Make PY_UNWIND available as a local event

We make the PY_UNWIND monitoring event available as a code-local
event to allow trapping on function exit events when an exception
bubbles up. This complements the PY_RETURN event by allowing to
catch any function exit event.

Author: P403n1x87

Include/cpython/monitoring.h

@@ -9,7 +9,7 @@ extern "C" {
 
 
 /* Local events.
- * These require bytecode instrumentation */
+ * Some of these require bytecode instrumentation */
 
 #define PY_MONITORING_EVENT_PY_START 0
 #define PY_MONITORING_EVENT_PY_RESUME 1
@@ -22,15 +22,18 @@ extern "C" {
 #define PY_MONITORING_EVENT_BRANCH_LEFT 8
 #define PY_MONITORING_EVENT_BRANCH_RIGHT 9
 #define PY_MONITORING_EVENT_STOP_ITERATION 10
+#define PY_MONITORING_EVENT_PY_UNWIND 11
 
+// TODO: PY_UNWIND requires no instrumentation so this definition is not
+// entirely correct.
 #define PY_MONITORING_IS_INSTRUMENTED_EVENT(ev) \
-    ((ev) < _PY_MONITORING_LOCAL_EVENTS)
+((ev) <= _PY_MONITORING_LOCAL_EVENTS)
+
 
 /* Other events, mainly exceptions */
 
-#define PY_MONITORING_EVENT_RAISE 11
 #define PY_MONITORING_EVENT_EXCEPTION_HANDLED 12
-#define PY_MONITORING_EVENT_PY_UNWIND 13
+#define PY_MONITORING_EVENT_RAISE 13
 #define PY_MONITORING_EVENT_PY_THROW 14
 #define PY_MONITORING_EVENT_RERAISE 15
 

Include/internal/pycore_instruments.h

@@ -74,7 +74,7 @@ extern PyObject _PyInstrumentation_DISABLE;
 /* Total tool ids available */
 #define  PY_MONITORING_TOOL_IDS 8
 /* Count of all local monitoring events */
-#define  _PY_MONITORING_LOCAL_EVENTS 11
+#define  _PY_MONITORING_LOCAL_EVENTS 12
 /* Count of all "real" monitoring events (not derived from other events) */
 #define _PY_MONITORING_UNGROUPED_EVENTS 16
 /* Count of all  monitoring events */

Python/ceval.c

@@ -2615,8 +2615,10 @@ monitor_unwind(PyThreadState *tstate,
                _PyInterpreterFrame *frame,
                _Py_CODEUNIT *instr)
 {
-    if (no_tools_for_global_event(tstate, PY_MONITORING_EVENT_PY_UNWIND)) {
-        return;
+    if (no_tools_for_local_event(tstate, frame, PY_MONITORING_EVENT_PY_UNWIND)) {
+        if (no_tools_for_global_event(tstate, PY_MONITORING_EVENT_PY_UNWIND)) {
+            return;
+        }
     }
     do_monitor_exc(tstate, frame, instr, PY_MONITORING_EVENT_PY_UNWIND);
 }