int lg2 = _upb_Array_ElemSizeLg2(arr);
+  const int lg2 = UPB_PRIVATE(_upb_Array_ElemSizeLg2)(arr);
   UPB_ASSERT(i < arr->size);
   memcpy(data + (i << lg2), &val, 1 << lg2);
 }
@@ -57,7 +57,7 @@ bool upb_Array_Append(upb_Array* arr, upb_MessageValue val, upb_Arena* arena) {
 
 void upb_Array_Move(upb_Array* arr, size_t dst_idx, size_t src_idx,
                     size_t count) {
-  const int lg2 = _upb_Array_ElemSizeLg2(arr);
+  const int lg2 = UPB_PRIVATE(_upb_Array_ElemSizeLg2)(arr);
   char* data = _upb_array_ptr(arr);
   memmove(&data[dst_idx << lg2], &data[src_idx << lg2], count << lg2);
 }
@@ -94,20 +94,19 @@ bool upb_Array_Resize(upb_Array* arr, size_t size, upb_Arena* arena) {
   }
   const size_t newsize = arr->size;
   if (newsize > oldsize) {
-    const int lg2 = _upb_Array_ElemSizeLg2(arr);
+    const int lg2 = UPB_PRIVATE(_upb_Array_ElemSizeLg2)(arr);
     char* data = _upb_array_ptr(arr);
     memset(data + (oldsize << lg2), 0, (newsize - oldsize) << lg2);
   }
   return true;
 }
 
-// EVERYTHING BELOW THIS LINE IS INTERNAL - DO NOT USE /////////////////////////
-
-bool _upb_array_realloc(upb_Array* arr, size_t min_capacity, upb_Arena* arena) {
-  size_t new_capacity = UPB_MAX(arr->capacity, 4);
-  const int lg2 = _upb_Array_ElemSizeLg2(arr);
-  size_t old_bytes = arr->capacity << lg2;
-  void* ptr = _upb_array_ptr(arr);
+bool UPB_PRIVATE(_upb_Array_Realloc)(upb_Array* array, size_t min_capacity,
+                                     upb_Arena* arena) {
+  size_t new_capacity = UPB_MAX(array->UPB_PRIVATE(capacity), 4);
+  const int lg2 = UPB_PRIVATE(_upb_Array_ElemSizeLg2)(array);
+  size_t old_bytes = array->UPB_PRIVATE(capacity) << lg2;
+  void* ptr = _upb_array_ptr(array);
 
   // Log2 ceiling of size.
   while (new_capacity < min_capacity) new_capacity *= 2;
@@ -116,7 +115,7 @@ bool _upb_array_realloc(upb_Array* arr, size_t min_capacity, upb_Arena* arena) {
   ptr = upb_Arena_Realloc(arena, ptr, old_bytes, new_bytes);
   if (!ptr) return false;
 
-  _upb_Array_SetTaggedPtr(arr, ptr, lg2);
-  arr->capacity = new_capacity;
+  UPB_PRIVATE(_upb_Array_SetTaggedPtr)(array, ptr, lg2);
+  array->UPB_PRIVATE(capacity) = new_capacity;
   return true;
 }
diff --git a/upb/message/copy.c b/upb/message/copy.c
index 62e8aa821d..52f8f67767 100644
--- a/upb/message/copy.c
+++ b/upb/message/copy.c
@@ -143,7 +143,7 @@ upb_Array* upb_Array_DeepClone(const upb_Array* array, upb_CType value_type,
                                const upb_MiniTable* sub, upb_Arena* arena) {
   size_t size = array->size;
   upb_Array* cloned_array =
-      _upb_Array_New(arena, size, upb_CType_SizeLg2(value_type));
+      UPB_PRIVATE(_upb_Array_New)(arena, size, upb_CType_SizeLg2(value_type));
   if (!cloned_array) {
     return NULL;
   }
diff --git a/upb/message/internal/array.h b/upb/message/internal/array.h
index dc68a66baa..a99e2e44c8 100644
--- a/upb/message/internal/array.h
+++ b/upb/message/internal/array.h
@@ -35,81 +35,82 @@ struct upb_Array {
   // Bit #2 contains the frozen/immutable flag (currently unimplemented).
   uintptr_t data;
 
