Issue #9738: Document encodings of AST, compiler, parser and PyRun functions
diff --git a/Include/compile.h b/Include/compile.h
index 456a494..5ce5b77 100644
--- a/Include/compile.h
+++ b/Include/compile.h
@@ -30,8 +30,12 @@
 
 struct _mod; /* Declare the existence of this type */
 #define PyAST_Compile(mod, s, f, ar) PyAST_CompileEx(mod, s, f, -1, ar)
-PyAPI_FUNC(PyCodeObject *) PyAST_CompileEx(struct _mod *, const char *,
-					   PyCompilerFlags *, int, PyArena *);
+PyAPI_FUNC(PyCodeObject *) PyAST_CompileEx(
+    mod_ty mod,
+    const char *filename,       /* decoded from the filesystem encoding */
+    PyCompilerFlags *flags,
+    int optimize,
+    PyArena *arena);
 PyAPI_FUNC(PyFutureFeatures *) PyFuture_FromAST(struct _mod *, const char *);