[3.12] gh-129838: Don't redefine _Py_NO_SANITIZE_UNDEFINED (GH-129839) (#130365)

miss-islington · collinfunk · web-flow · commit f314cc4db5a6 · 2025-02-20T16:20:27.000Z
gh-129838: Don't redefine _Py_NO_SANITIZE_UNDEFINED (GH-129839) Newer GCC versions accept both __attribute__((no_sanitize("undefined"))) and __attribute__((no_sanitize_undefined)) so check that the macro is not already defined. (cherry picked from commit 568db40) Co-authored-by: Collin Funk <collin.funk1@gmail.com>
diff --git a/Misc/NEWS.d/next/Build/2025-02-07-21-20-21.gh-issue-129838.fkuiEc.rst b/Misc/NEWS.d/next/Build/2025-02-07-21-20-21.gh-issue-129838.fkuiEc.rst
@@ -0,0 +1,2 @@
+Don't redefine ``_Py_NO_SANITIZE_UNDEFINED`` when compiling with a recent
+GCC version and undefined sanitizer enabled.
diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
@@ -29,14 +29,15 @@
 #define PUTS(fd, str) _Py_write_noraise(fd, str, strlen(str))
 
 
-// clang uses __attribute__((no_sanitize("undefined")))
-// GCC 4.9+ uses __attribute__((no_sanitize_undefined))
-#if defined(__has_feature)  // Clang
+// Clang and GCC 9.0+ use __attribute__((no_sanitize("undefined")))
+#if defined(__has_feature)
 #  if __has_feature(undefined_behavior_sanitizer)
 #    define _Py_NO_SANITIZE_UNDEFINED __attribute__((no_sanitize("undefined")))
 #  endif
 #endif
-#if defined(__GNUC__) \
+
+// GCC 4.9+ uses __attribute__((no_sanitize_undefined))
+#if !defined(_Py_NO_SANITIZE_UNDEFINED) && defined(__GNUC__) \
     && ((__GNUC__ >= 5) || (__GNUC__ == 4) && (__GNUC_MINOR__ >= 9))
 #  define _Py_NO_SANITIZE_UNDEFINED __attribute__((no_sanitize_undefined))
 #endif

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Don't redefine ``_Py_NO_SANITIZE_UNDEFINED`` when compiling with a recent
	`2`	`+GCC version and undefined sanitizer enabled.`