-  size_t size;      // The number of elements in the array.
-  size_t capacity;  // Allocated storage. Measured in elements.
+  size_t size;                   // The number of elements in the array.
+  size_t UPB_PRIVATE(capacity);  // Allocated storage. Measured in elements.
 };
 // LINT.ThenChange(GoogleInternalName1)
 
-UPB_INLINE void _upb_Array_SetTaggedPtr(upb_Array* arr, void* data,
-                                        size_t lg2) {
+UPB_INLINE void UPB_PRIVATE(_upb_Array_SetTaggedPtr)(upb_Array* array,
+                                                     void* data, size_t lg2) {
   UPB_ASSERT(lg2 != 1);
   UPB_ASSERT(lg2 <= 4);
   const size_t bits = lg2 - (lg2 != 0);
-  arr->data = (uintptr_t)data | bits;
+  array->data = (uintptr_t)data | bits;
 }
 
-UPB_INLINE size_t _upb_Array_ElemSizeLg2(const upb_Array* arr) {
-  const size_t bits = arr->data & _UPB_ARRAY_MASK_LG2;
+UPB_INLINE size_t UPB_PRIVATE(_upb_Array_ElemSizeLg2)(const upb_Array* array) {
+  const size_t bits = array->data & _UPB_ARRAY_MASK_LG2;
   const size_t lg2 = bits + (bits != 0);
   return lg2;
 }
 
-UPB_INLINE const void* _upb_array_constptr(const upb_Array* arr) {
-  _upb_Array_ElemSizeLg2(arr);  // Check assertions.
-  return (void*)(arr->data & ~(uintptr_t)_UPB_ARRAY_MASK_ALL);
+UPB_INLINE const void* _upb_array_constptr(const upb_Array* array) {
+  UPB_PRIVATE(_upb_Array_ElemSizeLg2)(array);  // Check assertions.
+  return (void*)(array->data & ~(uintptr_t)_UPB_ARRAY_MASK_ALL);
 }
 
-UPB_INLINE void* _upb_array_ptr(upb_Array* arr) {
-  return (void*)_upb_array_constptr(arr);
+UPB_INLINE void* _upb_array_ptr(upb_Array* array) {
+  return (void*)_upb_array_constptr(array);
 }
 
-UPB_INLINE upb_Array* _upb_Array_New(upb_Arena* a, size_t init_capacity,
-                                     int elem_size_lg2) {
+UPB_INLINE upb_Array* UPB_PRIVATE(_upb_Array_New)(upb_Arena* arena,
+                                                  size_t init_capacity,
+                                                  int elem_size_lg2) {
   UPB_ASSERT(elem_size_lg2 != 1);
   UPB_ASSERT(elem_size_lg2 <= 4);
-  const size_t arr_size = UPB_ALIGN_UP(sizeof(upb_Array), UPB_MALLOC_ALIGN);
-  const size_t bytes = arr_size + (init_capacity << elem_size_lg2);
-  upb_Array* arr = (upb_Array*)upb_Arena_Malloc(a, bytes);
-  if (!arr) return NULL;
-  _upb_Array_SetTaggedPtr(arr, UPB_PTR_AT(arr, arr_size, void), elem_size_lg2);
-  arr->size = 0;
-  arr->capacity = init_capacity;
-  return arr;
+  const size_t array_size = UPB_ALIGN_UP(sizeof(upb_Array), UPB_MALLOC_ALIGN);
+  const size_t bytes = array_size + (init_capacity << elem_size_lg2);
+  upb_Array* array = (upb_Array*)upb_Arena_Malloc(arena, bytes);
+  if (!array) return NULL;
+  UPB_PRIVATE(_upb_Array_SetTaggedPtr)
+  (array, UPB_PTR_AT(array, array_size, void), elem_size_lg2);
+  array->size = 0;
+  array->UPB_PRIVATE(capacity) = init_capacity;
+  return array;
 }
 
