diff --git a/Include/internal/pycore_pyarena.h b/Include/internal/pycore_pyarena.h
index 6bd926a95cd..1f07479fb2c 100644
--- a/Include/internal/pycore_pyarena.h
+++ b/Include/internal/pycore_pyarena.h
@@ -1,7 +1,4 @@
-/* An arena-like memory interface for the compiler.
- *
- * Export symbols for test_peg_generator.
- */
+// An arena-like memory interface for the compiler.
 
 #ifndef Py_INTERNAL_PYARENA_H
 #define Py_INTERNAL_PYARENA_H
@@ -15,50 +12,55 @@ extern "C" {
 
 typedef struct _arena PyArena;
 
-/* _PyArena_New() and _PyArena_Free() create a new arena and free it,
-   respectively.  Once an arena has been created, it can be used
-   to allocate memory via _PyArena_Malloc().  Pointers to PyObject can
-   also be registered with the arena via _PyArena_AddPyObject(), and the
-   arena will ensure that the PyObjects stay alive at least until
-   _PyArena_Free() is called.  When an arena is freed, all the memory it
-   allocated is freed, the arena releases internal references to registered
-   PyObject*, and none of its pointers are valid.
-   XXX (tim) What does "none of its pointers are valid" mean?  Does it
-   XXX mean that pointers previously obtained via _PyArena_Malloc() are
-   XXX no longer valid?  (That's clearly true, but not sure that's what
-   XXX the text is trying to say.)
+// _PyArena_New() and _PyArena_Free() create a new arena and free it,
+// respectively.  Once an arena has been created, it can be used
+// to allocate memory via _PyArena_Malloc().  Pointers to PyObject can
+// also be registered with the arena via _PyArena_AddPyObject(), and the
+// arena will ensure that the PyObjects stay alive at least until
+// _PyArena_Free() is called.  When an arena is freed, all the memory it
+// allocated is freed, the arena releases internal references to registered
+// PyObject*, and none of its pointers are valid.
+// XXX (tim) What does "none of its pointers are valid" mean?  Does it
+// XXX mean that pointers previously obtained via _PyArena_Malloc() are
+// XXX no longer valid?  (That's clearly true, but not sure that's what
+// XXX the text is trying to say.)
+//
+// _PyArena_New() returns an arena pointer.  On error, it
+// returns a negative number and sets an exception.
+// XXX (tim):  Not true.  On error, _PyArena_New() actually returns NULL,
+// XXX and looks like it may or may not set an exception (e.g., if the
+// XXX internal PyList_New(0) returns NULL, _PyArena_New() passes that on
+// XXX and an exception is set; OTOH, if the internal
+// XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but
+// XXX an exception is not set in that case).
+//
+// Export for test_peg_generator
+PyAPI_FUNC(PyArena*) _PyArena_New(void);
 
-   _PyArena_New() returns an arena pointer.  On error, it
-   returns a negative number and sets an exception.
-   XXX (tim):  Not true.  On error, _PyArena_New() actually returns NULL,
-   XXX and looks like it may or may not set an exception (e.g., if the
-   XXX internal PyList_New(0) returns NULL, _PyArena_New() passes that on
-   XXX and an exception is set; OTOH, if the internal
-   XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but
-   XXX an exception is not set in that case).
-*/
-extern PyArena* _PyArena_New(void);
-extern void _PyArena_Free(PyArena *);
+// Export for test_peg_generator
+PyAPI_FUNC(void) _PyArena_Free(PyArena *);
 
-/* Mostly like malloc(), return the address of a block of memory spanning
- * `size` bytes, or return NULL (without setting an exception) if enough
- * new memory can't be obtained.  Unlike malloc(0), _PyArena_Malloc() with
- * size=0 does not guarantee to return a unique pointer (the pointer
- * returned may equal one or more other pointers obtained from
- * _PyArena_Malloc()).
- * Note that pointers obtained via _PyArena_Malloc() must never be passed to
- * the system free() or realloc(), or to any of Python's similar memory-
- * management functions.  _PyArena_Malloc()-obtained pointers remain valid
- * until _PyArena_Free(ar) is called, at which point all pointers obtained
- * from the arena `ar` become invalid simultaneously.
- */
-extern void* _PyArena_Malloc(PyArena *, size_t size);
+// Mostly like malloc(), return the address of a block of memory spanning
+// `size` bytes, or return NULL (without setting an exception) if enough
+// new memory can't be obtained.  Unlike malloc(0), _PyArena_Malloc() with
+// size=0 does not guarantee to return a unique pointer (the pointer
+// returned may equal one or more other pointers obtained from
+// _PyArena_Malloc()).
+// Note that pointers obtained via _PyArena_Malloc() must never be passed to
+// the system free() or realloc(), or to any of Python's similar memory-
+// management functions.  _PyArena_Malloc()-obtained pointers remain valid
+// until _PyArena_Free(ar) is called, at which point all pointers obtained
+// from the arena `ar` become invalid simultaneously.
+//
+// Export for test_peg_generator
+PyAPI_FUNC(void*) _PyArena_Malloc(PyArena *, size_t size);
 
-/* This routine isn't a proper arena allocation routine.  It takes
- * a PyObject* and records it so that it can be DECREFed when the
- * arena is freed.
- */
-extern int _PyArena_AddPyObject(PyArena *, PyObject *);
+// This routine isn't a proper arena allocation routine.  It takes
+// a PyObject* and records it so that it can be DECREFed when the
+// arena is freed.
+//
+// Export for test_peg_generator
+PyAPI_FUNC(int) _PyArena_AddPyObject(PyArena *, PyObject *);
 
 #ifdef __cplusplus
 }