gh-111178: Skip undefined behavior checks in _PyPegen_lookahead() (#131714)

vstinner · web-flow · commit 379688452845 · 2025-03-27T10:03:58.000+01:00
For example, expression_rule() return type is 'expr_ty', whereas
_PyPegen_lookahead() uses 'void*'.
diff --git 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;
 }

Original file line number	Diff line number	Diff line change
`@@ -406,11 +406,14 @@ _PyPegen_lookahead_with_int(int positive, Token (func)(Parser , int), Parser *`
`406`	`406`	`return (res != NULL) == positive;`
`407`	`407`	`}`
`408`	`408`
`409`		`-int`
	`409`	`+// gh-111178: Use _Py_NO_SANITIZE_UNDEFINED to disable sanitizer checks on`
	`410`	`+// undefined behavior (UBsan) in this function, rather than changing 'func'`
	`411`	`+// callback API.`
	`412`	`+int _Py_NO_SANITIZE_UNDEFINED`
`410`	`413`	`_PyPegen_lookahead(int positive, void (func)(Parser ), Parser *p)`
`411`	`414`	`{`
`412`	`415`	`int mark = p->mark;`
`413`		`- void res = (void)func(p);`
	`416`	`+ void *res = func(p);`
`414`	`417`	`p->mark = mark;`
`415`	`418`	`return (res != NULL) == positive;`
`416`	`419`	`}`