 // Resizes the capacity of the array to be at least min_size.
-bool _upb_array_realloc(upb_Array* arr, size_t min_size, upb_Arena* arena);
+bool UPB_PRIVATE(_upb_Array_Realloc)(upb_Array* array, size_t min_size,
+                                     upb_Arena* arena);
 
-UPB_INLINE bool _upb_array_reserve(upb_Array* arr, size_t size,
-                                   upb_Arena* arena) {
-  if (arr->capacity < size) return _upb_array_realloc(arr, size, arena);
+UPB_INLINE bool UPB_PRIVATE(_upb_Array_Reserve)(upb_Array* array, size_t size,
+                                                upb_Arena* arena) {
+  if (array->UPB_PRIVATE(capacity) < size)
+    return UPB_PRIVATE(_upb_Array_Realloc)(array, size, arena);
   return true;
 }
 
 // Resize without initializing new elements.
-UPB_INLINE bool _upb_Array_ResizeUninitialized(upb_Array* arr, size_t size,
+UPB_INLINE bool _upb_Array_ResizeUninitialized(upb_Array* array, size_t size,
                                                upb_Arena* arena) {
-  UPB_ASSERT(size <= arr->size || arena);  // Allow NULL arena when shrinking.
-  if (!_upb_array_reserve(arr, size, arena)) return false;
-  arr->size = size;
+  UPB_ASSERT(size <= array->size || arena);  // Allow NULL arena when shrinking.
+  if (!UPB_PRIVATE(_upb_Array_Reserve)(array, size, arena)) return false;
+  array->size = size;
   return true;
 }
 
 // This function is intended for situations where elem_size is compile-time
 // constant or a known expression of the form (1 << lg2), so that the expression
 // i*elem_size does not result in an actual multiplication.
-UPB_INLINE void _upb_Array_Set(upb_Array* arr, size_t i, const void* data,
-                               size_t elem_size) {
-  UPB_ASSERT(i < arr->size);
-  UPB_ASSERT(elem_size == 1U << _upb_Array_ElemSizeLg2(arr));
-  char* arr_data = (char*)_upb_array_ptr(arr);
+UPB_INLINE void UPB_PRIVATE(_upb_Array_Set)(upb_Array* array, size_t i,
+                                            const void* data,
+                                            size_t elem_size) {
+  UPB_ASSERT(i < array->size);
+  UPB_ASSERT(elem_size == 1U << UPB_PRIVATE(_upb_Array_ElemSizeLg2)(array));
+  char* arr_data = (char*)_upb_array_ptr(array);
   memcpy(arr_data + (i * elem_size), data, elem_size);
 }
 
