From 52ca09f489c6f546982585096841c60561589240 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Tue, 25 Mar 2025 12:58:12 +0100
Subject: [PATCH] gh-111178: Skip undefined behavior checks in
 _PyPegen_lookahead()

For example, expression_rule() return type is 'expr_ty', whereas
_PyPegen_lookahead() uses 'void*'.
---
 Parser/pegen.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Parser/pegen.c b/Parser/pegen.c
index 87a9ba02274d9f..94d83786164b1e 100644
--- a/Parser/pegen.c
+++ b/Parser/pegen.c
@@ -406,11 +406,14 @@ _PyPegen_lookahead_with_int(int positive, Token *(func)(Parser *, int), Parser *
     return (res != NULL) == positive;
 }
 
-int
+// gh-111178: Use _Py_NO_SANITIZE_UNDEFINED to disable sanitizer checks on
+// undefined behavior (UBsan) in this function, rather than changing 'func'
+// callback API.
+int _Py_NO_SANITIZE_UNDEFINED
 _PyPegen_lookahead(int positive, void *(func)(Parser *), Parser *p)
 {
     int mark = p->mark;
-    void *res = (void*)func(p);
+    void *res = func(p);
     p->mark = mark;
     return (res != NULL) == positive;
 }