pythongh-133157: remove usage of _Py_NO_SANITIZE_UNDEFINED in pyexpat

Co-Authored-By: Bénédikt Tran <[email protected]>

Author: encukou

Modules/pyexpat.c

@@ -98,7 +98,11 @@ typedef struct {
 
 #define CHARACTER_DATA_BUFFER_SIZE 8192
 
-typedef const void *xmlhandler;
+// A generic function type for storage.
+// To avoid undefined behavior, a handler needs to be cast to the correct
+// function type before it's called; see SETTER_WRAPPER below.
+typedef void (*xmlhandler)(void);
+
 typedef void (*xmlhandlersetter)(XML_Parser self, xmlhandler handler);
 
 struct HandlerInfo {
@@ -110,9 +114,7 @@ struct HandlerInfo {
 
 static struct HandlerInfo handler_info[64];
 
-// gh-111178: Use _Py_NO_SANITIZE_UNDEFINED, rather than using the exact
-// handler API for each handler.
-static inline void _Py_NO_SANITIZE_UNDEFINED
+static inline void
 CALL_XML_HANDLER_SETTER(const struct HandlerInfo *handler_info,
                         XML_Parser xml_parser, xmlhandler xml_handler)
 {
@@ -1365,7 +1367,7 @@ xmlparse_handler_setter(PyObject *op, PyObject *v, void *closure)
            elaborate system of handlers and state could remove the
            C handler more effectively. */
         if (handlernum == CharacterData && self->in_callback) {
-            c_handler = noop_character_data_handler;
+            c_handler = (xmlhandler)noop_character_data_handler;
         }
         v = NULL;
     }
@@ -2222,13 +2224,83 @@ clear_handlers(xmlparseobject *self, int initial)
     }
 }
 
+/* To avoid undefined behavior, a function needs to be *called* via a function
+ * pointer of the correct type.
+ * So, for each `XML_Set*` function, we define a wrapper that calls the
+ * `XML_Set*` with its argument cast to the appropriate type.
+ */
+
+typedef void (*parser_only)(void *);
+typedef int (*not_standalone)(void *);
+typedef void (*parser_and_data)(void *, const XML_Char *);
+typedef void (*parser_and_data_and_int)(void *, const XML_Char *, int);
+typedef void (*parser_and_data_and_data)(
+    void *, const XML_Char *, const XML_Char *);
+typedef void (*start_element)(void *, const XML_Char *, const XML_Char **);
+typedef void (*element_decl)(void *, const XML_Char *, XML_Content *);
+typedef void (*xml_decl)(
+    void *, const XML_Char *, const XML_Char *, int);
+typedef void (*start_doctype_decl)(
+    void *, const XML_Char *, const XML_Char *, const XML_Char *, int);
+typedef void (*notation_decl)(
+    void *,
+    const XML_Char *, const XML_Char *, const XML_Char *, const XML_Char *);
+typedef void (*attlist_decl)(
+    void *,
+    const XML_Char *, const XML_Char *, const XML_Char *, const XML_Char *,
+    int);
+typedef void (*unparsed_entity_decl)(
+    void *,
+    const XML_Char *, const XML_Char *,
+    const XML_Char *, const XML_Char *, const XML_Char *);
+typedef void (*entity_decl)(
+    void *,
+    const XML_Char *, int,
+    const XML_Char *, int,
+    const XML_Char *, const XML_Char *, const XML_Char *, const XML_Char *);
+typedef int (*external_entity_ref)(
+    XML_Parser,
+    const XML_Char *, const XML_Char *, const XML_Char *, const XML_Char *);
+
+#define SETTER_WRAPPER(NAME, TYPE)                                      \
+    static inline void                                                  \
+    my_Set ## NAME (XML_Parser parser, xmlhandler handler)              \
+    {                                                                   \
+        (void)XML_Set ## NAME (parser, (TYPE)handler);                  \
+    }
+
+SETTER_WRAPPER(StartElementHandler, start_element)
+SETTER_WRAPPER(EndElementHandler, parser_and_data)
+SETTER_WRAPPER(ProcessingInstructionHandler, parser_and_data_and_data)
+SETTER_WRAPPER(CharacterDataHandler, parser_and_data_and_int)
+SETTER_WRAPPER(UnparsedEntityDeclHandler, unparsed_entity_decl)
+SETTER_WRAPPER(NotationDeclHandler, notation_decl)
+SETTER_WRAPPER(StartNamespaceDeclHandler, parser_and_data_and_data)
+SETTER_WRAPPER(EndNamespaceDeclHandler, parser_and_data)
+SETTER_WRAPPER(CommentHandler, parser_and_data)
+SETTER_WRAPPER(StartCdataSectionHandler, parser_only)
+SETTER_WRAPPER(EndCdataSectionHandler, parser_only)
+SETTER_WRAPPER(DefaultHandler, parser_and_data_and_int)
+SETTER_WRAPPER(DefaultHandlerExpand, parser_and_data_and_int)
+SETTER_WRAPPER(NotStandaloneHandler, not_standalone)
+SETTER_WRAPPER(ExternalEntityRefHandler, external_entity_ref)
+SETTER_WRAPPER(StartDoctypeDeclHandler, start_doctype_decl)
+SETTER_WRAPPER(EndDoctypeDeclHandler, parser_only)
+SETTER_WRAPPER(EntityDeclHandler, entity_decl)
+SETTER_WRAPPER(XmlDeclHandler, xml_decl)
+SETTER_WRAPPER(ElementDeclHandler, element_decl)
+SETTER_WRAPPER(AttlistDeclHandler, attlist_decl)
+#if XML_COMBINED_VERSION >= 19504
+SETTER_WRAPPER(SkippedEntityHandler, parser_and_data_and_int)
+#endif
+
 static struct HandlerInfo handler_info[] = {
 
     // The cast to `xmlhandlersetter` is needed as the signature of XML
     // handler functions is not compatible with `xmlhandlersetter` since
     // their second parameter is narrower than a `const void *`.
 #define HANDLER_INFO(name) \
-    {#name, (xmlhandlersetter)XML_Set##name, my_##name},
+    {#name, (xmlhandlersetter)my_Set##name, (xmlhandler)my_##name},
 
     HANDLER_INFO(StartElementHandler)
     HANDLER_INFO(EndElementHandler)