-UPB_INLINE void _upb_array_detach(const void* msg, size_t ofs) {
-  *UPB_PTR_AT(msg, ofs, upb_Array*) = NULL;
-}
-
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
diff --git a/upb/reflection/stage0/google/protobuf/descriptor.upb.h b/upb/reflection/stage0/google/protobuf/descriptor.upb.h
index 064a821d7d..b44602fb2e 100644
--- a/upb/reflection/stage0/google/protobuf/descriptor.upb.h
+++ b/upb/reflection/stage0/google/protobuf/descriptor.upb.h
@@ -328,7 +328,7 @@ UPB_INLINE struct google_protobuf_FileDescriptorProto* google_protobuf_FileDescr
   }
   struct google_protobuf_FileDescriptorProto* sub = (struct google_protobuf_FileDescriptorProto*)_upb_Message_New(google__protobuf__FileDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -746,7 +746,7 @@ UPB_INLINE bool google_protobuf_FileDescriptorProto_add_dependency(google_protob
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 UPB_INLINE google_protobuf_DescriptorProto** google_protobuf_FileDescriptorProto_mutable_message_type(google_protobuf_FileDescriptorProto* msg, size_t* size) {
@@ -772,7 +772,7 @@ UPB_INLINE struct google_protobuf_DescriptorProto* google_protobuf_FileDescripto
   }
   struct google_protobuf_DescriptorProto* sub = (struct google_protobuf_DescriptorProto*)_upb_Message_New(google__protobuf__DescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE google_protobuf_EnumDescriptorProto** google_protobuf_FileDescriptorProto_mutable_enum_type(google_protobuf_FileDescriptorProto* msg, size_t* size) {
@@ -798,7 +798,7 @@ UPB_INLINE struct google_protobuf_EnumDescriptorProto* google_protobuf_FileDescr
   }
   struct google_protobuf_EnumDescriptorProto* sub = (struct google_protobuf_EnumDescriptorProto*)_upb_Message_New(google__protobuf__EnumDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE google_protobuf_ServiceDescriptorProto** google_protobuf_FileDescriptorProto_mutable_service(google_protobuf_FileDescriptorProto* msg, size_t* size) {
@@ -824,7 +824,7 @@ UPB_INLINE struct google_protobuf_ServiceDescriptorProto* google_protobuf_FileDe
   }
   struct google_protobuf_ServiceDescriptorProto* sub = (struct google_protobuf_ServiceDescriptorProto*)_upb_Message_New(google__protobuf__ServiceDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE google_protobuf_FieldDescriptorProto** google_protobuf_FileDescriptorProto_mutable_extension(google_protobuf_FileDescriptorProto* msg, size_t* size) {
@@ -850,7 +850,7 @@ UPB_INLINE struct google_protobuf_FieldDescriptorProto* google_protobuf_FileDesc
   }
   struct google_protobuf_FieldDescriptorProto* sub = (struct google_protobuf_FieldDescriptorProto*)_upb_Message_New(google__protobuf__FieldDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE void google_protobuf_FileDescriptorProto_set_options(google_protobuf_FileDescriptorProto *msg, google_protobuf_FileOptions* value) {
@@ -898,7 +898,7 @@ UPB_INLINE bool google_protobuf_FileDescriptorProto_add_public_dependency(google
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 UPB_INLINE int32_t* google_protobuf_FileDescriptorProto_mutable_weak_dependency(google_protobuf_FileDescriptorProto* msg, size_t* size) {
@@ -922,7 +922,7 @@ UPB_INLINE bool google_protobuf_FileDescriptorProto_add_weak_dependency(google_p
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 UPB_INLINE void google_protobuf_FileDescriptorProto_set_syntax(google_protobuf_FileDescriptorProto *msg, upb_StringView value) {
@@ -1323,7 +1323,7 @@ UPB_INLINE struct google_protobuf_FieldDescriptorProto* google_protobuf_Descript
   }
   struct google_protobuf_FieldDescriptorProto* sub = (struct google_protobuf_FieldDescriptorProto*)_upb_Message_New(google__protobuf__FieldDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE google_protobuf_DescriptorProto** google_protobuf_DescriptorProto_mutable_nested_type(google_protobuf_DescriptorProto* msg, size_t* size) {
@@ -1349,7 +1349,7 @@ UPB_INLINE struct google_protobuf_DescriptorProto* google_protobuf_DescriptorPro
   }
   struct google_protobuf_DescriptorProto* sub = (struct google_protobuf_DescriptorProto*)_upb_Message_New(google__protobuf__DescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE google_protobuf_EnumDescriptorProto** google_protobuf_DescriptorProto_mutable_enum_type(google_protobuf_DescriptorProto* msg, size_t* size) {
@@ -1375,7 +1375,7 @@ UPB_INLINE struct google_protobuf_EnumDescriptorProto* google_protobuf_Descripto
   }
   struct google_protobuf_EnumDescriptorProto* sub = (struct google_protobuf_EnumDescriptorProto*)_upb_Message_New(google__protobuf__EnumDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE google_protobuf_DescriptorProto_ExtensionRange** google_protobuf_DescriptorProto_mutable_extension_range(google_protobuf_DescriptorProto* msg, size_t* size) {
