From: Stan Ulbrych <stan@python.org>
Date: Mon, 29 Jun 2026 09:06:04 +0000 (+0200)
Subject: gh-152375: Fix undefined behaviour in the `INSTRUMENTED_JUMP` macro (#152376)
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cdec9acd63c33d9b822700de8f63eb94d86e1c93;p=thirdparty%2FPython%2Fcpython.git

gh-152375: Fix undefined behaviour in the `INSTRUMENTED_JUMP` macro (#152376)
---

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-27-10-05-12.gh-issue-152375.L-ZBk6.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-27-10-05-12.gh-issue-152375.L-ZBk6.rst
new file mode 100644
index 000000000000..db6ae3060d83
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-27-10-05-12.gh-issue-152375.L-ZBk6.rst
@@ -0,0 +1,2 @@
+Fix undefined behaviour when a :mod:`sys.monitoring` callback raised an
+exception while the program was following a branch or loop.
diff --git a/Python/ceval_macros.h b/Python/ceval_macros.h
index 0de4477426af..b13884bf8214 100644
--- a/Python/ceval_macros.h
+++ b/Python/ceval_macros.h
@@ -389,14 +389,15 @@ static void dtrace_function_return(_PyInterpreterFrame *);
 // for an exception handler, displaying the traceback, and so on
 #define INSTRUMENTED_JUMP(src, dest, event) \
 do { \
+    _Py_CODEUNIT *_dest = (dest); \
     if (tstate->tracing) {\
-        next_instr = dest; \
+        next_instr = _dest; \
     } else { \
         _PyFrame_SetStackPointer(frame, stack_pointer); \
-        next_instr = _Py_call_instrumentation_jump(this_instr, tstate, event, frame, src, dest); \
+        next_instr = _Py_call_instrumentation_jump(this_instr, tstate, event, frame, src, _dest); \
         stack_pointer = _PyFrame_GetStackPointer(frame); \
         if (next_instr == NULL) { \
-            next_instr = (dest)+1; \
+            next_instr = _dest + 1; \
             JUMP_TO_LABEL(error); \
         } \
     } \