@@ -1401,7 +1401,7 @@ UPB_INLINE struct google_protobuf_DescriptorProto_ExtensionRange* google_protobu
   }
   struct google_protobuf_DescriptorProto_ExtensionRange* sub = (struct google_protobuf_DescriptorProto_ExtensionRange*)_upb_Message_New(google__protobuf__DescriptorProto__ExtensionRange_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE google_protobuf_FieldDescriptorProto** google_protobuf_DescriptorProto_mutable_extension(google_protobuf_DescriptorProto* msg, size_t* size) {
@@ -1427,7 +1427,7 @@ UPB_INLINE struct google_protobuf_FieldDescriptorProto* google_protobuf_Descript
   }
   struct google_protobuf_FieldDescriptorProto* sub = (struct google_protobuf_FieldDescriptorProto*)_upb_Message_New(google__protobuf__FieldDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE void google_protobuf_DescriptorProto_set_options(google_protobuf_DescriptorProto *msg, google_protobuf_MessageOptions* value) {
@@ -1465,7 +1465,7 @@ UPB_INLINE struct google_protobuf_OneofDescriptorProto* google_protobuf_Descript
   }
   struct google_protobuf_OneofDescriptorProto* sub = (struct google_protobuf_OneofDescriptorProto*)_upb_Message_New(google__protobuf__OneofDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE google_protobuf_DescriptorProto_ReservedRange** google_protobuf_DescriptorProto_mutable_reserved_range(google_protobuf_DescriptorProto* msg, size_t* size) {
@@ -1491,7 +1491,7 @@ UPB_INLINE struct google_protobuf_DescriptorProto_ReservedRange* google_protobuf
   }
   struct google_protobuf_DescriptorProto_ReservedRange* sub = (struct google_protobuf_DescriptorProto_ReservedRange*)_upb_Message_New(google__protobuf__DescriptorProto__ReservedRange_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE upb_StringView* google_protobuf_DescriptorProto_mutable_reserved_name(google_protobuf_DescriptorProto* msg, size_t* size) {
@@ -1515,7 +1515,7 @@ UPB_INLINE bool google_protobuf_DescriptorProto_add_reserved_name(google_protobu
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 
@@ -1859,7 +1859,7 @@ UPB_INLINE struct google_protobuf_ExtensionRangeOptions_Declaration* google_prot
   }
   struct google_protobuf_ExtensionRangeOptions_Declaration* sub = (struct google_protobuf_ExtensionRangeOptions_Declaration*)_upb_Message_New(google__protobuf__ExtensionRangeOptions__Declaration_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE void google_protobuf_ExtensionRangeOptions_set_verification(google_protobuf_ExtensionRangeOptions *msg, int32_t value) {
@@ -1901,7 +1901,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_Extension
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -2578,7 +2578,7 @@ UPB_INLINE struct google_protobuf_EnumValueDescriptorProto* google_protobuf_Enum
   }
   struct google_protobuf_EnumValueDescriptorProto* sub = (struct google_protobuf_EnumValueDescriptorProto*)_upb_Message_New(google__protobuf__EnumValueDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE void google_protobuf_EnumDescriptorProto_set_options(google_protobuf_EnumDescriptorProto *msg, google_protobuf_EnumOptions* value) {
@@ -2616,7 +2616,7 @@ UPB_INLINE struct google_protobuf_EnumDescriptorProto_EnumReservedRange* google_
   }
   struct google_protobuf_EnumDescriptorProto_EnumReservedRange* sub = (struct google_protobuf_EnumDescriptorProto_EnumReservedRange*)_upb_Message_New(google__protobuf__EnumDescriptorProto__EnumReservedRange_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE upb_StringView* google_protobuf_EnumDescriptorProto_mutable_reserved_name(google_protobuf_EnumDescriptorProto* msg, size_t* size) {
@@ -2640,7 +2640,7 @@ UPB_INLINE bool google_protobuf_EnumDescriptorProto_add_reserved_name(google_pro
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 
@@ -2951,7 +2951,7 @@ UPB_INLINE struct google_protobuf_MethodDescriptorProto* google_protobuf_Service
   }
   struct google_protobuf_MethodDescriptorProto* sub = (struct google_protobuf_MethodDescriptorProto*)_upb_Message_New(google__protobuf__MethodDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE void google_protobuf_ServiceDescriptorProto_set_options(google_protobuf_ServiceDescriptorProto *msg, google_protobuf_ServiceOptions* value) {
@@ -3629,7 +3629,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_FileOptio
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -3851,7 +3851,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_MessageOp
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -4209,7 +4209,7 @@ UPB_INLINE bool google_protobuf_FieldOptions_add_targets(google_protobuf_FieldOp
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 UPB_INLINE google_protobuf_FieldOptions_EditionDefault** google_protobuf_FieldOptions_mutable_edition_defaults(google_protobuf_FieldOptions* msg, size_t* size) {
@@ -4235,7 +4235,7 @@ UPB_INLINE struct google_protobuf_FieldOptions_EditionDefault* google_protobuf_F
   }
   struct google_protobuf_FieldOptions_EditionDefault* sub = (struct google_protobuf_FieldOptions_EditionDefault*)_upb_Message_New(google__protobuf__FieldOptions__EditionDefault_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE void google_protobuf_FieldOptions_set_features(google_protobuf_FieldOptions *msg, google_protobuf_FeatureSet* value) {
@@ -4273,7 +4273,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_FieldOpti
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -4475,7 +4475,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_OneofOpti
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -4659,7 +4659,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_EnumOptio
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -4824,7 +4824,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_EnumValue
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -4970,7 +4970,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_ServiceOp
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -5135,7 +5135,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption* google_protobuf_MethodOpt
   }
   struct google_protobuf_UninterpretedOption* sub = (struct google_protobuf_UninterpretedOption*)_upb_Message_New(google__protobuf__UninterpretedOption_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -5325,7 +5325,7 @@ UPB_INLINE struct google_protobuf_UninterpretedOption_NamePart* google_protobuf_
   }
   struct google_protobuf_UninterpretedOption_NamePart* sub = (struct google_protobuf_UninterpretedOption_NamePart*)_upb_Message_New(google__protobuf__UninterpretedOption__NamePart_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE void google_protobuf_UninterpretedOption_set_identifier_value(google_protobuf_UninterpretedOption *msg, upb_StringView value) {
@@ -5705,7 +5705,7 @@ UPB_INLINE struct google_protobuf_FeatureSetDefaults_FeatureSetEditionDefault* g
   }
   struct google_protobuf_FeatureSetDefaults_FeatureSetEditionDefault* sub = (struct google_protobuf_FeatureSetDefaults_FeatureSetEditionDefault*)_upb_Message_New(google__protobuf__FeatureSetDefaults__FeatureSetEditionDefault_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE void google_protobuf_FeatureSetDefaults_set_minimum_edition(google_protobuf_FeatureSetDefaults *msg, int32_t value) {
@@ -5896,7 +5896,7 @@ UPB_INLINE struct google_protobuf_SourceCodeInfo_Location* google_protobuf_Sourc
   }
   struct google_protobuf_SourceCodeInfo_Location* sub = (struct google_protobuf_SourceCodeInfo_Location*)_upb_Message_New(google__protobuf__SourceCodeInfo__Location_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -6098,7 +6098,7 @@ UPB_INLINE bool google_protobuf_SourceCodeInfo_Location_add_path(google_protobuf
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 UPB_INLINE int32_t* google_protobuf_SourceCodeInfo_Location_mutable_span(google_protobuf_SourceCodeInfo_Location* msg, size_t* size) {
@@ -6122,7 +6122,7 @@ UPB_INLINE bool google_protobuf_SourceCodeInfo_Location_add_span(google_protobuf
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 UPB_INLINE void google_protobuf_SourceCodeInfo_Location_set_leading_comments(google_protobuf_SourceCodeInfo_Location *msg, upb_StringView value) {
@@ -6154,7 +6154,7 @@ UPB_INLINE bool google_protobuf_SourceCodeInfo_Location_add_leading_detached_com
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 
@@ -6254,7 +6254,7 @@ UPB_INLINE struct google_protobuf_GeneratedCodeInfo_Annotation* google_protobuf_
   }
   struct google_protobuf_GeneratedCodeInfo_Annotation* sub = (struct google_protobuf_GeneratedCodeInfo_Annotation*)_upb_Message_New(google__protobuf__GeneratedCodeInfo__Annotation_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -6412,7 +6412,7 @@ UPB_INLINE bool google_protobuf_GeneratedCodeInfo_Annotation_add_path(google_pro
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 UPB_INLINE void google_protobuf_GeneratedCodeInfo_Annotation_set_source_file(google_protobuf_GeneratedCodeInfo_Annotation *msg, upb_StringView value) {
diff --git a/upb/wire/decode.c b/upb/wire/decode.c
index f33ed06cc4..c2525ea6ac 100644
--- a/upb/wire/decode.c
+++ b/upb/wire/decode.c
@@ -112,8 +112,9 @@ static void _upb_Decoder_VerifyUtf8(upb_Decoder* d, const char* buf, int len) {
 }
 
 static bool _upb_Decoder_Reserve(upb_Decoder* d, upb_Array* arr, size_t elem) {
-  bool need_realloc = arr->capacity - arr->size < elem;
-  if (need_realloc && !_upb_array_realloc(arr, arr->size + elem, &d->arena)) {
+  bool need_realloc = arr->UPB_PRIVATE(capacity) - arr->size < elem;
+  if (need_realloc &&
+      !UPB_PRIVATE(_upb_Array_Realloc)(arr, arr->size + elem, &d->arena)) {
     _upb_Decoder_ErrorJmp(d, kUpb_DecodeStatus_OutOfMemory);
   }
   return need_realloc;
@@ -477,7 +478,7 @@ upb_Array* _upb_Decoder_CreateArray(upb_Decoder* d,
                                     const upb_MiniTableField* field) {
   const upb_FieldType field_type = field->UPB_PRIVATE(descriptortype);
   const size_t lg2 = upb_FieldType_SizeLg2(field_type);
-  upb_Array* ret = _upb_Array_New(&d->arena, 4, lg2);
+  upb_Array* ret = UPB_PRIVATE(_upb_Array_New)(&d->arena, 4, lg2);
   if (!ret) _upb_Decoder_ErrorJmp(d, kUpb_DecodeStatus_OutOfMemory);
   return ret;
 }
diff --git a/upb/wire/decode_fast.c b/upb/wire/decode_fast.c
index 0ce3feff78..5a412ef308 100644
--- a/upb/wire/decode_fast.c
+++ b/upb/wire/decode_fast.c
@@ -165,15 +165,15 @@ UPB_FORCEINLINE
 static void* fastdecode_resizearr(upb_Decoder* d, void* dst,
                                   fastdecode_arr* farr, int valbytes) {
   if (UPB_UNLIKELY(dst == farr->end)) {
-    size_t old_capacity = farr->arr->capacity;
+    size_t old_capacity = farr->arr->UPB_PRIVATE(capacity);
     size_t old_bytes = old_capacity * valbytes;
     size_t new_capacity = old_capacity * 2;
     size_t new_bytes = new_capacity * valbytes;
     char* old_ptr = _upb_array_ptr(farr->arr);
     char* new_ptr = upb_Arena_Realloc(&d->arena, old_ptr, old_bytes, new_bytes);
     uint8_t elem_size_lg2 = __builtin_ctz(valbytes);
-    _upb_Array_SetTaggedPtr(farr->arr, new_ptr, elem_size_lg2);
-    farr->arr->capacity = new_capacity;
+    UPB_PRIVATE(_upb_Array_SetTaggedPtr)(farr->arr, new_ptr, elem_size_lg2);
+    farr->arr->UPB_PRIVATE(capacity) = new_capacity;
     dst = (void*)(new_ptr + (old_capacity * valbytes));
     farr->end = (void*)(new_ptr + (new_capacity * valbytes));
   }
@@ -255,13 +255,13 @@ static void* fastdecode_getfield(upb_Decoder* d, const char* ptr,
       *(uint32_t*)msg |= *hasbits;
       *hasbits = 0;
       if (UPB_LIKELY(!*arr_p)) {
-        farr->arr = _upb_Array_New(&d->arena, 8, elem_size_lg2);
+        farr->arr = UPB_PRIVATE(_upb_Array_New)(&d->arena, 8, elem_size_lg2);
         *arr_p = farr->arr;
       } else {
         farr->arr = *arr_p;
       }
       begin = _upb_array_ptr(farr->arr);
-      farr->end = begin + (farr->arr->capacity * valbytes);
+      farr->end = begin + (farr->arr->UPB_PRIVATE(capacity) * valbytes);
       *data = _upb_FastDecoder_LoadTag(ptr);
       return begin + (farr->arr->size * valbytes);
     }
@@ -540,7 +540,8 @@ TAGBYTES(p)
   int elems = size / valbytes;                                              \
                                                                             \
   if (UPB_LIKELY(!arr)) {                                                   \
-    *arr_p = arr = _upb_Array_New(&d->arena, elems, elem_size_lg2);         \
+    *arr_p = arr =                                                          \
+        UPB_PRIVATE(_upb_Array_New)(&d->arena, elems, elem_size_lg2);       \
     if (!arr) {                                                             \
       _upb_FastDecoder_ErrorJmp(d, kUpb_DecodeStatus_Malformed);            \
     }                                                                       \
diff --git a/upb_generator/protoc-gen-upb.cc b/upb_generator/protoc-gen-upb.cc
index fa60e83603..f5c5056739 100644
--- a/upb_generator/protoc-gen-upb.cc
+++ b/upb_generator/protoc-gen-upb.cc
@@ -690,7 +690,7 @@ void GenerateRepeatedSetters(upb::FieldDefPtr field, const DefPoolPair& pools,
             }
             struct $0* sub = (struct $0*)_upb_Message_New($3, arena);
             if (!arr || !sub) return NULL;
-            _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+            UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
             return sub;
           }
         )cc",
@@ -706,7 +706,7 @@ void GenerateRepeatedSetters(upb::FieldDefPtr field, const DefPoolPair& pools,
             if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
               return false;
             }
-            _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+            UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
             return true;
           }
         )cc",
diff --git a/upb_generator/stage0/google/protobuf/compiler/plugin.upb.h b/upb_generator/stage0/google/protobuf/compiler/plugin.upb.h
index 1c5e100f57..e706b9b7f9 100644
--- a/upb_generator/stage0/google/protobuf/compiler/plugin.upb.h
+++ b/upb_generator/stage0/google/protobuf/compiler/plugin.upb.h
@@ -351,7 +351,7 @@ UPB_INLINE bool google_protobuf_compiler_CodeGeneratorRequest_add_file_to_genera
   if (!arr || !_upb_Array_ResizeUninitialized(arr, arr->size + 1, arena)) {
     return false;
   }
-  _upb_Array_Set(arr, arr->size - 1, &val, sizeof(val));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &val, sizeof(val));
   return true;
 }
 UPB_INLINE void google_protobuf_compiler_CodeGeneratorRequest_set_parameter(google_protobuf_compiler_CodeGeneratorRequest *msg, upb_StringView value) {
@@ -393,7 +393,7 @@ UPB_INLINE struct google_protobuf_FileDescriptorProto* google_protobuf_compiler_
   }
   struct google_protobuf_FileDescriptorProto* sub = (struct google_protobuf_FileDescriptorProto*)_upb_Message_New(google__protobuf__FileDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 UPB_INLINE struct google_protobuf_FileDescriptorProto** google_protobuf_compiler_CodeGeneratorRequest_mutable_source_file_descriptors(google_protobuf_compiler_CodeGeneratorRequest* msg, size_t* size) {
@@ -419,7 +419,7 @@ UPB_INLINE struct google_protobuf_FileDescriptorProto* google_protobuf_compiler_
   }
   struct google_protobuf_FileDescriptorProto* sub = (struct google_protobuf_FileDescriptorProto*)_upb_Message_New(google__protobuf__FileDescriptorProto_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }
 
@@ -557,7 +557,7 @@ UPB_INLINE struct google_protobuf_compiler_CodeGeneratorResponse_File* google_pr
   }
   struct google_protobuf_compiler_CodeGeneratorResponse_File* sub = (struct google_protobuf_compiler_CodeGeneratorResponse_File*)_upb_Message_New(google__protobuf__compiler__CodeGeneratorResponse__File_msg_init(), arena);
   if (!arr || !sub) return NULL;
-  _upb_Array_Set(arr, arr->size - 1, &sub, sizeof(sub));
+  UPB_PRIVATE(_upb_Array_Set)(arr, arr->size - 1, &sub, sizeof(sub));
   return sub;
 }